The CMS experiment at the LHC pp collider will collect a large sample of lepton-pair events with masses ranging from the Z peak to several TeV. The total cross-section at high energy relative to the Z cross section can be measured with systematic error below 1 %. This will allow to test the Standard Model at very high momentum transfers and to probe the electroweak radiative corrections up to 2 TeV. The high energy/luminosity of LHC offers a rich search field for new phenomena at the TeV scale: resonance formation (TeV strings, Z', scalar neutrinos), contact interactions, virtual graviton exchange in quantum gravity models with extra dimensions.
Authors:CMS Collaboration
Proposed speaker: Dimitri Bourilkov
Contact person:Dimitri T Bourilkov
(CERN),
Dimitri.Bourilkov@cern.ch
Sessions: PA-11 Search for New Particles and New Phenomena /
Supporting papers: CMS Note 2000/xxx, CERN, 2000 (in preparation}
Notes:
Results of a Fermilab study of the sensitivity for Higgs boson production at the upgraded Tevatron in Run II are presented. The study extends previous Tevatron results by combining all possible search channels, considering the production of higher mass Higgs bosons and interpreting the results in the context of supersymmetric Higgs production as well as Standard Model production.
Authors:CDF and DZero collaborations
Proposed speaker: Maria Teresa P. Roco
Contact person:Maria Teresa P Roco
(FERMILAB),
roco@fnal.gov
Sessions: PA-11 Search for New Particles and New Phenomena /
Supporting papers:
Notes:
Though LEP II direct searches still cannot exclude a chargino nearly degenerate with the lightest neutralino if their mass is only slightly above half of the Z boson mass, it can be excluded indirectly analyzing precision data. In this particular limit simple analytical formulas for oblique electroweak radiative corrections are presented.
Authors:M. Maltoni, M. I. Vysotsky
Proposed speaker: M. I. Vysotsky
Contact person:Mikhail I Vysotsky
(ITEP),
vysotsky@heron.itep.ru
Sessions: PA-11 Search for New Particles and New Phenomena / PL-07a Search for New Particles and New Phenomena (Results from e+e- Colliders)
Supporting papers:
Notes:
We consider single charged Higgs boson production in association with a W boson at high-energy muon colliders. We find that this process may allow sizeable cross-sections whose analogies at e+e- colliders would be very small. This mechanism provides an attractive new way of producing charged Higgs bosons at muon colliders, and is superior to the conventional methods in regions of parameter space.
Authors:A.G. Akeroyd, A. Arhrib, C. Dove
Proposed speaker: A.G. Akeroyd
Contact person:Andrew G Akeroyd
(KEK),
akeroyd@ccthmail.kek.jp
Sessions: PA-11 Search for New Particles and New Phenomena /
Supporting papers: Phys. Rev. D61, 071702(R) (hep-ph/9910287)
Notes:
A search for the decay B+ --> K+ K+ pi- was performed using data collected by the OPAL detector at LEP. These decays are strongly suppressed in the Standard Model but could occur with a higher branching ratio in supersymmetric models, especially in those with R-parity violating couplings. No evidence for a signal was observed and a 90% confidence level upper limit of 1.29 x 10^-4 was set for the branching ratio.
Authors:The OPAL collaboration
Proposed speaker:
Contact person:David J Miller
(CERN),
dave.miller@cern.ch
Sessions: PA-11 Search for New Particles and New Phenomena / PL-07a Search for New Particles and New Phenomena (Results from e+e- Colliders)
Supporting papers: CERN-EP/99-179 = OPAL PR301, Phys. Lett B476 (2000)233-242 = http://opal.web.cern.ch/Opal/pubs/paper/html/pr301.html
Notes:Also Parallel session 7, Heavy Flavour Physics; and Plenary Session 3 Heavy Flavour Physics
Searches for neutral Higgs bosons in the Standard Model and the MSSM have been performed using data collected by the DELPHI experiment at a centre-of-mass energy of 188.7 GeV, corresponding to an integrated luminosity of 158~pb$^{-1}$. These analyses are used, in combination with our results from lower energies, to set new 95\% confidence level lower mass bounds on the Standard Model Higgs boson (94.6 GeV/$c^2$) and on the lightest neutral scalar (82.6 GeV/$c^2$) and neutral pseudoscalar (84.1 GeV/$c^2$) Higgs bosons in a representative scan of the MSSM parameters. The results are also interpreted in the framework of a general two-Higgs doublet model.
Authors:DELPHI collaboration
Proposed speaker:
Contact person:Clara Matteuzzi
(),
Clara.Matteuzzi@cern.ch
Sessions: PA-11 Search for New Particles and New Phenomena / PL-07a Search for New Particles and New Phenomena (Results from e+e- Colliders)
Supporting papers: CERN-EP-2000-038
Notes:
A search for charginos and neutralinos, predicted by supersymmetric theories, is performed using a data sample of 182.1 inverse pico-barns taken at a centre-of-mass energy of 189 GeV with the OPAL detector at LEP. No evidence for chargino or neutralino production is found. Upper limits on chargino and neutralino pair production cross-sections are obtained as a function of the chargino mass, the lightest neutralino mass and the second lightest neutralino mass. Limits on the chargino and neutralino masses are inferred within the Constrained Minimal Supersymmetric Standard Model framework.
Authors:The OPAL collaboration
Proposed speaker:
Contact person:David J Miller
(CERN),
dave.miller@cern.ch
Sessions: PA-11 Search for New Particles and New Phenomena / PL-07a Search for New Particles and New Phenomena (Results from e+e- Colliders)
Supporting papers: CERN-EP/99-123, Accepted by Eur. Phys. J. C =http://opal.web.cern.ch/Opal/pubs/paper/html/pr291.html
Notes:
Searches for a scalar top quark and a scalar bottom quark have been performed using a data sample of 182 inverse pico-barns at a centre-of-mass energy of 189 GeV collected with the OPAL detector at LEP. No evidence for a signal was found. The 95% C.L. lower limit on the scalar top quark mass is 90.3 GeV if the mixing angle between the supersymmetric partners of the left- and right-handed states of the top quark is zero. In the worst case, when the scalar top quark decouples from the Z boson, the lower limit is 87.2 GeV. These limits were obtained assuming that the scalar top quark decays into a charm quark and the lightest neutralino, and that the mass difference between the scalar top quark and the lightest neutralino is larger than 10 GeV. The complementary decay mode of the scalar top quark decaying into a bottom quark, a charged lepton and a scalar neutrino has also been studied. From a search for the scalar bottom quark, a mass limit of 88.6 GeV was obtained if the mass difference between the scalar bottom quark and the lightest neutralino is larger than 7 GeV.
Authors:The OPAL collaboration
Proposed speaker:
Contact person:David J Miller
(CERN),
dave.miller@cern.ch
Sessions: PA-11 Search for New Particles and New Phenomena / PL-07a Search for New Particles and New Phenomena (Results from e+e- Colliders)
Supporting papers: CERN-EP/99-036, Phys. Lett. B456 (1999) 95-106 =http://opal.web.cern.ch/Opal/pubs/paper/html/pr274.html
Notes:
A search for pair produced scalar fermions with couplings that violate R-parity has been performed using a data sample corresponding to an integrated luminosity of 56 pb^-1 at a centre-of-mass energy of sqrt{s}= 183 GeV collected with the OPAL detector at LEP. Searches for R-parity violating decays of charged sleptons, sneutrinos and stop quarks have been performed under the assumptions that the lightest supersymmetric particle decays promptly and that only one of the R-parity violating couplings is dominant for each of the decay modes considered. No significant excess of such events has been observed. Limits on the production cross-sections of scalar fermions in R-parity violating scenarios are obtained. Mass exclusion regions are also presented in the framework of the Constrained Minimal Supersymmetric Standard Model.
Authors:The OPAL collaboration
Proposed speaker:
Contact person:David J Miller
(CERN),
dave.miller@cern.ch
Sessions: PA-11 Search for New Particles and New Phenomena / PL-07a Search for New Particles and New Phenomena (Results from e+e- Colliders)
Supporting papers: CERN-EP/99-043, Eur. Phys. J. C12 (2000) 1-24 =http://opal.web.cern.ch/Opal/pubs/paper/html/pr275.html
Notes:
A search for pair-produced charginos and neutralinos with R-parity violating decays has been performed using a data sample corresponding to an integrated luminosity of 56 pb^-1 collected with the OPAL detector at LEP at a centre-of-mass energy of sqrt{s}= 183 GeV. The searches have been performed under the assumptions that the lightest supersymmetric particle promptly decays and that only one R-parity violating coupling is dominant for each of the decay modes considered. Such processes would yield multiple leptons, jets plus leptons, or multiple jets with or without significant missing energy in the final state. No excess of such events above Standard Model backgrounds has been observed. Limits are presented on the production cross-sections of gauginos and are also presented in the framework of the Minimal Supersymmetric Standard Model.
Authors:The OPAL collaboration
Proposed speaker:
Contact person:David J Miller
(CERN),
dave.miller@cern.ch
Sessions: PA-11 Search for New Particles and New Phenomena / PL-07a Search for New Particles and New Phenomena (Results from e+e- Colliders)
Supporting papers: CERN-EP/98-203, Eur. Phys. J. C11 (1999) 619-642 =http://opal.web.cern.ch/Opal/pubs/paper/html/pr269.html
Notes:
Searches for pair-produced gauginos and sfermions with R-parity violating decays via a coupling lambda prime or lambda double prime has been performed using a data sample corresponding to an integrated luminosity of 180 pb^-1 collected with the OPAL detector at LEP at a centre-of-mass energy of sqrt{s}= 189 GeV. The searches have been performed under the assumptions that the lightest supersymmetric particle promptly decays and that only one R-parity violating coupling is dominant for each of the decay modes considered. No excess of such events above Standard Model backgrounds has been observed. Limits are presented on the production cross-sections in R-parity violating scenarios and are interpreted in the framework of the Minimal Supersymmetric Standard Model (MSSM) as exclusions on sparticle masses and regions in the MSSM parameter space.
Authors:The OPAL collaboration
Proposed speaker:
Contact person:David J Miller
(CERN),
dave.miller@cern.ch
Sessions: PA-11 Search for New Particles and New Phenomena / PL-07a Search for New Particles and New Phenomena (Results from e+e- Colliders)
Supporting papers: OPAL Physics Note PN411 =http://opal.web.cern.ch/Opal/pubs/physnote/html/pn411.html
Notes:
Searches for pair-produced gauginos and scalar leptons with decays violating R-parity with lambda couplings have been performed using a data sample corresponding to an integrated luminosity of about 180 pb^-1 collected with the OPAL detector at a centre-of-mass energy of sqrt{s}= 189 GeV. The searches have been performed under the assumptions that the lightest supersymmetric particle promptly decays and that only one lambda_(ijk) R-parity violating coupling is dominant for each of the decay modes considered. Such processes would yield multiple leptons and jets plus leptons with or without significant missing energy in the final state. No excess of such events above Standard Model backgrounds has been observed.
Authors:The OPAL collaboration
Proposed speaker:
Contact person:David J Miller
(CERN),
dave.miller@cern.ch
Sessions: PA-11 Search for New Particles and New Phenomena / PL-07a Search for New Particles and New Phenomena (Results from e+e- Colliders)
Supporting papers: OPAL Physics Note PN394 =http://opal.web.cern.ch/Opal/pubs/physnote/html/pn394.html
Notes:
Searches for final states expected in models with light gravitinos have been performed, including experimental topologies with multi-leptons with missing energy, leptons and photons with missing energy, and jets and photons with missing energy. Cases with long-lived particles are also considered. No excess over the expectations from the Standard Model has been observed. Limits are placed on production cross-sections in the different experimental topologies.
Authors:The OPAL collaboration
Proposed speaker:
Contact person:David J Miller
(CERN),
dave.miller@cern.ch
Sessions: PA-11 Search for New Particles and New Phenomena / PL-07a Search for New Particles and New Phenomena (Results from e+e- Colliders)
Supporting papers: OPAL Physics Note PN397 =http://opal.web.cern.ch/Opal/pubs/physnote/html/pn397.html
Notes:
Searches for unstable neutral and charged heavy leptons, N and L, and for excited states of neutral and charged leptons, nu*, e*, mu*, and tau*, have been performed in e+e- collisions using data collected by the OPAL detector at LEP. The data analysed correspond to an integrated luminosity of about 58 inverse pico-barns at a centre-of-mass energy of 183 GeV, and about 10 inverse pico-barns each at 161 GeV and 172 GeV. No evidence for new particles was found. Lower limits on the masses of unstable heavy and excited leptons are derived. From the analysis of charged-current, neutral-current, and photonic decays of singly produced excited leptons, upper limits are determined for the ratio of the coupling to the compositeness scale, f/Lambda, for masses up to the kinematic limit. For excited leptons, the limits are established independently of the relative values of the coupling constants f and f'.
Authors:The OPAL collaboration
Proposed speaker:
Contact person:David J Miller
(CERN),
dave.miller@cern.ch
Sessions: PA-11 Search for New Particles and New Phenomena / PL-07a Search for New Particles and New Phenomena (Results from e+e- Colliders)
Supporting papers: CERN-EP/99-169, accepted by Eur. Phys. J. C =http://opal.web.cern.ch/Opal/pubs/paper/html/pr298.html
Notes:
A search for pair-produced leptoquarks has been performed using a sample of e+e- collision events collected by the OPAL detector at LEP at centre-of-mass energies of about 183~GeV. The data sample corresponds to an integrated luminosity of 55.9 inverse pico-barns. The leptoquarks were assumed to be produced via couplings to the photon and the Z and then to decay within a single fermion generation. No evidence for contributions from leptoquark pair production processes was observed. Lower limits on scalar and vector leptoquark masses are obtained. The existing limits are improved in the region of large decay branching ratio to quark-neutrino.
Authors:The OPAL collaboration
Proposed speaker:
Contact person:David J Miller
(CERN),
dave.miller@cern.ch
Sessions: PA-11 Search for New Particles and New Phenomena / PL-07a Search for New Particles and New Phenomena (Results from e+e- Colliders)
Supporting papers: CERN-EP/99-091, Eur. Phys. J. C13 (2000)15-27 =http://opal.web.cern.ch/Opal/pubs/paper/html/pr287.html
Notes:
Neutralino production and decays in bilinearly broken R-parity is studied. We demonstrate that the lightest neutralino typically decays inside the detector despite the small neutrino masses required for the explanation of the neutrino anomalies. In supergravity inspired models we show how the dominant decay modes restrict the possible parameter regions. This will give a first hint on the sfermion masses in this model. Moreover its decay patterns can be used to extract the parameters of the theory which control neutrino masses and mixings. Together with the neutrino-experiments, accelerators provide a stringent test of the theory.
Authors:M. Hirsch, W. Porod, J. Romao, J.W.F. Valle
Proposed speaker: W. Porod
Contact person:Werner Porod
(Universidad Valencia),
porod@ific.uv.es
Sessions: PA-11 Search for New Particles and New Phenomena /
Supporting papers:
Notes:
We discuss the phenomenology of stops in models where R-parity is broken by bilinear terms. In these models the lightest stop can have R-parity violating decays, such as into a b-quark and a lepton. We identify and study the regions of parameters where these decays have sizeable branching ratios. The consequences for the discovery and study of stops on colliders is discussed. Moreover, we show how the information on the branching ratios can be used to extract parameters of the theory which control neutrino masses and mixing angles.
Authors:M. Hirsch, W. Porod, D. Restrepo, J. Romao, J.W.F. Valle
Proposed speaker: W. Porod
Contact person:Werner Porod
(Universidad Valencia),
porod@ific.uv.es
Sessions: PA-11 Search for New Particles and New Phenomena /
Supporting papers:
Notes:W. Porod, D. Restrepo, and J.W.F. Valle, 'Light stop: MSSM versus R-parity violation', hep-ph/0001033
A search for neutral Higgs bosons has been performed with the OPAL detector at LEP, using approximately 170 pb^{-1} of e+e- collision data collected at sqrt{s} ~ 189 GeV. Searches have been performed for the Standard Model (SM) process e+e- -> HZ and the MSSM processes e+e- -> hZ, Ah. The searches are sensitive to the bb and tautau decay modes of the Higgs bosons, and also to the MSSM decay mode h->AA. OPAL search results at lower centre-of-mass energies have been incorporated in the limits we set, which are valid at the 95 % confidence level. For the SM Higgs boson, we obtain a lower mass bound of 91.0 GeV. In the MSSM, our limits are mh>74.8 GeV and mA>76.5 GeV, assuming tan(beta)>1, that the mixing of the scalar top quarks is either zero or maximal, and that the soft SUSY-breaking masses are 1 TeV. For the case of zero scalar top mixing, we exclude values of tan(beta) between 0.72 and 2.19.
Authors:The OPAL collaboration
Proposed speaker:
Contact person:David J Miller
(CERN),
dave.miller@cern.ch
Sessions: PA-11 Search for New Particles and New Phenomena / PL-07a Search for New Particles and New Phenomena (Results from e+e- Colliders)
Supporting papers: CERN-EP/99-096, Eur.Phys. J. C12 (2000) 567-586 =http://opal.web.cern.ch/Opal/pubs/paper/html/pr285.html
Notes:
A search is described for the generic process e+e- -> XY, where X is a neutral heavy scalar boson decaying into a pair of photons, and Y is a neutral heavy boson (scalar or vector) decaying into a fermion pair. The search is motivated mainly by the cases where either X, or both X and Y, are Higgs bosons. In particular, we investigate the case where X is the Standard Model Higgs boson and Y the Z0 boson. Other models with enhanced Higgs boson decay couplings to photon pairs are also considered. The present search combines the data set collected by the OPAL collaboration at 189 GeV collider energy, having an integrated luminosity of 182.6 pb^-1, with data samples collected at lower energies. The search results have been used to put 95 % confidence level bounds, as functions of the mass MX, on the product of the cross-section and the relevant branching ratios, both in a model independent manner and for the particular models considered.
Authors:The OPAL collaboration
Proposed speaker:
Contact person:David J Miller
(CERN),
dave.miller@cern.ch
Sessions: PA-11 Search for New Particles and New Phenomena / PL-07a Search for New Particles and New Phenomena (Results from e+e- Colliders)
Supporting papers: CERN-EP/99-084, Phys. Lett. B464 (1999) 311-322 =http://opal.web.cern.ch/Opal/pubs/paper/html/pr281.html
Notes:
The data collected by the OPAL experiment at sqrt(s)=183 GeV were used to search for Higgs bosons which are predicted by the Standard Model and various extensions, such as general models with two Higgs field doublets and the Minimal Supersymmetric Standard Model (MSSM). The data correspond to an integrated luminosity of approximately 54~\pb. None of the searches for neutral and charged Higgs bosons have revealed an excess of events beyond the expected background. This negative outcome, in combination with similar results from searches at lower energies, leads to new limits for the Higgs boson masses and other model parameters. In particular, the 95 % confidence level lower limit for the mass of the Standard Model Higgs boson is 88.3 GeV. Charged Higgs bosons can be excluded for masses up to 59.5 GeV. In the MSSM, mh > 70.5 GeV and mA > 72.0 GeV are obtained for tan{beta}>1, no and maximal scalar top mixing and soft SUSY-breaking masses of 1 TeV. The range 0.8 < tan(beta) < 1.9 is excluded for minimal scalar top mixing and m_top < 175 GeV. More general scans of the MSSM parameter space are also considered.
