We perform an investigation of the WW -> WW process for the LHC within the framework of the electroweak chiral lagrangian. The physics has been implemented in the HERWIG monte carlo programme which allows a study at the hadron level.
Authors:J R Forshaw, B E Cox and A New
Proposed speaker: J R Forshaw
Contact person:Jeff R Forshaw
(University of Manchester),
forshaw@mail.cern.ch
Sessions: PA-05 Tests of the Electroweak Gauge Theory / PL-09 Beyond the Standard Model
Supporting papers:
Notes:
The fraction of Z to bbbar events in hadronic Z decays has been measured by the OPAL experiment using the data collected at LEP between 1992 and 1995. The Z to bbbar decays were tagged using displaced secondary vertices, and high momentum electrons and muons. Systematic uncertainties were reduced by measuring the b-tagging efficiency using a double tagging technique. Efficiency correlations between opposite hemispheres of an event are small, and are well understood through comparisons between real and simulated data samples. A value of Rb = 0.2178 +- 0.0011 +- 0.0013 was obtained, where the first error is statistical and the second systematic. The uncertainty on Rc, the fraction of Z to ccbar events in hadronic Z decays, is not included in the errors. The dependence on Rc is Delta(Rb)/Rb = -0.056*Delta(Rc)/Rc where Delta(Rc) is the deviation of Rc from the value 0.172 predicted by the Standard Model. The result for Rb agrees with the value of 0.2155 +- 0.0003 predicted by the Standard Model.
Authors:The OPAL collaboration
Proposed speaker:
Contact person:David J Miller
(CERN),
dave.miller@cern.ch
Sessions: PA-05 Tests of the Electroweak Gauge Theory / PL-06a Precision Tests of the Standard Model (Electroweak Gauge Theory (W, Z, Top, etc.)
Supporting papers: CERN-EP/98-137, Eur. Phys. J. C8 (1999) 217-239 =http://opal.web.cern.ch/Opal/pubs/paper/html/pr257.html
Notes:Also of interest to Parallel session 7, Heavy Flavour; Plenary session 3, Heavy Flavour
A study of W-pair production in e+e- annihilations at LEP2 is presented, based on 877 W+W- candidates corresponding to an integrated luminosity of 57 pb-1 at sqrt(s) = 183 GeV. Assuming that the angular distributions of the W-pair production and decay, as well as their branching fractions, are described by the Standard Model, the W-pair production cross-section is measured to be 15.43 +- 0.61 (stat.) +- 0.26 (syst.) pb. Assuming lepton universality and combining with our results from lower centre-of-mass energies, the W branching fraction to hadrons is determined to be 67.9 +- 1.2 (stat.) +- 0.5 (syst.)%. The number of W-pair candidates and the angular distributions for each final state (qqlnu,qqqq,lnulnu) are used to determine the triple gauge boson couplings. After combining these values with our results from lower centre-of-mass energies we obtain D(kappa_g)=0.11+0.52-0.37, D(g^z_1)=0.01+0.13-0.12 and lambda=-0.10+0.13-0.12, where the errors include both statistical and systematic uncertainties and each coupling is determined setting the other two couplings to the Standard Model value. The fraction of W bosons produced with a longitudinal polarisation is measured to be 0.242+-0.091(stat.)+-0.023(syst.). All these measurements are consistent with the Standard Model expectations.
Authors:The OPAL collaboration
Proposed speaker:
Contact person:David J Miller
(CERN),
dave.miller@cern.ch
Sessions: PA-05 Tests of the Electroweak Gauge Theory / PL-06a Precision Tests of the Standard Model (Electroweak Gauge Theory (W, Z, Top, etc.)
Supporting papers: CERN-EP/98-167, Eur. Phys. J. C8 (1999) 191-215 =http://opal.web.cern.ch/Opal/pubs/paper/html/pr260.html
Notes:
Bose-Einstein correlations between like-charge pions are studied in hadronic final states produced by e+e- annihilations at center-of-mass energies of 172 and 183 GeV. Three event samples are studied, each dominated by one of the processes W+W- to qqlnu, W+W- to qqqq, or (Z/g)* to qq. After demonstrating the existence of Bose-Einstein correlations in W decays, an attempt is made to determine Bose-Einstein correlations for pions originating from the same W boson and from different W bosons, as well as for pions from (Z/g)* to qq events. Results are obtained for the individual chaoticity parameters lambda assuming a common source radius R.
Authors:The OPAL collaboration
Proposed speaker:
Contact person:David J Miller
(CERN),
dave.miller@cern.ch
Sessions: PA-05 Tests of the Electroweak Gauge Theory / PL-06a Precision Tests of the Standard Model (Electroweak Gauge Theory (W, Z, Top, etc.)
Supporting papers: CERN-EP/98-174, Eur. Phys. J. C8 (1999) 559-571 =http://opal.web.cern.ch/Opal/pubs/paper/html/pr262.html
Notes:
Using a data sample of 57 pb-1 recorded at a centre-of-mass energy of 183 GeV with the Opal detector at LEP, 282 W+W- -> qqqq and 300 W+W- -> qqlnu candidate events are used to obtain a measurement of the mass of the W boson, W_W = 80.39 +- 0.13(stat.) +- 0.05(syst.) GeV assuming the Standard Model relation between M_W and Gam_W. A second fit provides a direct measure of the width of the W boson and gives Gam_W = 1.96 +- 0.34(stat.) +- 0.20(syst.) GeV. These results are combined with previous OPAL results to obtain M_W = 80.38 +- 0.12(stat.) +- 0.05(syst.) GeV and Gam_W = 1.84 +- 0.32(stat.) +- 0.20(syst.) GeV.
Authors:The OPAL collaboration
Proposed speaker:
Contact person:David J Miller
(CERN),
dave.miller@cern.ch
Sessions: PA-05 Tests of the Electroweak Gauge Theory / PL-06a Precision Tests of the Standard Model (Electroweak Gauge Theory (W, Z, Top, etc.)
Supporting papers: CERN-EP/98-197, Phys. Lett. B453 (1999) 138-152 =http://opal.web.cern.ch/Opal/pubs/paper/html/pr268.html
Notes:
A study of W+W- events accompanied by hard photon radiation produced in e+e- collisions at LEP is presented. Events consistent with two on-shell W-bosons and an isolated photon are selected from 183pb^-1 of data recorded at root{s}=189GeV. From these data, 17 W+W-gamma candidates are selected with photon energy greater than 10GeV, consistent with the Standard Model expectation. These events are used to measure the e+e- to W+W-gamma cross-section within a set of geometric and kinematic cuts; sigma{W+W-gamma} = 136+-37+-8 fb, where the first error is statistical and the second systematic. The photon energy spectrum is used to set the first direct, albeit weak, limits on possible anomalous contributions to the {W+ W- gamma gamma} and {W+ W- gamma Z0} vertices: -0.070GeV^{-2} < a_0/Lambda^2 < 0.070GeV^{-2}, -0.13GeV^{-2} < a_c/Lambda^2 < 0.19GeV^{-2}, -0.61GeV^{-2} < a_n/Lambda^2 < 0.57GeV^{-2}, where Lambda represents the energy scale for new physics.
Authors:The OPAL collaboration
Proposed speaker:
Contact person:David J Miller
(CERN),
dave.miller@cern.ch
Sessions: PA-05 Tests of the Electroweak Gauge Theory / PL-06a Precision Tests of the Standard Model (Electroweak Gauge Theory (W, Z, Top, etc.)
Supporting papers: CERN-EP/99-130, Phys. Lett. B471 (1999) 293-307 =http://opal.web.cern.ch/Opal/pubs/paper/html/pr292.html
Notes:
Measurements of single W production in e+e- collisions have been performed using data collected with the OPAL detector at LEP, at centre-of-mass energies up to 202 GeV. Measurements of the triple gauge coupling parameters of the gWW vertex are obtained from the total event rate and from the kinematic distributions of the selected events.