Authors:The OPAL collaboration
Proposed speaker:
Contact person:David J Miller
(CERN),
dave.miller@cern.ch
Sessions: PA-11 Search for New Particles and New Phenomena / PL-07a Search for New Particles and New Phenomena (Results from e+e- Colliders)
Supporting papers: CERN-EP/98-173, Eur. Phys. J. C7 (1999) 407-435 =http://opal.web.cern.ch/Opal/pubs/paper/html/pr261.html
Notes:
Photonic events with missing energy have been observed in 189 GeV e+e- collisions using the OPAL detector at LEP. Results are presented for single-photon and acoplanar-photons event topologies. Cross-section measurements are performed and the number of light neutrino species is measured. Upper limits on cross-section times branching ratios for the class of new physics models e+ e- -> XX or XY are derived for stable and invisible Y. Macroscopic decay lengths are considered in XX production when Y is nearly massless. Constraints are placed on superlight gravitino pair production as well as graviton-photon production in models with additional space dimensions.
Authors:The OPAL collaboration
Proposed speaker:
Contact person:David J Miller
(CERN),
dave.miller@cern.ch
Sessions: PA-11 Search for New Particles and New Phenomena / PL-07a Search for New Particles and New Phenomena (Results from e+e- Colliders)
Supporting papers: OPAL preprint PR306, submitted to Eur. Phys. J. C =http://opal.web.cern.ch/Opal/pubs/paper/html/pr306.html
Notes:
A selection of di-lepton events with significant missing transverse momentum has been performed using a total data sample of 237.4 inverse pico-barns at e+e- centre-of-mass energies of 183 GeV and 189 GeV. The observed numbers of events --- 78 at 183 GeV and 301 at 189 GeV --- are consistent with the numbers expected from Standard Model processes, which arise predominantly from W-pair production with each W decaying leptonically. This topology is also an experimental signature for the pair production of new particles that decay to a charged lepton accompanied by one or more invisible particles. Discrimination techniques are described that optimise the sensitivity to particular new physics channels. No evidence for new phenomena is apparent and model independent limits are presented on the production cross-section times branching ratio squared for sleptons and for leptonically decaying charginos and charged Higgs.
Authors:The OPAL collaboration
Proposed speaker:
Contact person:David J Miller
(CERN),
dave.miller@cern.ch
Sessions: PA-11 Search for New Particles and New Phenomena / PL-07a Search for New Particles and New Phenomena (Results from e+e- Colliders)
Supporting papers: CERN-EP/99-122, accepted by Eur. Phys. J. C =http://opal.web.cern.ch/Opal/pubs/paper/html/pr290.html
Notes:
Data from HERA, LEP, Tevatron and low energy experiments are used to constrain scalar and vector leptoquark couplings. For very high leptoquark masses the contact-interaction approximation is used. For low masses the coupling limits are studied as a function of the mass. Some models describe existing experimental data much better than the Standard Model. For S_1 and V~_o models this corresponds to more than a 3 sigma effect. An allowed region in the l-M plane is calculated. The leptoquark signal is results from the new APV measurements in cesium, but is also supported by LEP2 and HERA results.
Authors:A.F.Zarnecki
Proposed speaker: A.F.Zarnecki
Contact person:Aleksander F Zarnecki
(Warsaw University),
zarnecki@fuw.edu.pl
Sessions: PA-11 Search for New Particles and New Phenomena / PL-07b Search for New Particles and New Phenomena (Results from Hadron Colliders)
Supporting papers: hep-ph/0003271 (results) Eur. Phys. J. C 11 (1999) 3, 539-557 (method; also available as hep-ph/9904334)
Notes:New version of the paper (including NLO QCD corrections for HERA and some new data) will be submitted in May.
We have searched for scalar partners of fermions, charginos, neutralinos, single top quark production, heavy long-lived charged particles, anomalous photonic events, and heavy and excited leptons using the OPAL detector at LEP. The analyses use all available data from the OPAL detector including the year 2000 LEP run.
Authors:The OPAL collaboration
Proposed speaker:
Contact person:David J Miller
(CERN),
dave.miller@cern.ch
Sessions: PA-11 Search for New Particles and New Phenomena / PL-07a Search for New Particles and New Phenomena (Results from e+e- Colliders)
Supporting papers: To be submitted to the conference and listed on http://opal.web.cern.ch/Opal/pubs/publications.html
Notes:
Preliminary results of searches for Higgs bosons are described, using data from the OPAL detector including the year 2000 LEP run. Searches have been performed for the Standard Model (SM) process e+e- -> HZ and the Minimal Supersymmetric extension of the Standard Model processes e+e- -> hZ and e+e- -> Ah. The process e+e- -> H+H- predicted by models with two Higgs field doublets has been searched for. We have also searched for the decays of Higgs bosons to invisible particles and to photons (h ->gamma gamma).
Authors:The OPAL collaboration
Proposed speaker:
Contact person:David J Miller
(CERN),
dave.miller@cern.ch
Sessions: PA-11 Search for New Particles and New Phenomena / PL-07a Search for New Particles and New Phenomena (Results from e+e- Colliders)
Supporting papers: To be submitted to the conference and listed on http://opal.web.cern.ch/Opal/pubs/publications.html
Notes:
We have searched for scalar partners of fermions, charginos, neutralinos, heavy long-lived charged particles, anomalous photonic events, and heavy and excited leptons. The analyses combines up to 200 pb^-1 of data collected with the OPAL detector at 192-202 GeV.
Authors:The OPAL collaboration
Proposed speaker:
Contact person:David J Miller
(CERN),
dave.miller@cern.ch
Sessions: PA-11 Search for New Particles and New Phenomena / PL-07a Search for New Particles and New Phenomena (Results from e+e- Colliders)
Supporting papers: OPAL Physics Note PN418 =http://opal.web.cern.ch/Opal/pubs/physnote/html/pn418.html
Notes:
Preliminary results of searches for Higgs bosons are described based on ~200 pb^-1 of data collected at 192-202 GeV with the OPAL detector at LEP. Searches have been performed for the Standard Model (SM) process e+e- -> HZ and the Minimal Supersymmetric extension of the Standard Model processes e+e- -> hZ and e+e- -> Ah. The process e+e- -> H+H- predicted by models with two Higgs field doublets has been searched for. We have also searched for the decays of Higgs bosons to invisible particles and to photons (h ->gamma gamma).
Authors:The OPAL collaboration
Proposed speaker:
Contact person:David J Miller
(CERN),
dave.miller@cern.ch
Sessions: PA-11 Search for New Particles and New Phenomena / PL-07a Search for New Particles and New Phenomena (Results from e+e- Colliders)
Supporting papers: OPAL Physics Note PN421 =http://opal.web.cern.ch/Opal/pubs/physnote/html/pn421.html
Notes:
A search for the supersymmetric partner of the goldstino, the sgoldstino S, at LEP2 is presented. The production S$\gamma$ followed by S decay into two gluons and into two photons was studied at 189-202 LEP centre-of-mass energies. No evidence for the S production was found and limits on the S mass in correspondence to different theory parameters are given.
Authors:DELPHI Collaboration
Proposed speaker:
Contact person:Clara Matteuzzi
(University of Milano),
Clara.Matteuzzi@cern.ch
Sessions: PA-11 Search for New Particles and New Phenomena / PL-07a Search for New Particles and New Phenomena (Results from e+e- Colliders)
Supporting papers:
Notes:
An update of the searches for charginos, neutralinos and gravitinos is presented, based on 227 $pb^{-1}$ of data collected by DELPHI in 1999, at centre-of-mass energies from 192 to 202 GeV. No evidence for a signal was found. Lower limits on chargino mass are derived. The ($\mu,M_2$) MSSM domain excluded by combining the chargino searches with neutralino searches at the Z resonance is used to set a lower limit on the mass of the lightest neutralino for high $m_0$ and tan(Beta) > 1. Upper limits on the neutralino production cross section times branching fraction are derived.
Authors:DELPHI Collaboration
Proposed speaker:
Contact person:Clara Matteuzzi
(University of Milano),
Clara.Matteuzzi@cern.ch
Sessions: PA-11 Search for New Particles and New Phenomena / PL-07a Search for New Particles and New Phenomena (Results from e+e- Colliders)
Supporting papers:
Notes:
Results of the search for singly produced excited leptons with the DELPHI detector at LEP are reported. The data analysed correspond to an integrated luminosity of about 230 pb$^{-1}$, collected in 1999 at e+e- centre-of-mass energies ranging from 192 to 202 GeV. Upper limits on the ratio of the coupling of the excited lepton to its mass (lambda / m_l*) as a function of the mass are given.
Authors:DELPHI Collaboration
Proposed speaker:
Contact person:Clara Matteuzzi
(University of Milano),
Clara.Matteuzzi@cern.ch
Sessions: PA-11 Search for New Particles and New Phenomena / PL-07a Search for New Particles and New Phenomena (Results from e+e- Colliders)
Supporting papers:
Notes:
Final states with isolated photons were explored in order to search for Higgs bosons with non fermionic couplings. The data collected by the DELPHI detector at centre-of-mass energies ranging from 192 GeV to 202 GeV corresponding to a total integrated luminosity of 230 pb$^{-1}$ were analysed. No evidence for a signal was found and confidence limits were derived in the framework of possible extensions of the SM Higgs sector.
Authors:DELPHI Collaboration
Proposed speaker:
Contact person:Clara Matteuzzi
(University of Milano),
Clara.Matteuzzi@cern.ch
Sessions: PA-11 Search for New Particles and New Phenomena / PL-07a Search for New Particles and New Phenomena (Results from e+e- Colliders)
Supporting papers:
Notes:
Technicolor represents a viable alternative to the Higgs mechanism to generate the W/Z masses. While the minimal version of the model seems rejected by the LEP 1 precision measurements, one cannot exclude more elaborated schemes like "walking-technicolor" which predict a rich spectrum of mesons which could be directly/indirectly observed at LEP 2. This note presents the preliminary results of the search for technicolor with the DELPHI detector at LEP based on ${W_L}^+\{pi_T}^-$ and ${\pi_T}^+{\pi_T}^-$ final states.
Authors:DELPHI Collaboration
Proposed speaker:
Contact person:Clara Matteuzzi
(University of Milano),
Clara.Matteuzzi@cern.ch
Sessions: PA-11 Search for New Particles and New Phenomena / PL-07a Search for New Particles and New Phenomena (Results from e+e- Colliders)
Supporting papers:
Notes:
A search for charginos and neutralinos, predicted by supersymmetric theories, is performed using a data sample of 57 inverse pico-barns taken at a centre-of-mass energy of 181-184 GeV with the OPAL detector at LEP. No evidence for chargino or neutralino production is found. Upper limits on chargino and neutralino pair production cross-sections are obtained as a function of the chargino mass, the lightest neutralino mass and the second lightest neutralino mass. Limits on the chargino and neutralino masses are inferred within the Constrained Minimal Supersymmetric Standard Model framework.
Authors:The OPAL collaboration
Proposed speaker:
Contact person:David J Miller
(CERN),
dave.miller@cern.ch
Sessions: PA-11 Search for New Particles and New Phenomena / PL-07a Search for New Particles and New Phenomena (Results from e+e- Colliders)
Supporting papers: CERN-EP/98-136, Eur. Phys. J. C8 (1999) 255-272 =http://opal.web.cern.ch/Opal/pubs/paper/html/pr256.html
Notes:
Photonic events with large missing energy have been observed in e+e- collisions at a centre-of-mass energy of 130, 136 and 183 GeV using the OPAL detector at LEP. Results are presented for event topologies consistent with a single photon or with an acoplanar photon pair. Cross-section measurements are performed within the kinematic acceptance of each selection. These results are compared with the expectations from the Standard Model. No evidence is observed for new physics contributions to these final states. Upper limits on the cross-sections for the production of XY and XX final states, followed by the decay X to Y gamma, are derived for the case of stable and invisible Y. These limits apply to single and pair production of excited neutrinos, to neutralino production and to supersymmetric models with a light gravitino.
Authors:The OPAL collaboration
Proposed speaker:
Contact person:David J Miller
(CERN),
dave.miller@cern.ch
Sessions: PA-11 Search for New Particles and New Phenomena / PL-07a Search for New Particles and New Phenomena (Results from e+e- Colliders)
Supporting papers: CERN-EP/98-143, Eur. Phys. J. C8 (1999) 23-40 =http://opal.web.cern.ch/Opal/pubs/paper/html/pr258.html
Notes:
A search has been performed for pair-production of stable and long-lived massive particles with charge |Q/e|=1 or 2/3. No evidence for the production of such particles was observed. The cross-section upper limits vary between 0.015 and 0.25 pb for particles of charge +-1. Within the MSSM, lower mass limits on the the right- (left-) handed smuons and staus, of 88.0 GeV (90.0 GeV), have been obtained. Heavy long-lived charged leptons and long-lived charginos with masses smaller than 93.5 GeV are excluded. For particles with charge +-2/3, the production cross-section upper limits vary between 0.015 and 0.07 pb.
Authors:The OPAL collaboration
Proposed speaker:
Contact person:David J Miller
(CERN),
dave.miller@cern.ch
Sessions: PA-11 Search for New Particles and New Phenomena / PL-07a Search for New Particles and New Phenomena (Results from e+e- Colliders)
Supporting papers: OPAL Physics Note PN395 =http://opal.web.cern.ch/Opal/pubs/physnote/html/pn395.html
Notes:
Using data collected with the OPAL detector at LEP, we have searched for the decays of Z to a proton plus an electron or protron plus a muon. These would violate the conservation of the baryon-number B, lepton-number L and the fermion-number n = (B+L). No evidence for such decays has been found, and the 95% confidence level upper limits on the respective partial widths are found to be 4.6 and 4.4 keV.
Authors:The OPAL collaboration
Proposed speaker:
Contact person:David J Miller
(CERN),
dave.miller@cern.ch
Sessions: PA-11 Search for New Particles and New Phenomena / PL-07a Search for New Particles and New Phenomena (Results from e+e- Colliders)
Supporting papers: CERN-EP/98-194, Phys. Lett. B447 (1999) 157-166 =http://opal.web.cern.ch/Opal/pubs/paper/html/pr263.html
Notes:
Data from HERA, LEP, Tevatron and low energy experiments are used to constrain scalar and vector leptoquark couplings. For very high leptoquark masses the contact-interaction approximation is used. For low masses the coupling limits are studied as a function of the mass. Some models describe existing experimental data much better than the Standard Model. For S_1 and V~_o models this corresponds to more than a 3 sigma effect. An allowed region in the l-M plane is calculated. The leptoquark signal is results from the new APV measurements in cesium, but is also supported by LEP2 and HERA results.
Authors:A.F.Zarnecki
Proposed speaker: A.F.Zarnecki
Contact person:Aleksander F Zarnecki
(Warsaw University),
zarnecki@fuw.edu.pl
Sessions: PA-11 Search for New Particles and New Phenomena / PL-07a Search for New Particles and New Phenomena (Results from e+e- Colliders)
Supporting papers: hep-ph/0003271 (results) Eur. Phys. J. C 11 (1999) 3, 539-557 (method; also available as hep-ph/9904334)
Notes:New version of the paper (including NLO QCD corrections for HERA and some new data) will be submitted in May. DUPLICATED COPY OF #167 for PL-07a speaker. (4/19/00 TY)
Searches have been performed in the data collected by the OPAL detector at LEP taken with centre-of-mass energies up to 202 GeV for the Standard Model (SM) process e+e- -> HZ and the Minimal Supersymmetric extension of the Standard Model (MSSM) processes e+e- -> hZ and e+e- -> Ah. In each case, the analyses are sensitive to Higgs bosons decaying into bb or tautau. The results are used to set a lower mass limit of the SM Higgs. The MSSM parameter space has been scanned, and limits on mh, mA and tan(beta) are derived.
Authors:The OPAL collaboration
Proposed speaker:
Contact person:David J Miller
(CERN),
dave.miller@cern.ch
Sessions: PA-11 Search for New Particles and New Phenomena / PL-07a Search for New Particles and New Phenomena (Results from e+e- Colliders)
Supporting papers: To be submitted to the conference and listed on http://opal.web.cern.ch/Opal/pubs/publications.html Preliminary results available as OPAL Physics Note PN426 at http://opal.web.cern.ch/Opal/pubs/physnote/html/pn426.html
Notes:
Searches have been made for the neutral Higgs bosons predicted by models with two Higgs field doublets (2HDM). Type II 2HDM models are considered, and e+e- collision data from the OPAL detector at LEP with centre-of-mass energies upto 189 GeV have been used. The results of searches for SM or MSSM Higgs bosons production have been combined with the results from searches which extend the sensitivity to general hadronic decays of the Higgs bosons. The analyses exclude large areas of the parameter space of the 2HDM.
Authors:The OPAL collaboration
Proposed speaker:
Contact person:David J Miller
(CERN),
dave.miller@cern.ch
Sessions: PA-11 Search for New Particles and New Phenomena / PL-07a Search for New Particles and New Phenomena (Results from e+e- Colliders)
Supporting papers: To be submitted to the conference and listed on http://opal.web.cern.ch/Opal/pubs/publications.html Preliminary results available as OPAL Physics Note PN416 at http://opal.web.cern.ch/Opal/pubs/physnote/html/pn416.html
Notes:
Using 175 pb^-1 of data recorded with the OPAL detector at 189 GeV center of mass energy, we have conducted a search for Model I charged Higgs production, which assumes that all of the fermions couple to the same Higgs doublet, making H^+ --> W^* A^0 the dominant decay mode at high tan(beta). We have performed a new multichannel analysis to identify candidates for such W^* mediated three-body decays and combined the results with that of a previous search for H^+ --> tau nu and H^+ --> q qbar in order to scan the Model I parameter space as a function of tan(beta) and the H^+ and A^0 masses for evidence of charged Higgs production.
Authors:The OPAL collaboration
Proposed speaker:
Contact person:David J Miller
(CERN),
dave.miller@cern.ch
Sessions: PA-11 Search for New Particles and New Phenomena / PL-07a Search for New Particles and New Phenomena (Results from e+e- Colliders)
Supporting papers: To be submitted to the conference and listed on http://opal.web.cern.ch/Opal/pubs/publications.html
Notes:5/10/00 TY- The text of abstract was replaced based on the request by D.Miller.
Searches for charged Higgs bosons are described using data from e+e- collisions collected by the OPAL detector at LEP taken with centre-of-mass energies up to 202 GeV. The pair production process, e+e- -> H+H-, with charged Higgs decaying to quark pairs or tau and neutrino has been searched for. The limit on the mass of the charged Higgs boson is given as a function of the branching ratio of the process H+ -> tau+ nu_tau.
Authors:The OPAL collaboration
Proposed speaker:
Contact person:David J Miller
(CERN),
dave.miller@cern.ch
Sessions: PA-11 Search for New Particles and New Phenomena / PL-07a Search for New Particles and New Phenomena (Results from e+e- Colliders)
Supporting papers: To be submitted to the conference and listed on http://opal.web.cern.ch/Opal/pubs/publications.html
Notes:
A search for resonant production of high mass photon pairs associated with a leptonic or hadronic system has been performed using data from e+e- collisions collected by the OPAL detector at LEP taken with centre-of-mass energies up to 202 GeV. The observed candidates are used to place limits on Br(H0 -> gamma gamma) assuming the Standard Model production rate for H0Z0. If the couplings of the Higgs boson to fermions are assumed to be zero, then the lower mass limit of 97.8 GeV is obtained.
Authors:The OPAL collaboration
Proposed speaker:
Contact person:David J Miller
(CERN),
dave.miller@cern.ch
Sessions: PA-11 Search for New Particles and New Phenomena / PL-07a Search for New Particles and New Phenomena (Results from e+e- Colliders)
Supporting papers: To be submitted to the conference and listed on http://opal.web.cern.ch/Opal/pubs/publications.html
Notes:
A search for invisibly decaying Higgs boson produced in association with a Z0 boson has been performed using data taken with the OPAL detector at LEP at the centre-of-mass energies up to 202 GeV. The search is sensitive to the MSSM Higgs decay to invisible particles such as LSP neutralinos. The upper limit is placed on Br(h -> invisible}) assuming the Standard Model production rate.
Authors:The OPAL collaboration
Proposed speaker:
Contact person:David J Miller
(CERN),
dave.miller@cern.ch
Sessions: PA-11 Search for New Particles and New Phenomena / PL-07a Search for New Particles and New Phenomena (Results from e+e- Colliders)
Supporting papers: To be submitted to the conference and listed on http://opal.web.cern.ch/Opal/pubs/publications.html
Notes:
With certain choices of the parameters in models such as the two Higgs field doublets models (2HDM), the decay of the CP even Higgs boson into bb and tau+tau-. which are dominating in the Standard Model, are suppressed. Searches have been performed using the data taken by the OPAL detector at LEP for the Higgsstrahlung process assuming hadronic decays of the Higgs but not assuming the flavour composition. The results are used to set limit on the cross-section of the Higgsstahlung process as functions of the Higgs boson mass, assuming either a total hadronic branching ratio of unity or that predicted by Type II 2HDM.
Authors:The OPAL collaboration
Proposed speaker:
Contact person:David J Miller
(CERN),
dave.miller@cern.ch
Sessions: PA-11 Search for New Particles and New Phenomena / PL-07a Search for New Particles and New Phenomena (Results from e+e- Colliders)
Supporting papers: To be submitted to the conference and listed on http://opal.web.cern.ch/Opal/pubs/publications.html Preliminary results available as OPAL Physics Note PN419 at http://opal.web.cern.ch/Opal/pubs/physnote/html/pn419.html
Notes:
A search has been performed for a light Higgs boson in a Two-Higgs-Doublet Model (2HDM) produced in e+e- collisions at 91 GeV via the process e+e- -> bbA0/h0 -> bb tau+tau-. The analysis is sensitive for A0 and h0 in the mass range of 4 to 10 GeV. A selection is applied to identify candidates using the data collected between 1991 and 1995 at the Z0-peak. The number of observed events is in good agreement with the number of expected background. The results are translated into a CP conserving non supersymmetric type II 2HDM and limits are presented on xi_A}=tan(beta) and xi_h=Cos(alpha)/sin(beta) for the production of A0 and h0.
Authors:The OPAL collaboration
Proposed speaker:
Contact person:David J Miller
(CERN),
dave.miller@cern.ch
Sessions: PA-11 Search for New Particles and New Phenomena / PL-07a Search for New Particles and New Phenomena (Results from e+e- Colliders)
Supporting papers: To be submitted to the conference and listed on http://opal.web.cern.ch/Opal/pubs/publications.html
Notes:
A search for charginos and neutralinos, predicted by supersymmetric theories, is performed using a data sample of 214 inverse pico-barns taken at a centre-of-mass energy of 192-202 GeV with the OPAL detector at LEP. A likelihood technique is used to optimize the analysis sensitivity, using an interpolation technique to construct signal kinematic distributions at arbitrary chargino and neutralino masses. Upper limits on chargino and neutralino pair production cross-sections are obtained as a function of the chargino mass, the lightest neutralino mass and the second lightest neutralino mass. Limits on the chargino and neutralino masses are inferred within the Constrained Minimal Supersymmetric Standard Model framework.
Authors:The OPAL collaboration
Proposed speaker:
Contact person:David J Miller
(CERN),
dave.miller@cern.ch
Sessions: PA-11 Search for New Particles and New Phenomena / PL-07a Search for New Particles and New Phenomena (Results from e+e- Colliders)
Supporting papers: To be submitted to the conference and listed on http://opal.web.cern.ch/Opal/pubs/publications.html
Notes:
Searches for pair-produced gauginos and scalar leptons with decays violating R-parity with lambda, lambda prime and lambda double prime couplings have been performed using a data sample corresponding to an integrated luminosity of about 175 pb^-1 collected with the OPAL detector at a centre-of-mass energy around 189 GeV. The searches have been performed under the assumptions that the lightest supersymmetric particle promptly decays and that only one R-parity violating coupling is dominant for each of the decay modes considered.
Authors:The OPAL collaboration
Proposed speaker:
Contact person:David J Miller
(CERN),
dave.miller@cern.ch
Sessions: PA-11 Search for New Particles and New Phenomena / PL-07a Search for New Particles and New Phenomena (Results from e+e- Colliders)
Supporting papers: To be submitted to the conference and listed on http://opal.web.cern.ch/Opal/pubs/publications.html
Notes:
Searches for pair-produced gauginos and scalar leptons with decays violating R-parity with lambda, lambda prime and lambda double prime couplings have been performed using a data sample corresponding to an integrated luminosity of about 400 pb^-1 collected with the OPAL detector at a centre-of-mass energy up to 202 GeV. The searches have been performed under the assumptions that the lightest supersymmetric particle promptly decays and that only one R-parity violating coupling is dominant for each of the decay modes considered.
Authors:The OPAL collaboration
Proposed speaker:
Contact person:David J Miller
(CERN),
dave.miller@cern.ch
Sessions: PA-11 Search for New Particles and New Phenomena / PL-07a Search for New Particles and New Phenomena (Results from e+e- Colliders)
Supporting papers: To be submitted to the conference and listed on http://opal.web.cern.ch/Opal/pubs/publications.html
Notes:
Searches for final states expected in models with light gravitinos have been performed, including experimental topologies with multi-leptons with missing energy, leptons and photons with missing energy, and jets and photons with missing energy. No excess over the expectations from the Standard Model has been observed. Limits are placed on production cross-sections in the different experimental topologies. Additionally, combining with searches for the anomalous production of lepton and photon pairs with missing energy, results are interpreted in the context of minimal models of gauge mediated SUSY breaking.
Authors:The OPAL collaboration
Proposed speaker:
Contact person:David J Miller
(CERN),
dave.miller@cern.ch
Sessions: PA-11 Search for New Particles and New Phenomena / PL-07a Search for New Particles and New Phenomena (Results from e+e- Colliders)
Supporting papers: To be submitted to the conference and listed on http://opal.web.cern.ch/Opal/pubs/publications.html
Notes:
Searches for final states expected in models in which particles decay with measurable lifetime into light gravitinos have been performed, including experimental topologies of tracks with large impact parameters, kinked tracks, and photons which do not point to the interaction point. No excess over the expectations from the Standard Model has been observed. Limits are placed on production cross-sections in the different experimental topologies.
Authors:The OPAL collaboration
Proposed speaker:
Contact person:David J Miller
(CERN),
dave.miller@cern.ch
Sessions: PA-11 Search for New Particles and New Phenomena / PL-07a Search for New Particles and New Phenomena (Results from e+e- Colliders)
Supporting papers: To be submitted to the conference and listed on http://opal.web.cern.ch/Opal/pubs/publications.html
Notes:
A search for pair production of Charginos nearly mass degenerate with the lightest Neutralino in e+e- collsioins was performed. The data were collected at centre-of-mass energies between 189 and 202 GeV using the OPAL detector at LEP. Events with high-energetic photons from initial state radiation were selected reducing the dominant two-photon background to a negligible level. The search is sensitive to mass differences ranging from a few hundred MeV to 5 GeV. No significant excess with respect to the Standard Model background was observed. Upper limits on the cross-section for chargino pair-production are set and lower limits on the chargino mass are derived for several models.
Authors:The OPAL collaboration
Proposed speaker:
Contact person:David J Miller
(CERN),
dave.miller@cern.ch
Sessions: PA-11 Search for New Particles and New Phenomena / PL-07a Search for New Particles and New Phenomena (Results from e+e- Colliders)
Supporting papers: To be submitted to the conference and listed on http://opal.web.cern.ch/Opal/pubs/publications.html
Notes:
Searches for singly and pair produced charged excited leptons with photonic decays in e+e- collisions have been performed using the OPAL detector at LEP. The data analysed correspond to an integrated luminosity of about 400 inverse pico-barns at a centre-of-mass energy of 189 - 202 GeV. Lower limits on the masses of excited leptons are derived from the pair production searches. Upper limits are determined for the ratio of the coupling to the compositeness scale from the single production searches, for masses up to the kinematic limit.
Authors:The OPAL collaboration
Proposed speaker:
Contact person:David J Miller
(CERN),
dave.miller@cern.ch
Sessions: PA-11 Search for New Particles and New Phenomena / PL-07a Search for New Particles and New Phenomena (Results from e+e- Colliders)
Supporting papers: To be submitted to the conference and listed on http://opal.web.cern.ch/Opal/pubs/publications.html
Notes:
Leptoquarks (LQ) are bosonic particles predicted in many extensions of the Standard Model. Within the usual models they could be pair-produced in the electron-positron collisions at LEP. A search for events with LQ pair-production has been performed using the samples of e+e- interactions events collected by the OPAL detector at centre-of-mass energies from 189 - 202 GeV. Lower mass limits are derived as a function of the different LQ electroweak quantum numbers and of the decay branching ratio into a charged lepton and a quark, under the simplifying assumption of coupling within a single generation of leptons.
Authors:The OPAL collaboration
Proposed speaker:
Contact person:David J Miller
(CERN),
dave.miller@cern.ch
Sessions: PA-11 Search for New Particles and New Phenomena / PL-07a Search for New Particles and New Phenomena (Results from e+e- Colliders)
Supporting papers: To be submitted to the conference and listed on http://opal.web.cern.ch/Opal/pubs/publications.html
Notes:
A search for first generation scalar and vector leptoquarks (LQ) as well as for squarks in R-parity violating SUSY models has been performed using the full sample of e+e- collisions collected by the OPAL detector at LEP at centre-of-mass energies of 189 GeV. The number of selected events found in the two decay channels are in agreement with the expectations from Standard Model processes. This result allows to set lower limits at the 95 % confidence level on the mass of first generation scalar (vector) leptoquarks and of squarks in R-parity violating SUSY models.
Authors:The OPAL collaboration
Proposed speaker:
Contact person:David J Miller
(CERN),
dave.miller@cern.ch
Sessions: PA-11 Search for New Particles and New Phenomena / PL-07a Search for New Particles and New Phenomena (Results from e+e- Colliders)
Supporting papers: To be submitted to the conference and listed on http://opal.web.cern.ch/Opal/pubs/publications.html
Notes:
Photonic events with missing energy have been observed in 192-206 GeV e+e- collisions using the OPAL detector at LEP. Results are presented for single-photon and acoplanar-photons event topologies. Cross-section measurements are performed and the number of light neutrino species is measured. Upper limits on cross-section times branching ratios for the class of new physics models e+ e- -> XX or XY are derived for stable and invisible Y. Additional results are given for certain specific new physics models.
Authors:The OPAL collaboration
Proposed speaker:
Contact person:David J Miller
(CERN),
dave.miller@cern.ch
Sessions: PA-11 Search for New Particles and New Phenomena / PL-07a Search for New Particles and New Phenomena (Results from e+e- Colliders)
Supporting papers: To be submitted to the conference and listed on http://opal.web.cern.ch/Opal/pubs/publications.html
Notes:
A selection of di-lepton events with significant missing transverse momentum has been performed using a total data sample of 460 inverse pico-barns at e+e- centre-of-mass energies of 183 to 202 GeV. In addition, events with a single charged lepton and missing energy are selecte Cross-section measurements for each di-lepton final state and single lepton final state are presented and compared with Standard Model predictions arising predominantly from W-pair production and single W production with the W's decaying leptonically. These topologies are used to search for new particle production and results of the searches for selectron, smuon and stau pairs, leptonically decaying charginos and charged Higgs are presented.
Authors:The OPAL collaboration
Proposed speaker:
Contact person:David J Miller
(CERN),
dave.miller@cern.ch
Sessions: PA-11 Search for New Particles and New Phenomena / PL-07a Search for New Particles and New Phenomena (Results from e+e- Colliders)
Supporting papers: To be submitted to the conference and listed on http://opal.web.cern.ch/Opal/pubs/publications.html
Notes:
A search has been performed for pair-production of stable and long-lived massive particles with charge |Q/e|=1 or 2/3. No evidence for the production of such particles was observed. The cross-section upper limits vary between 0.01 and 0.05 pb for particles of charge +-1. Within the MSSM, lower mass limits on the the right- (left-) handed smuons and staus, of 94.0 GeV (95.0 GeV), have been obtained. Heavy long-lived charged leptons and long-lived charginos with masses smaller than 99.5 GeV are excluded. For particles with charge +-2/3, the production cross-section upper limits vary between 0.01 and 0.06 pb.
Authors:The OPAL collaboration
Proposed speaker:
Contact person:David J Miller
(CERN),
dave.miller@cern.ch
Sessions: PA-11 Search for New Particles and New Phenomena / PL-07a Search for New Particles and New Phenomena (Results from e+e- Colliders)
Supporting papers: To be submitted to the conference and listed on http://opal.web.cern.ch/Opal/pubs/publications.html
Notes:
The high luminosity delivered by LEP after the increase of the electron-positron collison energy means that LEP2 is now providing substantial data samples with which to make searches for new phenomena. Based on the analysis of about 175 inverse picobarns of data recorded at a centre-of-mass energy of 189 GeV with the OPAL detector, a search for single top-quark production via flavour changing neutral current has been performed. Limits for FCNC processes predicted by extensions of the Standard Model are set. The search is sensitive to both the hadronic and leptonic decay channels of the W boson associated with the decay of the top quark.
Authors:The OPAL collaboration
Proposed speaker:
Contact person:David J Miller
(CERN),
dave.miller@cern.ch
Sessions: PA-11 Search for New Particles and New Phenomena / PL-07a Search for New Particles and New Phenomena (Results from e+e- Colliders)
Supporting papers: OPAL Physics Note PN429 http://opal.web.cern.ch/Opal/pubs/physnote/html/pn429.html
Notes:
The high luminosity delivered by LEP after the increase of the electron-positron collison energy means that LEP2 is now providing substantial data samples with which to make searches for new phenomena. Based on the analysis of several hundred inverse picobarns of data recorded at centre-of-mass energies between 189 GeV and 204 GeV with the OPAL detector, a search for single top-quark production via flavour changing neutral current has been performed. Limits for FCNC processes predicted by extensions of the Standard Model are set. The search is sensitive to both the hadronic and leptonic decay channels of the W boson associated with the decay of the top quark.
Authors:The OPAL collaboration
Proposed speaker:
Contact person:David J Miller
(CERN),
dave.miller@cern.ch
Sessions: PA-11 Search for New Particles and New Phenomena / PL-07a Search for New Particles and New Phenomena (Results from e+e- Colliders)
Supporting papers: To be submitted to the conference and listed on http://opal.web.cern.ch/Opal/pubs/publications.html Results up to 189 GeV available as OPAL Physics Note PN429 at http://opal.web.cern.ch/Opal/pubs/physnote/html/pn429.html
Notes:
The OPAL data sets at centre-of-mass energies between 189 GeV and 202 GeV have been searched for evidence of the reaction e +e- -> H++ H--, followed by the decays H++ -> tau++. No evidence for doubly charged higgs production is observed. Monte Carlo simulations show that the detection efficiencies for four tau lepton events from H++ H-- vary from 23% to 30% in the H++ mass range from 45 to 101 GeV A mass limit on the doubly charged Higgs particle has been derived.
Authors:The OPAL collaboration
Proposed speaker:
Contact person:David J Miller
(CERN),
dave.miller@cern.ch
Sessions: PA-11 Search for New Particles and New Phenomena / PL-07a Search for New Particles and New Phenomena (Results from e+e- Colliders)
Supporting papers: To be submitted to the conference and listed on http://opal.web.cern.ch/Opal/pubs/publications.html
Notes:
The data collected at the centre-of-mass energy 188.6 GeV by ALEPH at LEP are analyzed in a search for pair-produced charged Higgs bosons H+ H-. Three analyses are employed to select the tau nu tau nu, tau nu cs and cscs final states. No evidence for a signal is found. Upper limits are set on the production cross section as a function of the branching fraction B(H -> tau nu) and of the mass m_H, in the framework of a two Higgs doublets model and assuming B(H -> tau nu)+B(H -> c s)=1.
Authors:ALEPH collaboration
Proposed speaker:
Contact person:Fabrizio Palla
(CERN),
Fabrizio.Palla@cern.ch
Sessions: PA-11 Search for New Particles and New Phenomena / PL-07a Search for New Particles and New Phenomena (Results from e+e- Colliders)
Supporting papers:
Notes:
A search for neutral Higgs bosons of the Standard Model and the MSSM is performed with the ALEPH detector at LEP centre-of-mass energies from 192 to 202 GeV. Searches are also conducted in the context of an invisibly decaying Higgs boson. No evidence for signal is found. The searches allow lower limits to be set on the Standard Model Higgs boson mass, on the masses of the Higgs bosons h and A for the MSSM benchmark parameter choices, and on the mass of the insivible decaying Higgs boson for a cross section equal to that of the Standard Model.
Authors:ALEPH collaboration
Proposed speaker:
Contact person:Fabrizio Palla
(CERN),
Fabrizio.Palla@cern.ch
Sessions: PA-11 Search for New Particles and New Phenomena / PL-07a Search for New Particles and New Phenomena (Results from e+e- Colliders)
Supporting papers:
Notes:
The data collected at LEP centre-of-mass energies from 192 to 202 GeV by the ALEPH experiment are analyzed in a search for pair-produced charged Higgs bosons. No evidence for a signal is found. Upper limits are set on the production cross section as a function of the branching fraction B(H -> tau nu) and of the mass m_H. In the framework of a two Higgs doublets model and assuming B(H -> tau nu)+B(H -> c s)=1, a lower limit of charged Higgs bosons are set at 95% confidence level independently of the decay mode.
Authors:ALEPH collaboration
Proposed speaker:
Contact person:Fabrizio Palla
(CERN),
Fabrizio.Palla@cern.ch
Sessions: PA-11 Search for New Particles and New Phenomena / PL-07a Search for New Particles and New Phenomena (Results from e+e- Colliders)
Supporting papers:
Notes:
A search for a Higgs boson, decaying into gamma gamma, is performed in the data sample collected at LEP with the ALEPH detector between 1991 and 1999. The search is based on topologies where the Higgs is produced in association with a fermion pair via the Higgs-strahlung process e+e- -> Hffbar. This search results in an upper limit on the product of e+e- -> Hffbar cross section and the H -> gamma gamma branching fraction as a function of the Higgs boson mass.
Authors:ALEPH collaboration
Proposed speaker:
Contact person:Fabrizio Palla
(CERN),
Fabrizio.Palla@cern.ch
Sessions: PA-11 Search for New Particles and New Phenomena / PL-07a Search for New Particles and New Phenomena (Results from e+e- Colliders)
Supporting papers:
Notes:
A preliminary search for Higgs bosons is performed in the data collected by ALEPH in 2000.
Authors:ALEPH collaboration
Proposed speaker:
Contact person:Fabrizio Palla
(CERN),
Fabrizio.Palla@cern.ch
Sessions: PA-11 Search for New Particles and New Phenomena / PL-07a Search for New Particles and New Phenomena (Results from e+e- Colliders)
Supporting papers:
Notes:
Neutral Higgs bosons of the Standard Model and of the MSSM are searched for in the data collected at a centre-of-mass energy of 188.6 GeV by the ALEPH experiment. No evidence for a signal is found. A lower limit of 92.9 Gev/c**2 at 95% confidence level is set on the mass of the Standard Model Higgs boson. In the MSSM, for tanb>0.7 and for benchmark parameter choices, lower limits of 82.5 and 82.6 GeV/c**2 are derived for the masses of the neutral Higgs bosons h and A, respectively. An update of the general MSSM parameter scan is also presented.
Authors:ALEPH collaboration
Proposed speaker:
Contact person:Fabrizio Palla
(CERN),
Fabrizio.Palla@cern.ch
Sessions: PA-11 Search for New Particles and New Phenomena / PL-07a Search for New Particles and New Phenomena (Results from e+e- Colliders)
Supporting papers: CERN-EP 2000-019
Notes:
First results from an experiment (Fermilab E882) searching for magnetically charged particles bound to elements from the CDF and D0 detectors will be reported. The experiment will be described, and limits on magnetic monopole pair production cross sections for magnetic charges 1, 2, 3, and 6 times the Dirac pole strength will be presented. These limits are hundreds of times smaller than those found in previous Fermilab searches. Using simple model assumptions for the photonic production of monopoles, we can convert these cross section limits into mass limits in the hundreds of GeV range.
Authors:G. R. Kalbfleisch, K. A. Milton, M. G. Strauss, L. Gamberg, E. H. Smith, and W. Luo
Proposed speaker: K. A. Milton
Contact person:Kimball A. Milton
(University of Oklahoma),
milton@mail.nhn.ou.edu
Sessions: PA-11 Search for New Particles and New Phenomena / PL-07b Search for New Particles and New Phenomena (Results from Hadron Colliders)
Supporting papers: A paper describing the results to be reported at ICHEP2000 is currently being prepared for submission to Physical Review Letters, and should be available in two weeks time.
Notes:
We measure the mass of the tau lepton to be 1775.1 +/- 1.6(stat.) +/- 1.0(sys.) MeV using tau pairs from Z^0 decays. To test CPT invariance we compare the masses of the positively and negatively charged tau leptons. The relative mass difference is found to be smaller than 3.0 x 10^-3 at the 90% confidence level.
Authors:The OPAL collaboration
Proposed speaker:
Contact person:David J Miller
(CERN),
dave.miller@cern.ch
Sessions: PA-11 Search for New Particles and New Phenomena / PL-07a Search for New Particles and New Phenomena (Results from e+e- Colliders)
Supporting papers: OPAL preprint PR308, submitted to Phys. Letts. B, and at http://opal.web.cern.ch/Opal/pubs/paper/html/pr308.html
Notes:This is a duplicate abstract, and the sessions (PA-11 and PL-7a) are the second choice. The first choice are PA-07 and PL-03.
Searches for non-minimal neutral Higgs bosons over a wide mass range are described. The production channels considered are e+e- -> hZ and hA, with the subsequent decay h -> AA if kinematically allowed. Only decays of the lightest Higgs boson into standard particles are considered, but decays into b quarks are not necessarily assumed. The searches are applied on the recent data collected by Delphi, and interpreted within the frameworks of a general two-doublet model, and of the minimal supersymmetric model extended with a scalar singlet.
Authors:DELPHI Collaboration
Proposed speaker:
Contact person:Clara Matteuzzi
(),
Clara.Matteuzzi@cern.ch
Sessions: PA-11 Search for New Particles and New Phenomena / PL-07a Search for New Particles and New Phenomena (Results from e+e- Colliders)
Supporting papers:
Notes:
Searches for the Higgs bosons of the Standard Model and supersymmetric models have been performed in the data collected by the DELPHI experiment at LEP in 2000 corresponding to centre-of-mass energies above 200 GeV. These results are used, in combination with our results from previous years, to obtain preliminary confidence levels on the existence of an Standard Model Higgs boson with a mass in the range [105-115] GeV/c2. Similarly, preliminary results are given for scans of the MSSM Higgs parameter space, which are sensitive to bosons in the range [85-115] GeV/c2, and for more general Higgs models, including results on the charged Higgs in the range [75-90] GeV/c2.
Authors:DELPHI Collaboration
Proposed speaker:
Contact person:Clara Matteuzzi
(),
Clara.Matteuzzi@cern.ch
Sessions: PA-11 Search for New Particles and New Phenomena / PL-07a Search for New Particles and New Phenomena (Results from e+e- Colliders)
Supporting papers:
Notes:
Searches for HZ production with the Higgs boson decaying into an invisible final state have been performed with the latest data collected by the DELPHI experiment. The hadronic and leptonic final states of the Z boson are analysed and the results are combined with the DELPHI results for the visible Higgs boson decay modes.
Authors:DELPHI Collaboration
Proposed speaker:
Contact person:Clara Matteuzzi
(),
Clara.Matteuzzi@cern.ch
Sessions: PA-11 Search for New Particles and New Phenomena / PL-07a Search for New Particles and New Phenomena (Results from e+e- Colliders)
Supporting papers:
Notes:
Sleptons and neutralinos were searched for in the context of scenarios where the lightest supersymmetric particle is the gravitino. It was assumed that the sleptons are the next-to-lightest supersymmetric particles. Data collected with the DELPHI detector at centre-of-mass energies of 192, 196, 200 and 202 GeV were analysed combining the methods developed in previous searches at lower energies. No evidence for the production of these supersymmetric particles was found. Hence, limits were derived at 95% confidence level.
Authors:DELPHI Collaboration
Proposed speaker:
Contact person:Clara Matteuzzi
(),
Clara.Matteuzzi@cern.ch
Sessions: PA-11 Search for New Particles and New Phenomena / PL-07a Search for New Particles and New Phenomena (Results from e+e- Colliders)
Supporting papers:
Notes:
The excluded tan(beta) range and Higgs boson mass regions in the framework of the Minimal Supersymmetric extension of the Standard Model (MSSM) depend on several parameters. The Higgs boson masses, cross-sections and branching fractions have been determined including two-loop diagrammatic calculations. The limits obtained with a more general scan over the parameter space of the MSSM are compared with those in the so called benchmark scenario. The combination of the searches for Higgs particles in the latest data collected by the DELPHI collaboration at LEP allows to set stringent limits in combination with previous DELPHI results.
Authors:DELPHI Collaboration
Proposed speaker:
Contact person:Clara Matteuzzi
(),
Clara.Matteuzzi@cern.ch
Sessions: PA-11 Search for New Particles and New Phenomena / PL-07a Search for New Particles and New Phenomena (Results from e+e- Colliders)
Supporting papers:
Notes:
The single top production via flavour changing neutral currents in the reactions ee -> t c(u) is searched for in approximately 411 pb-1 of data collected by ALEPH at centre-of-mass energies in the range between 189 and 202 GeV. No deviation from the Standard Model expectation is observed. A 95% CL upper limit on the single top production cross section at Ecm=202 GeV is derived. A model dependent limit on the flavour-changing couplings kZ and kg is obtained by combining all centre-of-mass energies.
Authors:ALEPH collaboration
Proposed speaker:
Contact person:Fabrizio Palla
(CERN),
Fabrizio.Palla@cern.ch
Sessions: PA-11 Search for New Particles and New Phenomena / PL-07a Search for New Particles and New Phenomena (Results from e+e- Colliders)
Supporting papers:
Notes:
We consider the reaction l+ l- -> n b-jets + light jets in lepton colliders for which we propose a useful approximately conserved quantum number b_P=(-1)^n that we call b-Parity. We make the observation that Standard Model processes have even b-Parity to a high accuracy since odd b-Parity signals are necessarily CKM suppressed. In contrast new flavor physics can produce b_P=-1 signals whose only significant SM background is due to b-jet misidentification. Despite this reducible bacground we show that b-jet counting, which relies solely on b-tagging, becomes a simple and sensitive probe of new flavor physics
Authors:Jose Wudka and Shaouly Bar-Shalom
Proposed speaker: Jose Wudka
Contact person:Jose Wudka
(Unviesity of Californai, Riverside),
jose.wudka@ucr.edu
Sessions: PA-11 Search for New Particles and New Phenomena /
Supporting papers: FLAVOR CHANGING SINGLE TOP QUARK PRODUCTION CHANNELS AT E+ E- COLLIDERS IN THE EFFECTIVE LAGRANGIAN DESCRIPTION. S. Bar-Shalom, J. Wudka Phys.Rev.D60:094016,1999 hep-ph/9905407 PROPOSING 'B PARITY': A NEW APPROXIMATE QUANTUM NUMBER IN INCLUSIVE B JET PRODUCTION, AS AN EFFICIENT PROBE OF NEW FLAVOR PHYSICS. S. Bar-Shalom, J. Wudka hep-ph/9904365
Notes:This talk is probably relevant to various parallel sessions PA-5, PA-7, PA-10 and PA-11
A smoking gun signature is provided for AMSB models with the LSP being nearly mass-degenerate with the chargino, both being Winos. The signal is a fast charged electron (muon) trigger, a resolved soft pion impact parameter and overall misssing transverse energy from selectron (smuon) pair production in a next-generation Linear Collider.
Authors:Dilip Kumar Ghosh, Probir Roy and Sourov Roy
Proposed speaker: Probir Roy
Contact person:Probir Roy
(Tata Institute of Fundamental Reasearch),
probir@tifr.res.in
Sessions: PA-11 Search for New Particles and New Phenomena / PL-07a Search for New Particles and New Phenomena (Results from e+e- Colliders)
Supporting papers:
Notes:
Phenomenology of a radion ($\phi$) that stabilizes the modulus in the Randall-Sundrum scenario is considered. The radion couples to the trace of energy momentum tensor of the standard model (SM) with a strength suppressed only by a new scale ($\Lambda_{\phi}$) of an order of the electroweak scale. In particular, the effective coupling of a radion to two gluons are enhanced due to the trace anomaly of QCD. Therefore, its production cross section at hadron colliders could be enhanced, and the dominant decay mode of a relatively light radion is $\phi$ -> g g, unlike the SM Higgs boson case. We also present constraints on the mass $m_{\phi}$ and the new scale $\Lambda_{\phi}$ from the Higgs search limit at LEP and perturbative unitarity bound.
Authors:Saebyok Bae, P. Ko, Hong Seok Lee, Jungil Lee
Proposed speaker: Pyungwon Ko
Contact person:Pyungwon Ko
(KAIST),
pko@muon.kaist.ac.kr
Sessions: PA-11 Search for New Particles and New Phenomena / PL-07b Search for New Particles and New Phenomena (Results from Hadron Colliders)
Supporting papers: (1) Saebyok Bae, P. Ko, Hong Seok Lee, Jungil Lee, KAIST-TH 00/1, DESY 00-030, hep-ph/0002224
Notes:
We analyze the potentiality of the CERN Large Hadron Collider to probe the Higgs boson couplings to the electroweak gauge bosons. We parametrize the possible deviations of these couplings due to new physics in a model independent way, using the most general dimension--six effective lagrangian where the SU(2)_L x U(1)_Y is realized linearly. For intermediate Higgs masses, the decay channel into two photons is the most important one for Higgs searches at the LHC. We study the effects of these new interactions on the Higgs production mechanism and its subsequent decay into two photons. We show that the LHC will be sensitive to new physics scales beyond the present limits extracted from the LEP and Tevatron physics.
Authors:O.J.P. Eboli, M.C. Gonzalez-Garcia , S.M . Lietti , S.F. Novaes
Proposed speaker: concha gonzalez-garcia
Contact person:concha gonzalez-garcia
(Universidad de Valencia-CSIC),
concha@flamenco.ific.uv.es
Sessions: PA-11 Search for New Particles and New Phenomena /
Supporting papers: hep-ph/0001030
Notes:
The data collected by DELPHI in 1999 at the centre-of-mass energies of 192, 196, 200 and 202 GeV were used to update the search for charginos nearly mass-degenerate with the lightest neutralino, supposed to be the LSP. Depending on the chargino lifetime, three different experimental techniques were used: search for heavy stable charged particles; search for decays inside the fiducial volume of the tracking detectors of DELPHI; search for soft particles accompanied by intial state photon radiation. No excess of events above the Standard Model expectations was observed, and exclusions in the plane mass difference versus chargino mass are given.
Authors:DELPHI Collaboration
Proposed speaker:
Contact person:Clara Matteuzzi
(),
Clara.Matteuzzi@cern.ch
Sessions: PA-11 Search for New Particles and New Phenomena / PL-07a Search for New Particles and New Phenomena (Results from e+e- Colliders)
Supporting papers:
Notes:Paper will be sent later 5/23/00 TY-Removed doubled abstract, #293, based on request by Clara.
Final states with isolated photons were explored in order to search for Higgs bosons with non fermionic couplings. The data collected by the DELPHI detector at centre-of-mass energies ranging from 192 GeV to 202 GeV corresponding to a total integrated luminosity of 230 pb$^{-1}$ were analysed. No evidence for a signal was found and confidence limits were derived in the framework of possible extensions of the SM Higgs sector.
Authors:DELPHI Collaboration
Proposed speaker:
Contact person:Clara Matteuzzi
(),
Clara.Matteuzzi@cern.ch
Sessions: PA-11 Search for New Particles and New Phenomena / PL-07a Search for New Particles and New Phenomena (Results from e+e- Colliders)
Supporting papers:
Notes:Paper will be sent later
Searches for single production of scalar and vector leptoquarks have been performed using the data collected by the DELPHI detector at LEP up to sqrt(s)=202 GeV. Limits, at 95 % confidence level, were derived on the masses and couplings of the leptoquark states within two different frameworks based on the direct (pertubative) and on the resolved photon contribution approaches.
Authors:DELPHI Collaboration
Proposed speaker:
Contact person:Clara Matteuzzi
(),
Clara.Matteuzzi@cern.ch
Sessions: PA-11 Search for New Particles and New Phenomena / PL-07a Search for New Particles and New Phenomena (Results from e+e- Colliders)
Supporting papers:
Notes:Paper will be sent later
Searches for production of supersymmetric particles under the assumption of non-conservation of R-parity have been performed using the data collected by the DELPHI experiment at LEP in e+e- collisions at centre-of-mass energies of 192, 196, 200 and 202 GeV. No excess of data above Standard Model expectations was observed. The results were used to constrain the MSSM parameter space.
Authors:DELPHI Collaboration
Proposed speaker:
Contact person:Clara Matteuzzi
(),
Clara.Matteuzzi@cern.ch
Sessions: PA-11 Search for New Particles and New Phenomena / PL-07a Search for New Particles and New Phenomena (Results from e+e- Colliders)
Supporting papers:
Notes:Paper will be sent later
Using the data taken by the DELPHI detector between energies of 192 and of 202 GeV a search is made for heavy stable or long-lived charged particles. The Cherenkov light detected in the RICH and the ionisation loss measured in the TPC are used to distinguish possible signal events from background. As no indication for a signal production is observed, the results are used to derive limits on the cross sections and masses of stable or long-lived smuons and staus.
Authors:DELPHI Collaboration
Proposed speaker:
Contact person:Clara Matteuzzi
(),
Clara.Matteuzzi@cern.ch
Sessions: PA-11 Search for New Particles and New Phenomena / PL-07a Search for New Particles and New Phenomena (Results from e+e- Colliders)
Supporting papers:
Notes:Paper will be sent later
In supersymmetric models, the gluino could be light and stable, and because of its colour charge, it hadronizes to form R-hadrons. Data collected by the DELPHI detector at centre-of-mass energy of 192 to 202 GeV corresponding to an integrated luminosity of 226 pb-1 have been used to search for R-hadrons in stop decay. The observed number of events is in agreement with the Standard Model predictions. Results are presented in terms of excluded regions in the plane {mass(stop),mass(gluino)}.
Authors:DELPHI Collaboration
Proposed speaker:
Contact person:Clara Matteuzzi
(),
Clara.Matteuzzi@cern.ch
Sessions: PA-11 Search for New Particles and New Phenomena / PL-07a Search for New Particles and New Phenomena (Results from e+e- Colliders)
Supporting papers:
Notes:Paper will be sent later
An update of limits on the masses of supersymmetric particles: the lightest neutralino, the lightest chargino, the next-to-lightest neutralino, the sneutrino, and the right-handed selectron, is presented, based on 227 pb-1 of data collected by DELPHI in 1999, at centre-of-mass energies from 192 to 202 GeV. The limits are set within the MSSM framework with R-parity conservation.
Authors:DELPHI Collaboration
Proposed speaker:
Contact person:Clara Matteuzzi
(),
Clara.Matteuzzi@cern.ch
Sessions: PA-11 Search for New Particles and New Phenomena / PL-07a Search for New Particles and New Phenomena (Results from e+e- Colliders)
Supporting papers:
Notes:Paper will be sent later
This note updates previous results on exotic and supesymmetric particles searches from the DELPHI experiment at LEP 2 with preliminary results from the recent data taken in 2000.
Authors:DELPHI Collaboration
Proposed speaker:
Contact person:Clara Matteuzzi
(),
Clara.Matteuzzi@cern.ch
Sessions: PA-11 Search for New Particles and New Phenomena / PL-07a Search for New Particles and New Phenomena (Results from e+e- Colliders)
Supporting papers:
Notes:Paper will be sent later
Searches for productions of the scalar supersymmetric partner of the goldstino, the sgoldstino, are performed using the data collected by the ALEPH detector at LEP2. The results are interpreted in the framework of effective theories of a supersymmetric extension of the Standard Model with a very light gravitino.
Authors:ALEPH collaboration
Proposed speaker:
Contact person:Fabrizio Palla
(CERN),
Fabrizio.Palla@cern.ch
Sessions: PA-11 Search for New Particles and New Phenomena / PL-07a Search for New Particles and New Phenomena (Results from e+e- Colliders)
Supporting papers:
Notes:
Searches for the production of supersymmetric particles under the assumption that R-parity is violated via a single dominant LLE, LQD or UDD coupling are performed using the data collected by the ALEPH collaboration at a centre-of-mass energy between 189 and 202 GeV. The number of candidate events observed in the data are in agreement with Standard Model expectations. Upper limits on the production cross-sections and lower limits on the masses of charginos, sleptons, squarks and sneutrinos are derived.
Authors:ALEPH collaboration
Proposed speaker:
Contact person:Fabrizio Palla
(CERN),
Fabrizio.Palla@cern.ch
Sessions: PA-11 Search for New Particles and New Phenomena / PL-07a Search for New Particles and New Phenomena (Results from e+e- Colliders)
Supporting papers:
Notes:
Data collected at centre-of-mass energies from 189 GeV to 202 GeV by ALEPH at LEP, corresponding to an integrated luminosity of 411 pb-1, are analysed in a search for the scalar top in the decay channels "stop-->c/u+neutralino" for small mass differences between the stop and the lightest neutralino. No evidence for deviations from the Standard Model expectation is found and a lower limit of 59 GeV/c^2 is set for the stop mass, independent of the stop to neutralino mass difference and of the stop decay width.
Authors:ALEPH collaboration
Proposed speaker:
Contact person:Fabrizio Palla
(CERN),
Fabrizio.Palla@cern.ch
Sessions: PA-11 Search for New Particles and New Phenomena / PL-07a Search for New Particles and New Phenomena (Results from e+e- Colliders)
Supporting papers:
Notes:
Results are presented from a search for topologies characteristic of slepton pair production in Gauge Mediated SUSY breaking scenarios. Data collected with the ALEPH detector at centre-of-mass energies between 192 and 202 GeV. A 95% confidence level lower limit on the stau-right mass is obtained independent of its lifetime.
Authors:ALEPH collaboration
Proposed speaker:
Contact person:Fabrizio Palla
(CERN),
Fabrizio.Palla@cern.ch
Sessions: PA-11 Search for New Particles and New Phenomena / PL-07a Search for New Particles and New Phenomena (Results from e+e- Colliders)
Supporting papers:
Notes:
The production of final states involving only one or more energetic photons from e+e- collisions is studied in a sample of 410 pb^-1 of data recorded at centre-of-mass energies between 189 and 202 GeV. The e+e- -> nunu gamma and e+e- -> gammagamma(gamma) cross sections are measured. The data are in good agreement with predictions based on the Standard Model and are used to set upper limits on the cross sections for additional photon production in the context of supersymmetric models and theories with quantum gravity propagating in extra spatial dimensions, and limits on parameters characterising various modifications to QED.
Authors:ALEPH collaboration
Proposed speaker:
Contact person:Fabrizio Palla
(CERN),
Fabrizio.Palla@cern.ch
Sessions: PA-11 Search for New Particles and New Phenomena / PL-07a Search for New Particles and New Phenomena (Results from e+e- Colliders)
Supporting papers:
Notes:
Searches for topologies characteristic of Gauge Mediated SUSY Breaking (GMSB) models are performed by analysing 173.6~pb^-1 of data collected at a centre-of-mass energy of 189 GeV. These topologies include acoplanar photons, non-pointing single photon, acoplanar leptons, large impact parameter leptons, detached slepton decay vertices, heavy stable charged sleptons and four leptons plus missing energy final states. A scan of a minimal GMSB parameter space is performed and model dependent lower limits of about 45 GeV/c^2 on the next-to-lightest supersymmetric particle (NLSP) mass and of about 9 TeV on the mass scale parameter Lambda are derived, independently of the NLSP lifetime.
Authors:ALEPH collaboration
Proposed speaker:
Contact person:Fabrizio Palla
(CERN),
Fabrizio.Palla@cern.ch
Sessions: PA-11 Search for New Particles and New Phenomena / PL-07a Search for New Particles and New Phenomena (Results from e+e- Colliders)
Supporting papers: CERN-EP 99-171
Notes:
In the framework of the constrained MSSM, a scan on the four fundamental SUSY parameters, tan(beta), mu, M2 and m0 has been made to set an absolute limit on the mass of the selectron, the partner of the electron in SUSY theories. Results from direct searches, obtained from data collected by the ALEPH experiment at LEP at center of mass energies up to 202 GeV, are combined with those from chargino and neutralino searches to exclude also regions of parameter space which, due to cascade decays, cannot be covered by direct searches alone.
Authors:ALEPH collaboration
Proposed speaker:
Contact person:Fabrizio Palla
(CERN),
Fabrizio.Palla@cern.ch
Sessions: PA-11 Search for New Particles and New Phenomena / PL-07a Search for New Particles and New Phenomena (Results from e+e- Colliders)
Supporting papers:
Notes:
Evidence for the cascade decays neutralino -> slepton lepton -> lepton gravitino lepton in GMSB models has been sought in data taken with ALEPH at LEP. Results up to a centre of mass energy of 202 GeV are presented, considering various possible mass differences and the following topologies smuon smuon, selectron selectron, stau stau, smuon selectron, smuon stau, selectron stau. The slepton lifetime is assumed to be negligible.
Authors:ALEPH collaboration
Proposed speaker:
Contact person:Fabrizio Palla
(CERN),
Fabrizio.Palla@cern.ch
Sessions: PA-11 Search for New Particles and New Phenomena / PL-07a Search for New Particles and New Phenomena (Results from e+e- Colliders)
Supporting papers:
Notes:
Data collected by the ALEPH experiment at LEP at various center-of-mass energies in the range between 189 and 202 GeV have been used to analyse the impact of stau mixing in the MSSM on the chargino and neutralino limits. The standard chargino analyses have been performed together with a search for chargino decays via sleptons, including tau-tau final states. The effects of stau mixing are studied in detail in the deep gaugion region (mu = -500 GeV), for which exclusion limits as a function of the mixing angle phi-tau, tan-beta and m-zero are given in the sneutrino-chargino mass plane.
Authors:ALEPH collaboration
Proposed speaker:
Contact person:Fabrizio Palla
(CERN),
Fabrizio.Palla@cern.ch
Sessions: PA-11 Search for New Particles and New Phenomena / PL-07a Search for New Particles and New Phenomena (Results from e+e- Colliders)
Supporting papers:
Notes:
A search for chargino decays to the lightest neutralino, characterized by a very small mass difference between the two particles, is performed using data collected at centre-of-mass energies up to 202 GeV.
Authors:ALEPH collaboration
Proposed speaker:
Contact person:Fabrizio Palla
(CERN),
Fabrizio.Palla@cern.ch
Sessions: PA-11 Search for New Particles and New Phenomena / PL-07a Search for New Particles and New Phenomena (Results from e+e- Colliders)
Supporting papers:
Notes:
Searches for supersymmetric particles have been performed in the data collected with the ALEPH detector at the highest centre-of-mass energy achieved by LEP during the year 2000 data taking period. Preliminary results are presented.
Authors:ALEPH collaboration
Proposed speaker:
Contact person:Fabrizio Palla
(CERN),
Fabrizio.Palla@cern.ch
Sessions: PA-11 Search for New Particles and New Phenomena / PL-07a Search for New Particles and New Phenomena (Results from e+e- Colliders)
Supporting papers:
Notes:
Results are presented from a search for topologies characteristic of slepton pair production in Gauge Mediated SUSY breaking scenarios. Data collected with the ALEPH detector at centre-of-mass energies between 192 and 202 GeV. A 95% confidence level lower limit on the stau-right mass is obtained independent of its lifetime.
Authors:ALEPH collaboration
Proposed speaker:
Contact person:Fabrizio Palla
(CERN),
Fabrizio.Palla@cern.ch
Sessions: PA-11 Search for New Particles and New Phenomena / PL-07a Search for New Particles and New Phenomena (Results from e+e- Colliders)
Supporting papers:
Notes:
We report on the preliminary status of searches for new particles with the L3 detector at LEP from data collected during the year 2000 at increased center-of-mass energies. Searches for Higgs bosons, Supersymmetric particles and new heavy leptons are summarised.
Authors:L3 Collaboration
Proposed speaker: L3 speaker
Contact person:Simonetta Gentile
(CERN),
Simonetta.Gentile@cern.ch
Sessions: PA-11 Search for New Particles and New Phenomena / PL-07a Search for New Particles and New Phenomena (Results from e+e- Colliders)
Supporting papers:
Notes:in preparation
We have searched the muon momentum spectrum from pion decay-in-flight for evidence of a hitherto unknown neutral particle X, with a mass of 33.9 MeV. This process was suggested by the KARMEN collaboration as an explanation for a ‘long-standing’ anomaly in their data of neutrino induced reactions originating from stopped pion and muon decays [1]. Using the advantages of a decay-in-flight experiment to kinematically separate muons associated with an X-particle from those originating from normal pion decay, we find no evidence for such a process at a sensitivity of a few parts in 10**10. Our final results will be reported.
Authors:P.-R. Kettle, M. Daum, M. Janousch, J. Koglin, D. Pocanic, J. Schottmueller, C. Wigger, Z.G. Zhao
Proposed speaker: P.-R. Kettle
Contact person:Peter-Raymond Kettle
(Paul Scherrer Institute),
peter-raymond.kettle@psi.ch
Sessions: PA-11 Search for New Particles and New Phenomena / PL-08a Neutrino Physics (Accelerator and Reactor Neutrino Experiments)
Supporting papers: Reference [1] B. Armbruster at al., Phys. Lett. B 348 (1995) 19.
Notes:
A search for the lightest neutral scalar and neutral pseudoscalar Higgs bosons in the Minimal Supersymmetric Standard Model is performed using all of the data collected by L3 at center-of-mass energies up to 202 GeV at LEP. The data are evaluated for representative scans of the SUSY parameters. Limits on the masses of the lightest neutral scalar and pseudoscalar are given as a function of tan(beta). Lower mass limits independent of tan(beta) are also set.
Authors:L3 Collaboration
Proposed speaker: L3 speaker
Contact person:Simonetta Gentile
(CERN),
Simonetta.Gentile@cern.ch
Sessions: PA-11 Search for New Particles and New Phenomena / PL-07a Search for New Particles and New Phenomena (Results from e+e- Colliders)
Supporting papers:
Notes:in preparation
A search for the Standard Model Higgs boson is carried out on all of the data collected by the L3 detector at center-of-mass energies up to 202 GeV at LEP. A lower limit on the mass of the Standard Model Higgs boson is set.
Authors:L3 Collaboration
Proposed speaker: L3 speaker
Contact person:Simonetta Gentile
(CERN),
Simonetta.Gentile@cern.ch
Sessions: PA-11 Search for New Particles and New Phenomena / PL-07a Search for New Particles and New Phenomena (Results from e+e- Colliders)
Supporting papers:
Notes:in preparation
A search is performed for a non-standard Higgs particle through the processes e+e- -> H gamma, e+e- -> HZ and e+e- -> H e+e- with the L3 detector at LEP. The Higgs decays H -> bb, H -> Z gamma and H -> gamma gamma are considered. These results are interpreted in terms of anomalous WWV couplings and other anomalous couplings in the Higgs sector.
Authors:L3 Collaboration
Proposed speaker: L3 speaker
Contact person:Simonetta Gentile
(CERN),
Simonetta.Gentile@cern.ch
Sessions: PA-11 Search for New Particles and New Phenomena / PL-07a Search for New Particles and New Phenomena (Results from e+e- Colliders)
Supporting papers:
Notes:in preparation
A search for pair-produced charged Higgs bosons is performed with the L3 detector at center-of-mass energies up to 202 GeV at LEP. Higgs decays into a charm and a strange quark or into a tau lepton and its associated neutrino are considered. Lower limits on the mass of the charged Higgs boson are set as a function of the decay branching ratio. A mass limit independent of the branching ratio is also established.
Authors:L3 Collaboration
Proposed speaker: L3 speaker
Contact person:Simonetta Gentile
(CERN),
Simonetta.Gentile@cern.ch
Sessions: PA-11 Search for New Particles and New Phenomena / PL-07a Search for New Particles and New Phenomena (Results from e+e- Colliders)
Supporting papers:
Notes:in preparation
A search is performed for a Higgs boson, decaying into two photons, using the data collected by the L3 detector at center-of-mass energies up to 202 GeV at LEP. The process e+e- -> HZ -> qq gamma gamma is considered. Limits on the rate of the Higgs boson decay into two photons as a function of the Higgs mass are presented.
Authors:L3 Collaboration
Proposed speaker: L3 speaker
Contact person:Simonetta Gentile
(CERN),
Simonetta.Gentile@cern.ch
Sessions: PA-11 Search for New Particles and New Phenomena / PL-07a Search for New Particles and New Phenomena (Results from e+e- Colliders)
Supporting papers:
Notes:in preparation
A search for a non-standard Higgs boson produced in the Higgsstrahlung process and decaying hadronically is carried out on all of the data collected by the L3 detector at center-of-mass energies up to 202 GeV at LEP. The search is performed independently of the flavor of the Higgs hadronic decay products. Lower limits on the Higgs mass are set as a function of the branching ratio. A lower limit on the mass is also derived in the case of a two-doublet Higgs model of Type II.
Authors:L3 Collaboration
Proposed speaker: L3 speaker
Contact person:Simonetta Gentile
(CERN),
Simonetta.Gentile@cern.ch
Sessions: PA-11 Search for New Particles and New Phenomena / PL-07a Search for New Particles and New Phenomena (Results from e+e- Colliders)
Supporting papers:
Notes:in preparation
A search for a non-minimal Higgs boson produced in the Higgsstrahlung process and decaying into undetectable particles is performed using the data collected by the L3 experiment at center-of-mass energies up to 202 GeV at LEP. The decays of the Z bosons into qq, ee and mumu are considered. Lower limits on the Higgs mass are set as a function of the Higgs branching ratio into invisible particles assuming the cross-section for the Higgsstrahlung process.
Authors:L3 Collaboration
Proposed speaker: L3 speaker
Contact person:Simonetta Gentile
(CERN),
Simonetta.Gentile@cern.ch
Sessions: PA-11 Search for New Particles and New Phenomena / PL-07a Search for New Particles and New Phenomena (Results from e+e- Colliders)
Supporting papers:
Notes:in preparation
Searches for the production of sfermions, charginos and neutralinos have been performed using data collected by the ALEPH detector at centre-of-mass energies up to 201.6 GeV. Improved constraints in the space of the relevant parameters are derived from the non-observation of any such a signal. A lower limit on the LSP mass, valid for any Tan(Beta) and sfermion mass, is set using the GUT relations in the gaugino and sfermion sectors. Tighter constraints on the model parameters are obtained including the negative results of Higgs searches. The results are finally interpreted within the framework of Minimal Supergravity.
Authors:ALEPH collaboration
Proposed speaker:
Contact person:Fabrizio Palla
(CERN),
Fabrizio.Palla@cern.ch
Sessions: PA-11 Search for New Particles and New Phenomena / PL-07a Search for New Particles and New Phenomena (Results from e+e- Colliders)
Supporting papers:
Notes:
We report the results of the searches for charginos and neutralinos, assuming R-parity conservation, in e+e- collisions at centre-of-mass energies between 192 GeV and 202 GeV at LEP. No evidence for these supersymmetric particles is found in a data sample corresponding to an integrated luminosity of 233 pb-1. Improved upper limits on the production cross sections of these particles and new lower limits on their masses are set. New exclusion contours in the parameter space of the Minimal Supersymmetric Standard Model are derived. Under the assumptions of common gaugino and scalar masses at the GUT scale, we set absolute lower limits on the masses of the lightest neutralino and of the lightest chargino. New investigations on the effect of large mixings in the stau sector are also performed.
Authors:L3 Collaboration
Proposed speaker: L3 speaker
Contact person:Simonetta Gentile
(CERN),
Simonetta.Gentile@cern.ch
Sessions: PA-11 Search for New Particles and New Phenomena / PL-07a Search for New Particles and New Phenomena (Results from e+e- Colliders)
Supporting papers:
Notes:in preparation
A search for charginos nearly mass-degenerate with the lightest supersymmetric particle is performed using a data sample collected at 192--202 GeV, corresponding to an integrated luminosity of 233 pb-1, with the L3 detector. Mass differences between the chargino and the lightest supersymmetric particle below 4 GeV are considered. The presence of a high transverse momentum photon is required to single out the signal from the two-photon interaction background. No evidence for charginos is found and upper limits on the cross section for chargino pair production are set. In the case of heavy scalar leptons, chargino mass limits are obtained for any chargino-neutralino mass difference.
Authors:L3 Collaboration
Proposed speaker: L3 speaker
Contact person:Simonetta Gentile
(CERN),
Simonetta.Gentile@cern.ch
Sessions: PA-11 Search for New Particles and New Phenomena / PL-07a Search for New Particles and New Phenomena (Results from e+e- Colliders)
Supporting papers:
Notes:in preparation
Single and multi-photon events with missing energy are analysed using data collected with the L3 detector at LEP at centre-of-mass energies of 192--202 GeV, for a total of 233 pb-1 of integrated luminosity. The total cross section of the process e+e- --> nu bar(nu)gamma(gamma) is found in agreement with the Standard Model. Deviations are observed as far as the differential cross section is concerned. The multi-photon channel is in agreement with the Standard Model expectation both in the rate and in the two-photon recoil mass distribution. In the latter channel, upper limits on cross sections of supersymmetric processes are set and interpretations in supersymmetric models provide improved limits on the masses of the lightest neutralino.
Authors:L3 Collaboration
Proposed speaker: L3 speaker
Contact person:Simonetta Gentile
(CERN),
Simonetta.Gentile@cern.ch
Sessions: PA-11 Search for New Particles and New Phenomena / PL-07a Search for New Particles and New Phenomena (Results from e+e- Colliders)
Supporting papers:
Notes:in preparation
We present an outlook for possible R-parity violating SUSY search at TeV scale photon-proton colliders. Single production of third generation slepton through the lambda'(ijk) couplings is investigated and compared with the results of resonant sfermion productions at the existing colliders. We show that around hundred stau events per running year can be seen at the proposed collider HERA+LC up to the mass of 200 GeV.
Authors:Z.Z.Aydin, A.Kandemir and A.U.Yilmazer
Proposed speaker: Z.Z.Aydin
Contact person:Zekeriya Z. Aydin
(Ankara Univ.),
zzaydin@science.ankara.edu.tr
Sessions: PA-11 Search for New Particles and New Phenomena /
Supporting papers:
Notes:
The production of supersymmetric particles in TeV scale polarized photon-proton collisions is discussed. Polarizations of both photon and proton beams are considered. Associated productions of squark-chargino and squark-gluino,and production of squark pairs have been examined. Altough the cross sections for different initial beam polarizations do not differ much, the polarization asymmetry is sensitive to the sparticle mass. We conclude that the capacity of future linac-ring type TeV scale photon-proton colliders is quite promising in the search for SUSY particles.
Authors:Z.Z.Aydin, A.Kandemir O.Yilmaz and A.U.Yilmazer
Proposed speaker: Z.Z.Aydin
Contact person:Zekeriya Z. Aydin
(Ankara Univ.),
zzaydin@science.ankara.edu.tr
Sessions: PA-11 Search for New Particles and New Phenomena /
Supporting papers: 1.Squark-chargino production in polarized gamma-proton collisions at TeV energy scale, Z.Z.Aydin and O.Yilmaz, Europhys.Lett.50(2000)22 2.Pair production of squarks in TeV scale polarized gamma-proton collisions A.Kandemir and A.U.Yilmazer, Phys.Lett.B385(1996)143 3.Gluino-squark production in TeV scale polarized gamma-proton collisions A.Kandemir and A.U.Yilmazer, Il Nuovo Cim.112A(1999)597
Notes:
A search for supersymmetric particles production in e+e- collisions at center-of-mass energies between 189 GeV and 202 GeV is performed under the assumptions that R-parity is not conserved. No signal is found. Limits on the production cross sections, on the Minimal Supersymmetric Standard Model parameters and on the masses of the supersymmetric particles are derived.
Authors:L3 Collaboration
Proposed speaker: L3 speaker
Contact person:Simonetta Gentile
(CERN),
Simonetta.Gentile@cern.ch
Sessions: PA-11 Search for New Particles and New Phenomena / PL-07a Search for New Particles and New Phenomena (Results from e+e- Colliders)
Supporting papers:
Notes:in preparation
We report the result of a search, assuming R-parity conservation, for scalar leptons in e+e- collisions at centre-of-mass energies of 192--202 GeV at LEP. No evidence for such particles is found in a data sample corresponding to an integrated luminosity of 233 pb-1. Moreover a study of the single-electron channel, where the scalar partner of the right-handed electron together with the scalar partner of left-handed electron or the scalar partner of the right-handed electron together with one neutralino are produced, is performed. Improved upper limits are set on the production cross sections for most of scalar leptons. New exclusion contours in the parameter space of the Minimal Supersymmetric Standard Model are derived, as well as new lower limits on the masses of scalar leptons.
Authors:L3 Collaboration
Proposed speaker: L3 speaker
Contact person:Simonetta Gentile
(CERN),
Simonetta.Gentile@cern.ch
Sessions: PA-11 Search for New Particles and New Phenomena / PL-07a Search for New Particles and New Phenomena (Results from e+e- Colliders)
Supporting papers:
Notes:in preparation
Searches for scalar top and scalar bottom quarks, as well as for mass-degenerate scalar quarks of the first two families are performed, assuming R-parity conservation, at centre-of-mass energies of 192--202 GeV with the L3 detector at LEP. No signals are observed in a data sample corresponding to an integrated luminosity of 233 pb-1. Model-independent limits on the scalar top production cross sections are determined for the decay modes s-top_1 ---> c neutralino_1 and s-top_1---> b l s-neutrino (l= e,mu,tau). For scalar quarks of the other flavours s-quark ---> quark neutralino_1 decays are considered. Within the framework of the Minimal Supersymmetric Standard Model mass limits are set at 95\% C.L. for these particles. Indirect limits on the gluino mass are also derived.
Authors:L3 Collaboration
Proposed speaker: L3 speaker
Contact person:Simonetta Gentile
(CERN),
Simonetta.Gentile@cern.ch
Sessions: PA-11 Search for New Particles and New Phenomena / PL-07a Search for New Particles and New Phenomena (Results from e+e- Colliders)
Supporting papers:
Notes:in preparation
An update of a study of the production of single and multi-photon events in the reactions e+e- ---> photon+invisible~particles and e+e^- ---> 2 photons+invisible particles at energies=192-202 GeV has been made. The data were collected with the DELPHI detector and correspond to a total integrated luminositiy of about 229 pb-1. The absence of an excess of events beyond that expected from Standard Model processes is used to set limits on new physics. A search for a substructure as described by composite models is carried out and limits are set on the production of gravitons as suggested by high-dimensional models. Limits on cross sections and masses of supersymmetric particles like neutralinos and gravitinos, for specific model parameters, are investigated.
Authors:DELPHI Collaboration
Proposed speaker:
Contact person:Clara Matteuzzi
(),
Clara.Matteuzzi@cern.ch
Sessions: PA-11 Search for New Particles and New Phenomena / PL-07a Search for New Particles and New Phenomena (Results from e+e- Colliders)
Supporting papers:
Notes:Paper will be sent later
A review of the squark searches achieved by DELPHI at LEP2 is presented here. Squarks were investigated in the MSSM framework looking for squark(b) ---> b+neutralino, squark(t)---> c+neutralino, and squark(t)--->b+sneutrino, which are the dominant decay modes at LEP2. Moreover, other cases were explored such as squark(t)---> c+gluino, if the gluino is assumed to be the LSP (as for instance in GMSB framework or in some SUGRA models), and the case of a stop degenerated in mass with the LSP. Looking to such possibilities also demonstrate the specifics of e+e- machines as compared to pp colliders. The squark searches were completed in a large range of the available MSSM parameter space and limits are pushed at almost the kinematical limits of LEP2.
Authors:DELPHI Collaboration
Proposed speaker:
Contact person:Clara Matteuzzi
(),
Clara.Matteuzzi@cern.ch
Sessions: PA-11 Search for New Particles and New Phenomena / PL-07a Search for New Particles and New Phenomena (Results from e+e- Colliders)
Supporting papers:
Notes:Paper will be sent later
The latest experimental results suggest that the neutrinos of the Standard Model are light but massive and hence they may mix each other, giving rise to lepton flavour or even lepton number violating processes, depending on their Dirac or Majorana nature, respectively. Furthermore, the lightness of the observed neutrinos may be explained by the existence of heavy ones, whose effects on lepton flavour violation would be very sizeable. In this work we present a model-independent analysis of the impact of massive neutrinos on flavour changing decays of the Z boson into leptons, at the one-loop level. Likewise, we carry out a complementary analysis of the effects from virtual supersymmetric particles. Both studies are well motivated in the context of the Giga-Z option of the Tesla Linear Collider project. Constraints from present experiments are taken into account.
Authors:J.I. Illana, M. Jack, T. Riemann
Proposed speaker: Jose I. Illana
Contact person:Jose I. Illana
(DESY Zeuthen),
jillana@ifh.de
Sessions: PA-11 Search for New Particles and New Phenomena / PL-07a Search for New Particles and New Phenomena (Results from e+e- Colliders)
Supporting papers: hep-ph/0001273
Notes:
We have searched for the effects of virtual Kaluza-Klein gravitons predicted in the Arkani-Hamed, Dimopulous, Dvali theory of large spatial extra dimensions. Analyzing angular and invariant mass distributions of photon and electron pairs in 127 pb**-1 of data, we found complete agreement with expectations from the Standard Model. There were no anomalous events with high mass and low scattering angle, characteristic of the virtual graviton exchange. We set lower limits on the compactification scale of large extra dimensions between 1.0 and 1.4 TeV for the number of extra dimensions between 2 and 7. These are the most restrictive limits to date on large extra dimensions.
Authors:The DZero Collaboration
Proposed speaker: To be decided by the DZero Collaboration
Contact person:Bernard G. Pope
(Michigan State University),
pope@pa.msu.edu
Sessions: PA-11 Search for New Particles and New Phenomena /
Supporting papers:
Notes:
The negative result of a search for associated gaugino pair production with a trilepton signature at DZero, is reinterpreted in the framework of minimal supergravity models with R-parity violation via leptonic Yukawa couplings. The search used 95 pb**-1 of integrated luminosity of pbar p collisions at sqrt(s)=1.8 TeV.
Authors:The DZero Collaboration
Proposed speaker: To be decided by the DZero Collaboration
Contact person:Bernard G. Pope
(Michigan State University),
pope@pa.msu.edu
Sessions: PA-11 Search for New Particles and New Phenomena /
Supporting papers:
Notes:
We present a search for t->bH+ in ttbar candidate events at DZero based on two methods. The first seeks a decrease in expected signal, which would imply the presence of a non-SM decay of the top quark. This search involves the full data sample of ~110 pb**-1 of ppbar collisions at sqrt(s)=1.8 TeV, collected with the DZero detector between 1992 and 1995. The second method looks for charged Higgs decays to taus (and associated neutrinos), and is based on a 62 pb**-1 subset of the aformentioned data sample.
Authors:The DZero Collaboration
Proposed speaker: Dhiman Chakraborty (DZero and Stony Brook)
Contact person:Bernard G. Pope
(Michigan State University),
pope@pa.msu.edu
Sessions: PA-11 Search for New Particles and New Phenomena /
Supporting papers:
Notes:
We present a quasi-model-independent search for the physics responsible for electroweak symmetry breaking. We define final states to be searched, and construct a rule that identifies a set of relevant variables for any particular final state. A new algorithm (`Sherlock') searches for regions of excess in those variables, and quantifies the significance of any excess found. After demonstrating the sensitivity of the method, we apply it to the semi-inclusive channel emuX collected in 108 pb**-1 of pbar p collisions at sqrt(s)=1.8 TeV at the DZero experiment during 1992-96 at the Fermilab Tevatron. Beyond ttbar and WW production, we find no evidence of new high p_T physics in this sample.
Authors:The DZero Collaboration
Proposed speaker: To be decided by the DZero Collaboration
Contact person:Bernard G. Pope
(Michigan State University),
pope@pa.msu.edu
Sessions: PA-11 Search for New Particles and New Phenomena /
Supporting papers:
Notes:
We report on a search for supersymmetry using the DZero detector. The 1994-1996 data sample of sqrt(s)=1.8 TeV ppbar collisions was analyzed for events containing two leptons (e or mu), two or more jets, and missing transverse energy. Assuming the minimal supergravity model, with A0=0 and mu<0, various thresholds were employed to optimize the search. No events were found beyond expectation from background. We set a lower limit at the 95% CL of 255 GeV for equal mass squarks and gluinos for tanbeta=2, and present exclusion contours in the (m0, m1/2) plane for tanbeta=2 and 6.
Authors:The DZero Collaboration
Proposed speaker: To be decided by the DZero Collaboration
Contact person:Bernard G. Pope
(Michigan State University),
pope@pa.msu.edu
Sessions: PA-11 Search for New Particles and New Phenomena /
Supporting papers:
Notes:
Events in ppbar collisions at sqrt(s)=1.8 TeV with total transverse energy exceeding 500 GeV are used to set limits on quark substructure. The data are consistent with next-to-leading order QCD calculations. We set a lower limit of 2.0 TeV at 95% confidence on the energy scale Lambda_LL for compositeness in quarks, assuming a model with a left-left isoscalar contact interaction term. The limits on Lambda_LL are found to be insensitive to the sign of the interferencce term in the Lagrangian.
Authors:The DZero Collaboration
Proposed speaker: To be decided by the DZero Collaboration
Contact person:Bernard G. Pope
(Michigan State University),
pope@pa.msu.edu
Sessions: PA-11 Search for New Particles and New Phenomena /
Supporting papers:
Notes:
We use effective lagrangians to systematize the interpretation of the signal, should a new scalar particle be discovered. Our method complements the model-by-model approach used widely in the literature, trading the detailed predictive power of individual models for the robustness and breadth of comparison which is permitted by the effective lagrangian approach. We identify the broad categories of models which experiments can most easily distinguish, and identify how popular models appear within these categories.
Authors:C.P. Burgess, J. Matias and M.Pospelov
Proposed speaker: C. Burgess
Contact person:Cliff P Burgess
(McGill University),
cliff@physics.mcgill.ca
Sessions: PA-11 Search for New Particles and New Phenomena / PL-09 Beyond the Standard Model
Supporting papers: A Higgs or Not a Higgs? hep-ph/9912459
Notes:
Extra spatial dimensions are proposed by recent theories that postulate the scale of gravity to be of the same order of the electroweak scale. These theories predict a sizable interaction between gravitons and Standard Model particles. Effects of the interference of this new interactions with the Standard Model amplitudes of boson and fermion pair production are searched for in the data sample collected in e+e- collisions at centre-of-mass energies between 192 GeV and 202 GeV corresponding to an integrated luminosity of 233 pb-1 by the L3 detector. No statistically significant hints for the existence of these effects are found, disfavouring the hypothesis that the scale of this new theory of gravity is of the order of the TeV.
Authors:L3 Collaboration
Proposed speaker: L3 speaker
Contact person:Simonetta Gentile
(CERN),
Simonetta.Gentile@cern.ch
Sessions: PA-11 Search for New Particles and New Phenomena / PL-07a Search for New Particles and New Phenomena (Results from e+e- Colliders)
Supporting papers:
Notes:in preparation
We report on a search for excited electrons, muons, taus and neutrinos in e+ e- collisions at centre-of-mass energies from 192 GeV up to 202 GeV,corresponding to an integrated luminosity of 233 pb-1, using the L3 detector at LEP. No evidence has been found for their existence. From a search for pair production of excited leptons, we determine lower mass limits for excited electrons, muons, taus, and neutrinos. From a search for singly produced excited leptons we derive upper limits on their coupling constants. All results are preliminary.
Authors:L3 Collaboration
Proposed speaker: L3 speaker
Contact person:Simonetta Gentile
(CERN),
Simonetta.Gentile@cern.ch
Sessions: PA-11 Search for New Particles and New Phenomena / PL-07a Search for New Particles and New Phenomena (Results from e+e- Colliders)
Supporting papers:
Notes:in preparation
A search for exotic heavy leptons (sequential, vector, mirror and singlet leptons) is made at center-of-mass energies sqrt(s)= 192 -- 202 GeV with the L3 detector at LEP. No evidence for their existence is found. For pair-produced heavy leptons lower limits on their masses are set. For singly-produced heavy neutrino we set upper limits on the mixing parameter between the heavy and light neutrino
Authors:L3 Collaboration
Proposed speaker: L3 speaker
Contact person:Simonetta Gentile
(CERN),
Simonetta.Gentile@cern.ch
Sessions: PA-11 Search for New Particles and New Phenomena / PL-07a Search for New Particles and New Phenomena (Results from e+e- Colliders)
Supporting papers:
Notes:in preparation
The measurements of hadron and lepton-pair production cross sections and leptonic forward-backward asymmetries performed with the L3 detector at centre-of-mass energies between 130 GeV and 202 GeV, corresponding to an integrated luminosity of approximatly 490 pb-1, are used to search for new physics phenomena such as: contact interactions, exchange of virtual leptoquarks, scalar quarks and scalar neutrinos, effects of TeV strings in models of quantum gravity with large extra dimensions, non-zero sizes of the fermions and additional heavy gauge bosons Z'. No evidence for these phenomena is found and new limits on the parameters of these extensions of the Standard Model are set.
Authors:L3 Collaboration
Proposed speaker: L3 speaker
Contact person:Simonetta Gentile
(CERN),
Simonetta.Gentile@cern.ch
Sessions: PA-11 Search for New Particles and New Phenomena / PL-07a Search for New Particles and New Phenomena (Results from e+e- Colliders)
Supporting papers:
Notes:in preparation
It has been proposed that gravity may become strong at the TeV scale in theories with extra space dimensions. In such models quantum gravity effects may be observable at LEP energies. The effects of virtual graviton exchange is searched for in ZZ and WW production data. No evidence of this new interaction is found and therefore limits on the scale of quantum gravity are set.
Authors:The OPAL collaboration
Proposed speaker:
Contact person:David J Miller
(CERN),
dave.miller@cern.ch
Sessions: PA-11 Search for New Particles and New Phenomena / PL-07a Search for New Particles and New Phenomena (Results from e+e- Colliders)
Supporting papers: To be submitted to the conference and listed on http://opal.web.cern.ch/Opal/pubs/publications.html
Notes:Also accepted as abstract 577 for sessions PA-05 and PL-06a, Standard model . 5/15/00 TY-This has higher priority than 577, according to E-mail from Miller dated 5/15.
A search for pair produced charged Higgs bosons was performed in the high energy data collected by the DELPHI detector at LEP II at centre-of-mass energies from 189~GeV to 202~GeV. The three different final states, (tau-nu,tau-nu), (csbar,tau-nu) and (csbar,cbars) were considered. New methods were applied in the rejection of wrong hadronic jet pairings and for the tau identification, where a discriminator based on tau polarisation and polar angles was used. No excess of data compared to the expected Standard Model processes was observed and a lower limit for the charged Higgs boson mass was set.
Authors:DELPHI Collaboration
Proposed speaker:
Contact person:Clara Matteuzzi
(),
Clara.Matteuzzi@cern.ch
Sessions: PA-11 Search for New Particles and New Phenomena / PL-07a Search for New Particles and New Phenomena (Results from e+e- Colliders)
Supporting papers:
Notes:Paper will be sent later
Searches for neutral Higgs bosons in the Standard Model and the MSSM have been performed in the data collected by the DELPHI experiment at centre-of-mass energies between 191.6 and 201.7~GeV with a total integrated luminosity of 228 pb-1. These analyses are used, in combination with our results at lower energies, to set 95% confidence level lower mass bounds on the Standard Model Higgs boson and on the lightest neutral scalar and neutral pseudoscalar Higgs bosons in scans of the MSSM parameter space.
Authors:DELPHI Collaboration
Proposed speaker:
Contact person:Clara Matteuzzi
(),
Clara.Matteuzzi@cern.ch
Sessions: PA-11 Search for New Particles and New Phenomena / PL-07a Search for New Particles and New Phenomena (Results from e+e- Colliders)
Supporting papers:
Notes:Paper will be sent
Results from precision measurements of Standard Model processes at LEP2 are used to set limits on new physics as described by four-fermion contact interactions or by the exchange of a new heavy particle such as a sneutrino in supersymmetric theories with R-parity violation. In the context of models with a heavy Z' boson, limits are placed on the mass of the Z' and the mixing angle between the Z' and the Z. A search for the indirect effects of the gravitational interaction in extra dimensions on the lepton pair, Z pair and W pair final states is also presented.
Authors:The OPAL collaboration
Proposed speaker:
Contact person:David J Miller
(CERN),
dave.miller@cern.ch
Sessions: PA-11 Search for New Particles and New Phenomena / PL-07a Search for New Particles and New Phenomena (Results from e+e- Colliders)
Supporting papers: To be submitted to the conference and listed on http://opal.web.cern.ch/Opal/pubs/publications.html Previous results available as CERN-EP/99-097, accepted by Eur. Phys. J. C =http://opal.web.cern.ch/Opal/pubs/paper/html/pr286.html and as OPAL Physics Note 424 =http://opal.web.cern.ch/Opal/pubs/physnote/html/pn424.html
Notes:Related to abstracts 168 and 184 submitted to sessions PA-05 and PL-6a, Electroweak Gauge Theory
Data collected by the DELPHI experiment at centre-of-mass energies from 192 to 202 GeV with an integrated luminosity of 226 pb-1. have been used to search for the supersymmetric partners of electrons, muons, and taus in the context of the Minimal Supersymmetric Standard Model. We present results in terms of exclusion regions in the (M_slept,M_chi0).
Authors:DELPHI Collaboration
Proposed speaker:
Contact person:Clara Matteuzzi
(),
Clara.Matteuzzi@cern.ch
Sessions: PA-11 Search for New Particles and New Phenomena / PL-07a Search for New Particles and New Phenomena (Results from e+e- Colliders)
Supporting papers:
Notes:Paper will be sent
The production of single photons has been studied in the reaction e+e- ---> gamma+invisible~particles at centre-of-mass energies of 183 GeV and 189 GeV. A previously published analysis of events with multi-photon final states accompanied by missing energy has been updated with 189 GeV data. The data were collected with the DELPHI detector and correspond to integrated luminosities of about 51 pb-1 and 158 pb-1 at the two energies. The number of light neutrino families is measured to be 2.84+-0.15(stat)+-0.14(syst). The absence of an excess of events beyond that expected from Standard Model processes is used to set limits on new physics as described by supersymmetric and composite models. A limit on the gravitational scale is also determined.
Authors:DELPHI Collaboration
Proposed speaker:
Contact person:Clara Matteuzzi
(),
Clara.Matteuzzi@cern.ch
Sessions: PA-11 Search for New Particles and New Phenomena / PL-07a Search for New Particles and New Phenomena (Results from e+e- Colliders)
Supporting papers:
Notes:Paper will be sent
A search for pair-production of neutralinos at a LEP centre-of-mass energy of 189 GeV has been performed. No signal was found and limits on the neutralino production cross-section at 95% confidence level were obtained. These limits have been used to exclude regions in the parameter space of the MSSM.
Authors:DELPHI Collaboration
Proposed speaker:
Contact person:Clara Matteuzzi
(),
Clara.Matteuzzi@cern.ch
Sessions: PA-11 Search for New Particles and New Phenomena / PL-07a Search for New Particles and New Phenomena (Results from e+e- Colliders)
Supporting papers:
Notes:Paper will be sent
Searches for supersymmetric partners of top and bottom quarks are presented using data taken by the DELPHI experiment at LEP in 1997 and 1998. No deviations from standard model expectations are observed in these data sets, which are taken at centre-of-mass energies of 183 GeV and 189 GeV and correspond to integrated luminosities of 54 pb-1 and 158 pb-1. These results are used in combination with those obtained by DELPHI at lower centre-of-mass energies to exclude regions in the squark-neutralino mass plane at 95% confidence level.
Authors:DELPHI Collaboration
Proposed speaker:
Contact person:Clara Matteuzzi
(),
Clara.Matteuzzi@cern.ch
Sessions: PA-11 Search for New Particles and New Phenomena / PL-07a Search for New Particles and New Phenomena (Results from e+e- Colliders)
Supporting papers:
Notes:Paper will be sent
Searches for pair production of gauginos and squarks in e+e- collisions at a centre-of-mass energy of 189 GeV have been performed on data corresponding to an integrated luminosity of 158 pb-1 collected by the DELPHI detector at LEP. The data were analyzed under the assumption of non-conservation of R-parity through a single dominant UbarDbarDbar coupling between squarks and quarks. Typical final states contain between 4 and 10 jets with or without additional leptons. No excess of data above Standard Model expectations was observed. The results were used to constrain domains of the MSSM parameter space and derive limits on the masses of supersymmetric particles. The following mass limits at 95% CL were obtained from these searches: neutralino mass > 32 GeV chargino mass > 94 GeV stop and sbottom mass (indirect decay) with DM > 5 GeV: m_stop > 74 GeV, for Phi_mix=0 rad m_stop > 59 GeV, for Phi_mix=0.98 rad m_sbott> 72 GeV, for Phi_mix=0 rad.
Authors:DELPHI Collaboration
Proposed speaker:
Contact person:Clara Matteuzzi
(),
Clara.Matteuzzi@cern.ch
Sessions: PA-11 Search for New Particles and New Phenomena / PL-07a Search for New Particles and New Phenomena (Results from e+e- Colliders)
Supporting papers:
Notes:Paper will be sent
Searches for pair production of supersymmetric particles under the assumption that R-parity is not conserved are presented, based on data recorded by the DELPHI detector in 1998 in e+e- collisions at centre-of-mass energy of 189 GeV. Only one R-parity violating LLEbar term (i.e. one lambda coupling), which couples scalar leptons to leptons, is considered to be dominant at a time. Moreover, it is assumed that the strength of the R-parity violating couplings is such that the lifetimes can be neglected. The search for pair production of neutralinos, charginos and sleptons has been performed for both direct R-parity violating decays and indirect cascade decays. The results are in agreement with Standard Model expectations, and are used to update the constraints on the MSSM parameter values and the mass limits previously derived at 183 GeV.
Authors:DELPHI Collaboration
Proposed speaker:
Contact person:Clara Matteuzzi
(),
Clara.Matteuzzi@cern.ch
Sessions: PA-11 Search for New Particles and New Phenomena / PL-07a Search for New Particles and New Phenomena (Results from e+e- Colliders)
Supporting papers:
Notes:Paper will be sent
Searches for spontaneous R-parity violating signals at energies=183 GeV and 189 GeV have been performed in 1997 and 1998 DELPHI data, under the assumption of R-parity breaking in the third lepton family. The expected topology for the decay of a pair of charginos into two acoplanar taus plus missing energy was investigated and no evidence of signal was found. The results were used to derive a limit on the chargino mass and to constrain domains of the MSSM parameter space.
Authors:DELPHI Collaboration
Proposed speaker:
Contact person:Clara Matteuzzi
(),
Clara.Matteuzzi@cern.ch
Sessions: PA-11 Search for New Particles and New Phenomena / PL-07a Search for New Particles and New Phenomena (Results from e+e- Colliders)
Supporting papers:
Notes:Paper will be sent
Data taken by the DELPHI experiment at centre-of-mass energies of 183 GeV and 189 GeV and an integrated luminosity of 212 pb-1 have been used to search for the supersymmetric partners of the electrons, muons, and taus in the context of the Minimal Supersymmetric Standard Model (MSSM). The decay topologies searched for were the direct decay slept ---> l+chi0 producing acoplanar lepton pairs plus missing energy, and the cascade decay slept ---> l+chi0_2 ---> l+g+chi0_1 producing acoplanar lepton and photon pairs plus missing energy. The observed number of events is in agreement with Standard Model predictions. The 95% CL excluded mass limits on the masses for selectrons, smuons and staus at large values of M_slep-M are M_sel > 87 GeV/c2, M_smu > 80 GeV/c2 and M_stau > 75 GeV/c2 respectively for values of mu=-200 GeV/c2 and tan(beta)=1.5. The lower limit on M_stau for any mixing-angle and for all M_slep-M > m_tau is 12.5 GeV/c2.
Authors:DELPHI Collaboration
Proposed speaker:
Contact person:Clara Matteuzzi
(),
Clara.Matteuzzi@cern.ch
Sessions: PA-11 Search for New Particles and New Phenomena / PL-07a Search for New Particles and New Phenomena (Results from e+e- Colliders)
Supporting papers:
Notes:Paper will be sent later
We report on the search for single top production in e+e- collisions using the data collected by L3 at sqrt{s}>189GeV. We present two independent analysis in the purely hadronic and semileptonic top decay channels.
Authors:L3 Collaboration
Proposed speaker: L3 speaker
Contact person:Simonetta Gentile
(CERN),
Simonetta.Gentile@cern.ch
Sessions: PA-11 Search for New Particles and New Phenomena / PL-07a Search for New Particles and New Phenomena (Results from e+e- Colliders)
Supporting papers:
Notes:in preparation
The exchange of FCNC bosons leads both to rare hadron decays and $\mu-e$ conversions and, at ultra high energies, to new interactions for neutrinos offering a possible explanation for post-GZK air showers in cosmic rays. Here, these effects are jointly anlysed within the Dualized Standard Model framework we advocate. With parameters already used successfully to calculate quark mixing and neutrino oscillations, all FCNC effects now depend on only the exchanged boson mass, which if chosen $\sim$ 400 TeV, fits the bounds in all 3 areas, while giving concrete predictions in experimental regions soon to be explored.
Authors:Jose BORDES, CHAN Hong-Mo, TSOU Sheung Tsun
Proposed speaker: Jose BORDES or CHAN Hong-Mo
Contact person:Hong-Mo Chan
(Rutherford Appleton Laboratory),
chanhm@v2.rl.ac.uk
Sessions: PA-11 Search for New Particles and New Phenomena / PL-02 CP Violation and Rare Decays ( Kaon, Muon )
Supporting papers: Astroparticl Phys 8 (1998) 135 hep-ph/9707031; Valencia Workshop Proceedings, hep-ph/9711438 Phys Rev D60 (1999) 013005 hep-ph/9807277 Phys Rev D? (2000) hep-ph/9909321
Notes:
We study the llqq final state in e+e- collisions at LEP2. The analysis covers all ranges of fermion pair invariant mass. Numbers of observed e+e-qq events and kinematic distributions are compared to Standard Model Monte Carlo samples.
Authors:The OPAL collaboration
Proposed speaker:
Contact person:David J Miller
(CERN),
dave.miller@cern.ch
Sessions: PA-11 Search for New Particles and New Phenomena / PL-07a Search for New Particles and New Phenomena (Results from e+e- Colliders)
Supporting papers: OPAL Physics Note PN428 = http://opal.web.cern.ch/Opal/pubs/physnote/html/pn428.html
Notes:
We present preliminary results of searches for technirho, techniomega, and Z' particles, using their decay into e+e-. The search is based on 120.9 pb**-1 of data collected by the DZero detector at the Tevatron during 1992-1996. In the absence of a signal we set 95% CL upper limits on the production cross section and decay into e+e- as a function of the mass of the decaying particle. For certain model parameters, we exclude the existence of degenerate technirho and technomega states with masses below 210 GeV/c**2. We exclude a Z' with mass below 680 GeV/c**2, assuming that the Z' has the same couplings as the Z boson.
Authors:The DZero Collaboration
Proposed speaker: To be decided by the DZero Collaboration
Contact person:Bernard G. Pope
(Michigan State University),
pope@pa.msu.edu
Sessions: PA-11 Search for New Particles and New Phenomena /
Supporting papers:
Notes:
The Tevatron is expected to be most sensitive to the Standard Model Higgs in its associated production with a W or Z boson. CDF has performed individual searches for such production in each decay channel of the vector boson, assuming that the Higgs decays to b bbar. These searches use data collected by the Collider Detector at Fermilab (CDF) during the 1992-93 and 1994-95 runs (Run I). The individual results are reviewed, and a combined cross section limit is presented.
Authors:CDF Collaboration
Proposed speaker: Krzysztof Sliwa
Contact person:Krzysztof J Sliwa
(Tufts University),
sliwa@tuhep9.phy.tufts.edu
Sessions: PA-11 Search for New Particles and New Phenomena / PL-07b Search for New Particles and New Phenomena (Results from Hadron Colliders)
Supporting papers:
Notes:
We present recent results of searches for supersymmetry (SUSY) in ppbar collisions at sqrt s = 1.8 TeV. These searches use data collected by the Collider Detector at Fermilab (CDF) during the 1992-93 and 1994-95 runs (Run I). Both R-parity conserving and R-parity violating scenarios are examined in the frameworks of the MSSM and mSUGRA. Given the excellent lepton identification and b-tagging capabilities of CDF, these searches are highly sensitive to SUSY signatures.
Authors:CDF Collaboration
Proposed speaker: Tom LeCompte
Contact person:Tom J LeCompte
(Argonne),
lecompte@fnal.gov
Sessions: PA-11 Search for New Particles and New Phenomena / PL-07b Search for New Particles and New Phenomena (Results from Hadron Colliders)
Supporting papers:
Notes:
During April 2000, the x-ray binary Cygnus X-3 emitted its largest flare since January 1991. During that earlier flare, the Soudan 2 detector reported an excess of muons from the direction of this object correlated with the onset of this flare. Here we report on Soudan 2 muon observation during April 2000 and compare the data with earlier observations.
Authors:Soudan 2 Collaboration
Proposed speaker: M. L. Marshak
Contact person:Marvin L Marshak
(University of Minnesota),
marshak@umn.edu
Sessions: PA-11 Search for New Particles and New Phenomena / PL-16a Experimental Particle Astrophysics (High Energy Particles from the Universe)
Supporting papers:
Notes:
In the s-channel Higgs-exchange processes, the interference between the amplitudes for scalar and pseudoscalar Higgs is sizable, if the helicities of initial and final particles are properly fixed and if the mass difference between these bosons is not much larger than their decay widths. We discuss this interference effect in the process \mu^+ \mu^- -> t t-bar. Examining the effects gives us information on CP-parity for Higgs bosons and on the sign of a product of the coupling constants for Higgs-fermions vertices. The feasibility of observing the effect in future muon colliders is evaluated in MSSM.
Authors:Eri Asakawa, Akio Sugamoto and Isamu Watanabe
Proposed speaker: Eri Asakawa
Contact person:Eri Asakawa
(Ochanomizu Univ.),
g9870401@edu.cc.ocha.ac.jp
Sessions: PA-11 Search for New Particles and New Phenomena / PL-14 Future Accelerators
Supporting papers: hep-ph/0004005 (to appear in Euro. Phys. J. C.); "Production of Scalar Higgs and Pseudoscalar Higgs in Multi-Higgs Doublet Models at gamma gamma colliders", E.A., J.Kamoshita, A.Sugamoto, I.Watanabe, hep-ph/9912373(to be published in Euro.Phys.J.C.);
Notes:Now the extended work to Higgs bosons with no definite CP-parity is almost completed by E.A, S.Y.Choi, J.S.Lee. I am going to mention also this topic in my talk.
We study the single production of first generation leptoquarks in association with a $e^\pm$ at the Fermilab Tevatron. We focus our attention on final states exhibiting a $e^+e^-$ pair and jets, and perform a detailed analyses of signal and backgrounds. The single leptoquark production cross section depends on the leptoquark Yukawa coupling to lepton-quark pairs and we show that the study of this mode can extend considerably the leptoquark search for a large range of these couplings. In fact, for Yukawa couplings of the electromagnetic strength, the combined results of the Tevatron experiments can exclude the existence of leptoquarks with masses up to 260--285 (370--425) GeV at the RUN I (RUN II), depending on their type.
Authors:O.J.P. \'Eboli and T.L. Lungov
Proposed speaker: O.J.P. \'Eboli
Contact person:Oscar JP Eboli
(Instituto de Fisica Teorica da UNESP),
eboli@ift.unesp.br
Sessions: PA-11 Search for New Particles and New Phenomena / PL-07b Search for New Particles and New Phenomena (Results from Hadron Colliders)
Supporting papers: hep-ph/9911292, to appear in Phys. Rev D
Notes:
The existence of extra chiral generations with all fermions heavier than $M_Z$ is strongly disfavoured by the precision electroweak data. However the data are fitted nicely even by a few extra generations, if one allows neutral leptons to have masses close to $50$ GeV. The data allow inclusion of one additional generation of heavy fermions in SUSY extension of Standard Model if chargino and neutralino have masses close to $60$ GeV with $\Delta m \simeq 1$ GeV. The latest electroweak precision results from LEP, SLC and Fermilab are used to bound extra generations.
Authors:M.Maltoni, V.A.Novikov, L.B.Okun, A.N.Rozanov, M.I.Vysotsky
Proposed speaker: A.Rozanov
Contact person:Alexandre N. ROZANOV
(Centre de Physique des Particules de Marseille (CPPM)),
rozanov@cppm.in2p3.fr
Sessions: PA-11 Search for New Particles and New Phenomena / PL-07a Search for New Particles and New Phenomena (Results from e+e- Colliders)
Supporting papers: Follow-up of the paper accepted in PL
Notes:New electroweak precision data will be used to update the numerical results before Osaka conference.
We present recent results of searches for Technicolor Particles (TC) and Large Extra Spacetime Dimensions in ppbar collisions at sqrt s = 1.8 TeV. These searches use data collected by the Collider Detector at Fermilab (CDF) during the 1992-93 and 1994-95 runs (Run I). The good lepton identification and b-tagging capabilities make the searches sensitive to TC particle signatures. The dilepton channel is used for the Extra Dimensions search. Run II prospects are also discussed.
Authors:The CDF collaboration
Proposed speaker: Kaori Maeshima
Contact person:Kaori Maeshima
(Fermilab),
maeshima@fnal.gov
Sessions: PA-11 Search for New Particles and New Phenomena / PL-07b Search for New Particles and New Phenomena (Results from Hadron Colliders)
Supporting papers: Search for Second and Third Generation Leptoquarks Including Production via Technicolor Interactions in p anti-p Collisions at s**(1/2) = 1.8 TeV T. Affolder et al., The CDF Collaboration, FERMILAB-PUB-00/073-E, submitted to Phys. Rev. Lett. March 31, 2000. Search for Color Singlet Technicolor Particles in p anti-p Collisions at s**(1/2) = 1.8 TeV T. Affolder, The CDF Collaboration, Phys. Rev. Lett. 84, 1110 (2000). Search for a Technicolor omega(t) Particle in Events with a Photon and a b-quark Jet at CDF F. Abe et al., The CDF Collaboration, Phys. Rev. Lett. 83, 3124 (1999).
Notes:My (Kaori Maeshima, proposed speaker) trip is not approved yet, and there is only a small chance I could attend the conference. In any cases, hopefully, someone from CDF could present this talk.
We study the potential of CERN Large Hadron Collider (LHC) to unravel the existence of invisibly decaying Higgs bosons, predicted in a wide class of models. We analyze in detail the signal and backgrounds for such a Higgs boson produced via vector boson fusion. We choose appropriate cuts to enhance the sensitivity to the Higgs invisible decay mode. Our results demonstrate that LHC is capable of discovering such a Higgs boson for a wide range of masses and invisible branching ratios. In particular, for an intermediate mass Higgs boson, the signal can be observed for Higgs invisible branching ratios as low as 10%.
Authors:O.J.P. \'Eboli and D. Zeppenfeld
Proposed speaker: O.J.P. \'Eboli
Contact person:Oscar JP Eboli
(Instituto de Fisica Teorica - UNESP),
eboli@ift.unesp.br
Sessions: PA-11 Search for New Particles and New Phenomena / PL-07b Search for New Particles and New Phenomena (Results from Hadron Colliders)
Supporting papers:
Notes:
Deep inelastic ep scattering data is used to search for eq contact interactions at scales not directly accessible at HERA. In a combined analysis of e^+p and e^-p data limits on new phenomena are derived. For conventional contact interactions lower bounds are set on compositeness scales Lambda^+- at 1.5 - 6.4 TeV and on leptoquark exchange for ratios of mass/coupling of order 1 TeV. A search for gravitational effects through the exchange of Kaluza-Klein excitations of gravitons which propagate into large extra dimensions results in lower limits on the effective Planck scale M S around 0.7 TeV.
Authors:H1 Collaboration
Proposed speaker: An H1 Speaker
Contact person:Peter Schleper
(DESY),
Peter.Schleper@desy.de
Sessions: PA-11 Search for New Particles and New Phenomena / PL-07b Search for New Particles and New Phenomena (Results from Hadron Colliders)
Supporting papers:
Notes: (050)-952
A search for new bosons possessing couplings to lepton-quark pairs is performed by the H1 experiment at HERA using ~80 pb^-1 of e^+ p data collected from 1994 to 2000. About half of this data was recently collected at a centre of mass energy of ~320 GeV providing an enhanced sensitivity to leptoquarks at large masses. First generation leptoquarks are searched for in very high Q^2 deep-inelastic scattering and the measurements are compared to Standard Model expectations. In addition, leptoquarks possessing couplings to mixed fermion generations, which could lead to signals of lepton flavor violation, are searched for in events with a high transverse momentum muon or tau.
Authors:H1 Collaboration
Proposed speaker: An H1 Speaker
Contact person:Peter Schleper
(DESY),
Peter.Schleper@desy.de
Sessions: PA-11 Search for New Particles and New Phenomena / PL-07b Search for New Particles and New Phenomena (Results from Hadron Colliders)
Supporting papers:
Notes: (052)
A search for scalar and vector leptoquarks coupling to first generation fermions is performed by the H1 experiment in e^- p collisions at HERA using 14.4 pb^-1 of data collected in 1998-99 at a centre of mass energy of ~ 320 GeV. No evidence for the direct production of leptoquarks is found in an analysis of neutral current deep-inelastic scattering data and exclusion limits are derived. For a Yukawa coupling of electromagnetic strength, leptoquarks with fermionic number F=0 are excluded for masses up to ~290 GeV. This analysis complements the leptoquark searches previously performed with e^+p data at HERA and which was most sensitive to F=2 leptoquarks.
Authors:H1 Collaboration
Proposed speaker: An H1 Speaker
Contact person:Peter Schleper
(DESY),
Peter.Schleper@desy.de
Sessions: PA-11 Search for New Particles and New Phenomena / PL-07b Search for New Particles and New Phenomena (Results from Hadron Colliders)
Supporting papers:
Notes: (053)
A search for excited fermions f^* of the first generation in e^+ p scattering at HERA is presented using H1 data with an integrated luminosity of ~37 pb^-1. All electroweak decays of excited fermions, f^* -> f gamma (f Z, f W) are considered and all possible decays of the Z and W bosons into either hadrons, neutrinos or charged leptons of the first two generations are taken into account. No evidence for f^* production is found. Mass dependent exclusion limits on cross sections and on the ratio of coupling constants over compositeness scale are derived.
Authors:H1 Collaboration
Proposed speaker: An H1 Speaker
Contact person:Peter Schleper
(DESY),
Peter.Schleper@desy.de
Sessions: PA-11 Search for New Particles and New Phenomena / PL-07b Search for New Particles and New Phenomena (Results from Hadron Colliders)
Supporting papers:
Notes: (054)
Excited neutrinos nu^* of the first generation are searched for in e^- p collisions at a centre of mass energy of ~320 GeV using data collected by the H1 experiment in 1998 and 1999, corresponding to an integrated luminosity of ~15 pb^-1. The nu^* signal is sought in the decay channels nu^* -> nu gamma as well as nu^* -> e W followed by a hadronic decay of the weak boson. No evidence for nu^* production is found. Mass dependent exclusion limits on cross sections and on the ratio of coupling constants over compositeness scale are derived. The e^- p data allows to considerably improve the previously existing bounds from H1 on \nu^* production which had been obtained using e^+ p data.
Authors:H1 Collaboration
Proposed speaker: An H1 Speaker
Contact person:Peter Schleper
(DESY),
Peter.Schleper@desy.de
Sessions: PA-11 Search for New Particles and New Phenomena / PL-07b Search for New Particles and New Phenomena (Results from Hadron Colliders)
Supporting papers:
Notes: (055)
A search for squarks of R-parity violating (Rpv) supersymmetry is performed in ep collisions at HERA using H1 data taken between 1994 and 1997 corresponding to an integrated luminosity of 37 pb^-1. Direct single production of squarks of each generation by e^+-quark fusion via a Yukawa coupling lambda' is considered and all possible squarks decays, Rpv decays and gauge decays into a neutralino or a chargino, are taken into account. No evidence for a signal is found in the various Rpv and gauge decay channels analysed and mass dependent upper limits on the Rpv Yukawa coupling are derived. A study of the dependence of the obtained sensitivity on the free parameters of the Minimal Supersymmetric Standard Model is also presented.
Authors:H1 Collaboration
Proposed speaker: An H1 Speaker
Contact person:Peter Schleper
(DESY),
Peter.Schleper@desy.de
Sessions: PA-11 Search for New Particles and New Phenomena / PL-07b Search for New Particles and New Phenomena (Results from Hadron Colliders)
Supporting papers:
Notes: (056)
A search for the resonant production of a light R-parity violating (Rpv) stop squark is performed by the H1 experiment at HERA using e^+ p data collected between 1994 and 1997 and corresponding to an integrated luminosity of ~37 pb^-1. The analysis considers the stop decay to a real sbottom and a W boson. Assuming that the lightest sbottom mass eigenstate is the lightest supersymmetric particle, it only decays via Rpv into a neutrino and a down quark. Final states resulting from the leptonic (e+nu e or muon+nu muon) or hadronic decay of the W have been considered, and upper limits on the cross section of the associated production of the sbottom with a W boson have been derived. The interpretation of these bounds in terms of constraints on the free parameters of the Minimal Supersymmetric Standard Model is also presented.
Authors:H1 Collaboration
Proposed speaker: An H1 Speaker
Contact person:Peter Schleper
(DESY),
Peter.Schleper@desy.de
Sessions: PA-11 Search for New Particles and New Phenomena / PL-07b Search for New Particles and New Phenomena (Results from Hadron Colliders)
Supporting papers:
Notes: (057)
A search for single top production via flavour changing neutral currents (FCNC) in the reaction e u (c) -> e t is performed in the H1 experiment at the ep collider HERA. The analysis uses e^+ p and e^- p data collected between 1994 and 1999, corresponding to integrated luminosities of ~37 pb^-1 and ~14 pb^*-1 respectively. Upper limits on the cross section for the process e p -> e + t + X are obtained. Using an effective Lagrangian to parameterize FCNC top interactions, these bounds are interpreted as upper limits on the anomalous magnetic coupling kappa gamma of the photon to a top and a light quark, and are compared to those obtained by other experiments.
Authors:H1 Collaboration
Proposed speaker: An H1 Speaker
Contact person:Peter Schleper
(DESY),
Peter.Schleper@desy.de
Sessions: PA-11 Search for New Particles and New Phenomena / PL-07b Search for New Particles and New Phenomena (Results from Hadron Colliders)
Supporting papers:
Notes: (060)
A search is performed for events with an imbalance in transverse momentum and with an isolated high energy lepton in e^-p and e^+p scattering data collected in the 1998-2000 HERA runs. The analysis is motivated by the result of a similar search performed in the 1994-97 e^+p data, where one e^- and five muon events were found showing evidence for unseen particles carrying transverse momentum. Three of these events have kinematic properties atypical for the expected Standard Model background, which is dominated by W^+- production with subsequent leptonic decays.
Authors:H1 Collaboration
Proposed speaker: An H1 Speaker
Contact person:Peter Schleper
(DESY),
Peter.Schleper@desy.de
Sessions: PA-11 Search for New Particles and New Phenomena / PL-07b Search for New Particles and New Phenomena (Results from Hadron Colliders)
Supporting papers:
Notes: (075)-974
The cross sections of 2 and 3-jet production at high transverse momentum, P T, in photoproduction at HERA are presented for both e^+p and e^-p data. The cross sections, measured as a function of P T and of the 2 and 3 jet invariant mass up to the highest values accessible at HERA, are compared with the expectations of next to leading order QCD.
Authors:H1 Collaboration
Proposed speaker: An H1 Speaker
Contact person:Peter Schleper
(DESY),
Peter.Schleper@desy.de
Sessions: PA-11 Search for New Particles and New Phenomena / PL-07b Search for New Particles and New Phenomena (Results from Hadron Colliders)
Supporting papers:
Notes: (077) 5/17/00 TK/TY-Above sessoins are the 2nd choice. Same as #977.
Jet production in charged and neutral current events in the kinematic range of Q^2 from 640 to 25000 GeV^2 is studied in deep-inelastic scattering at HERA. The distributions of jet polar angle, transverse energy, jet resolution, dijet mass, and other dijet variables are determined. The measured jet distributions in charged and neutral current scattering are described by perturbative QCD calculations in next-to-leading order. A direct, model independent comparison of the jet distributions in charged and neutral current events, selected in the same kinematic range, is performed. The jet distributions in both processes are found to be compatible thus testing the independence of QCD dynamics of the electroweak scattering process.
Authors:H1 Collaboration
Proposed speaker: An H1 Speaker
Contact person:Peter Schleper
(DESY),
Peter.Schleper@desy.de
Sessions: PA-11 Search for New Particles and New Phenomena / PL-07b Search for New Particles and New Phenomena (Results from Hadron Colliders)
Supporting papers:
Notes: (092) 5/17/00 TY/TK - Above sessions are the 2nd choice. Same as #994 for PA-03/PL-11.
Three-jet cross sections have been measured for the first time in deep-inelastic e-p-scattering at HERA for photon virtualities 5 < Q^2 < 5000 GeV^2 using the inclusive k t jet algorithm in the Breit frame. The data are presented as function of Q^2, the Bjorken scaling variable x Bj, the mean transverse energy of the jets in the Breit frame and the jet invariant mass M jj. Moreover, in the three-jet center of mass frame the shape of the jet energy fractions and two angles characterising the 3-jet matrix element have been studied. The data are compared to alpha s^2 pQCD-calculations.
Authors:H1 Collaboration
Proposed speaker: An H1 Speaker
Contact person:Peter Schleper
(DESY),
Peter.Schleper@desy.de
Sessions: PA-11 Search for New Particles and New Phenomena / PL-07b Search for New Particles and New Phenomena (Results from Hadron Colliders)
Supporting papers:
Notes: (097) 5/17/00 TK/TY-Above sessoins are the 2nd choice. Same as #995.
The reaction e+p->e+X is studied with the H1 detector at Hera. The data cover momentum transfers Q^2 between 200 GeV^2 and 30,000 GeV^2 and correspond to an integrated luminosity of 35.6 pb^(-1). The differential cross section dsigma/dQ^2 is compared to the Standard Model expectation for neutral current scattering and analysed to search for bar(e)e bar(q)q contact interactions. No evidence for new phenomena is observed. The results are used to set limits on scales within models of electron-quark compositeness, quark form factors and the exchange of virtual heavy leptoquarks. A search for gravitational effects mediated through the exchange of virtual gravitons which propagate into large extra dimensions is presented.
Authors:H1 Collaboration
Proposed speaker: An H1 Speaker
Contact person:Peter Schleper
(DESY),
Peter.Schleper@desy.de
Sessions: PA-11 Search for New Particles and New Phenomena / PL-07b Search for New Particles and New Phenomena (Results from Hadron Colliders)
Supporting papers:
Notes:see hep-ex/0003002 (104)-1002
In 1999 the four experiments have collected data at energies between 192 and 202 GeV, for approximately 900 pb-1 integrated luminosity. The LEP working group for Higgs boson searches has combined these data with data sets collected earlier at lower energies. No statistically significant excess has been observed when compared to the Standard Model background prediction. The following 95% confidence level bounds have been obtained. For the Standard Model Higgs boson, the lower bound on the mass is 107.9 GeV/c2. In the Minimal Supersymmetric Standard Model and from representative scans of the SUSY parameters, the mass limits mh>88.3 GeV/c2 and mA>88.4 GeV/c2 are obtained for the light CP-even and the CP-odd neutral Higgs boson, respectively. Furthermore, for a top quark mass less than or equal to 174.3 GeV/c2, and assuming no (or large) mixing in the scalar-top sector, the range 0.4<tan-beta<4.1 (0.7<tan-beta<1.8) is excluded. Finally, for charged Higgs bosons predicted by two-doublet extensions of the Standard Model and decaying only into the channels H+ -> c-sbar and tau+ nu, a lower bound of 78.6 GeV/c2 is obtained for the mass.
Authors: ALEPH, DELPHI, L3 and OPAL Collaborations The LEP working group for Higgs boson searches
Proposed speaker:
Contact person:Peter Igo-Kemenes
(CERN),
Peter.Igo-Kemenes@cern.ch
Sessions: PA-11 Search for New Particles and New Phenomena / PL-07a Search for New Particles and New Phenomena (Results from e+e- Colliders)
Supporting papers: CERN-EP-2000-055 = http://lephiggs.web.cern.ch/LEPHIGGS/papers/CERN-EP-2000-055/index.html
Notes:
The LEP working group for Higgs boson searches has combined the data collected by the four collaborations during the recent runs of the year 2000 and has produced new, preliminary, experimental search results for neutral and charged Higgs bosons.
Authors: ALEPH, DELPHI, L3 and OPAL Collaborations The LEP working group for Higgs boson searches
Proposed speaker:
Contact person:Peter Igo-Kemenes
(CERN),
Peter.Igo-Kemenes@cern.ch
Sessions: PA-11 Search for New Particles and New Phenomena / PL-07a Search for New Particles and New Phenomena (Results from e+e- Colliders)
Supporting papers: To be available one week before the conference
Notes:
Various eeqq vector contact-interaction models have been tested using the combined sample of high-Q^2 e^+p and e^-p neutral current deep inelastic scattering data collected with the ZEUS detector at HERA. The e^+p data taken in 1994-97 at 300 GeV centre-of-mass energy correspond to an integrated luminosity of 47.7 pb^-1. The 16 pb^-1 of e^-p data collected in 1998-99 at a centre-of-mass energy of 318 GeV were also used to improve significantly the limits on the effective mass scales Lambda for most of the models.
Authors:ZEUS Collaboration
Proposed speaker:
Contact person:Stefan Schlenstedt
(DESY),
stefan.schlenstedt@ifh.de
Sessions: PA-11 Search for New Particles and New Phenomena / PL-07b Search for New Particles and New Phenomena (Results from Hadron Colliders)
Supporting papers:
Notes:
Resonances in the e^+ jet invariant-mass spectrum from the reaction e^+ p -> e^+ X at a centre-of-mass energy of 318 GeV have been sought using the ZEUS detector at HERA. The data were collected from June 1999 to summer 2000 and correspond to an integrated luminosity of about 34 pb^-1. Comparison is made with previous results from the 1994-97 data sample with a centre-of-mass energy of 300 GeV.
Authors:ZEUS Collaboration
Proposed speaker:
Contact person:Stefan Schlenstedt
(DESY),
stefan.schlenstedt@ifh.de
Sessions: PA-11 Search for New Particles and New Phenomena / PL-07b Search for New Particles and New Phenomena (Results from Hadron Colliders)
Supporting papers:
Notes:
Events of the type e^+p -> l X, where l is a final-state higher-generation lepton (\mu or \tau) of high transverse momentum, have been sought at a centre-of-mass energy of 300 GeV with the ZEUS detector at HERA using an integrated luminosity of 47.7 pb^-1. No evidence was found for lepton-flavour violation. Constraints are set on the couplings of leptoquarks (LQs) mediating lepton-flavour-violating ep reactions. Limits are provided for the \tau decay channel for LQ masses below sqrt(s) and for both the \mu and \tau channels for LQ masses much greater than sqrt(s).
Authors:ZEUS Collaboration
Proposed speaker:
Contact person:Stefan Schlenstedt
(DESY),
stefan.schlenstedt@ifh.de
Sessions: PA-11 Search for New Particles and New Phenomena / PL-07b Search for New Particles and New Phenomena (Results from Hadron Colliders)
Supporting papers:
Notes:
Heavy excited states of electrons and quarks have been searched for in e^+p collisions at a centre-of-mass energy of 300 GeV with the ZEUS detector at HERA using an integrated luminosity of 47.7 pb^-1. Excited neutrinos have been sought in e^-p collisions at a centre-of-mass energy of 318 GeV using an integrated luminosity of 16 pb^-1. No evidence for any such states was found and limits were placed on the characteristic couplings.
Authors:ZEUS Collaboration
Proposed speaker:
Contact person:Stefan Schlenstedt
(DESY),
stefan.schlenstedt@ifh.de
Sessions: PA-11 Search for New Particles and New Phenomena / PL-07b Search for New Particles and New Phenomena (Results from Hadron Colliders)
Supporting papers:
Notes:
A search for events containing high-transverse-momentum isolated tracks with large missing transverse momentum has been performed with the ZEUS detector at HERA using 82 pb^-1 of integrated luminosity collected during the period 1994-1999. The number of observed events, seven e^\pm and four muons, is consistent with the expections from Standard Model processes. The kinematic variables of the events lie in the region predicted by the Standard Model. The excess of such events reported by the H1 collaboration is therefore not confirmed by the ZEUS data.
Authors:ZEUS Collaboration
Proposed speaker:
Contact person:Stefan Schlenstedt
(DESY),
stefan.schlenstedt@ifh.de
Sessions: PA-11 Search for New Particles and New Phenomena / PL-07b Search for New Particles and New Phenomena (Results from Hadron Colliders)
Supporting papers:
Notes:
Squarks produced via an R-parity violating interaction in e^+p collisions at a centre-of-mass energy of 300 GeV have been sought with the ZEUS detector at HERA. Squarks produced in e^+ quark fusion could decay to e-quark or gaugino-quark via a supersymmetric gauge decay, resulting in a final state with multiple jets and a lepton that could be a neutrino, e^+ or e^-. No evidence for squark production was found and limits were set on the R-parity violating coupling as a function of the squark mass and the SUSY parameters \mu and M_2.
Authors:ZEUS Collaboration
Proposed speaker:
Contact person:Stefan Schlenstedt
(DESY),
stefan.schlenstedt@ifh.de
Sessions: PA-11 Search for New Particles and New Phenomena / PL-07b Search for New Particles and New Phenomena (Results from Hadron Colliders)
Supporting papers:
Notes:
A study of the \nu(bar)-jet mass spectrum in e^+p -> \nu(bar) X events at centre-of-mass energy 300 GeV has been performed with the ZEUS detector at HERA using an integrated luminosity of 47.7 pb^-1. The mass spectrum is in good agreement with the Standard Model; no significant excess attributable to a narrow resonance is observed. By using both e^+p -> e^+X and e^+p -> \nu(bar) X data, mass-dependent limits are set on s-channel production of scalar and vector resonant states and constraints placed on the production of leptoquarks and R-parity-violating squarks.
Authors:ZEUS Collaboration
Proposed speaker:
Contact person:Stefan Schlenstedt
(DESY),
stefan.schlenstedt@ifh.de
Sessions: PA-11 Search for New Particles and New Phenomena / PL-07b Search for New Particles and New Phenomena (Results from Hadron Colliders)
Supporting papers:
Notes:
The e^+ jet invariant mass spectrum produced in the reaction e^+p->e^+X has been studied at a center-of-mass energy of 300 GeV with the ZEUS detector at HERA using an integrated luminosity of 47.7 pb^-1. The observed mass spectrum agrees with the Standard Model up to 210 GeV. Above this mass, some excess is seen, which is however consistent with originating from high-Q^2 neutral current events. Limits are presented for leptoquark or R-parity-violating squark production. Specific leptoquark types are ruled out at 95% C.L. for coupling strength \lambda =0.3 for masses between 150 and 280 GeV.
Authors:ZEUS Collaboration
Proposed speaker:
Contact person:Stefan Schlenstedt
(DESY),
stefan.schlenstedt@ifh.de
Sessions: PA-11 Search for New Particles and New Phenomena / PL-07b Search for New Particles and New Phenomena (Results from Hadron Colliders)
Supporting papers:
Notes:
The ATLAS experiment at the LHC will be able to look for a Standard Model Higgs boson over the full range of allowed masses and to fully explore the parameter space of the Minimal Supersymmetric extension of the Standard Model (MSSM). This potential has been reassessed recently with the final detector layout, as described in recent Technical Design Reports. In this talk the expected ATLAS potential for the discovery of Standard Model and Supersymmetric Higgs bosons is presented. The study of the MSSM Higgs sector includes also cases where Higgs bosons decay into SUSY particles or appear in decays of these particles. It is also discussed how accurately Higgs boson parameters can be measured at the LHC.
Authors:ATLAS Collaboration
Proposed speaker:
Contact person:Fabiola Gianotti
(CERN),
fabiola.gianotti@cern.ch
Sessions: PA-11 Search for New Particles and New Phenomena /
Supporting papers:
Notes:
Due to the high energy and luminosity of the machine, the LHC experiments have a huge discovery potential for New Physics. Squarks and gluinos can be discovered up to masses of ~2.5 TeV and several precise measurements can be performed in the SUSY sector. Quark compositeness can be searched for up to scales of 40 TeV. Other particles predicted by New Physics (e.g. excited quarks and leptons, leptoquarks, additional gauge bosons) should be discovered up to masses of about 5 TeV. This talk will highlight the most recent studies performed by ATLAS in the context of work for the ``Detector and Physics Performance'' Technical Design Report and of recent LHC workshops.
Authors:ATLAS Collaboration
Proposed speaker:
Contact person:Fabiola Gianotti
(CERN),
fabiola.gianotti@cern.ch
Sessions: PA-11 Search for New Particles and New Phenomena /
Supporting papers:
Notes:
Results from a search for long-lived, heavy neutral particles using an instrumented decay detector combined with the NuTeV neutrino detector will be presented.
Authors:NuTeV Collaboration
Proposed speaker: Michael Shaevitz
Contact person:Michael Shaevitz
(Fermilab/Columbia Univ.),
shaevitz@fnal.gov
Sessions: PA-11 Search for New Particles and New Phenomena /
Supporting papers:
Notes:6/7/00 TY-No abstract, but was in the program. 7/15/00 TY-Entered abstract sent by E-mail on 7/14.
Authors:John F. Gunion
Proposed speaker: John F. Gunion
Contact person:John F. Gunion
(UC Davis),
gunion@physics.ucdavis.edu
Sessions: PA-11 Search for New Particles and New Phenomena /
Supporting papers:
Notes:6/7/00 TY-No abstract, but was in the program.
End of abstracts for PA-11 Search for New Particles and New Phenomena