Authors:The OPAL collaboration
Proposed speaker:
Contact person:David J Miller
(CERN),
dave.miller@cern.ch
Sessions: PA-05 Tests of the Electroweak Gauge Theory / PL-06a Precision Tests of the Standard Model (Electroweak Gauge Theory (W, Z, Top, etc.)
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 PN427 at http://opal.web.cern.ch/Opal/pubs/physnote/html/pn427.html
Notes:
Cross-sections and angular distributions for hadronic and lepton pair final states in e+e- collisions at centre-of-mass energy near 189 GeV, measured with the OPAL detector at LEP, are presented and compared with the predictions of the Standard Model. The results are used to measure the energy dependence of the electromagnetic coupling constant and to place 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. A search for the indirect effects of the gravitational interaction in extra dimensions on the mu-pair and tau-pair final states is also presented.
Authors:The OPAL collaboration
Proposed speaker:
Contact person:David J Miller
(CERN),
dave.miller@cern.ch
Sessions: PA-05 Tests of the Electroweak Gauge Theory / PL-06a Precision Tests of the Standard Model (Electroweak Gauge Theory (W, Z, Top, etc.)
Supporting papers: CERN-EP/99-097, accepted by Eur. Phys. J. C =http://opal.web.cern.ch/Opal/pubs/paper/html/pr286.html
Notes:
Cross-sections and angular distributions for hadronic and lepton pair final states in e+e- collisions at centre-of-mass energies between 192 GeV and 202 GeV, measured with the OPAL detector at LEP, are presented and compared with the predictions of the Standard Model. The results are used to measure the energy dependence of the electromagnetic coupling constant and to place limits on new physics as described by four-fermion contact interactions. 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.
Authors:The OPAL collaboration
Proposed speaker:
Contact person:David J Miller
(CERN),
dave.miller@cern.ch
Sessions: PA-05 Tests of the Electroweak Gauge Theory / PL-06a Precision Tests of the Standard Model (Electroweak Gauge Theory (W, Z, Top, etc.)
Supporting papers: OPAL Physics Note PN424 =http://opal.web.cern.ch/Opal/pubs/physnote/html/pn424.html
Notes:
The process e+e- -> gamma gamma (gamma) has been studied with the OPAL detector at centre-of-mass energies up at 189 GeV. This process is dominated by QED and any deviation of the measured differential cross-section from the well known prediction reveals physics beyond the standard model. These deviations can be parametrized in terms of contact interactions. But also an exited electron e* or a resonance X decaying to two photons can influence this process. Limits are set on cut-off parameters, the mass of e* and the cross-section for e+e- -> gamma X.
Authors:The OPAL collaboration
Proposed speaker:
Contact person:David J Miller
(CERN),
dave.miller@cern.ch
Sessions: PA-05 Tests of the Electroweak Gauge Theory / PL-06a Precision Tests of the Standard Model (Electroweak Gauge Theory (W, Z, Top, etc.)
Supporting papers: CERN-EP/99-088, Phys. Lett. B465 (1999) 303-314 =http://opal.web.cern.ch/Opal/pubs/paper/html/pr283.html
Notes:Also of interest to Parallel session 11, New Particle Search and Plenary session 7, New Particles and New Phenomena.
The cross-section ratio Rb = sigma(e+e- --> bbbar )/sigma(e+e- --> qqbar) and the bottom and charm forward-backward asymmetries AFBb and AFBc are measured using event samples collected by the OPAL detector at centre-of-mass energies between 130 and 189 GeV. Events with bottom quark production are selected with a secondary vertex tag, and a hemisphere charge algorithm is used to extract AFBb. In addition, the bottom and charm asymmetries are measured using leptons from semileptonic decays of heavy hadrons and pions from D* decays. The results are in agreement with the Standard Model predictions.
Authors:The OPAL collaboration
Proposed speaker:
Contact person:David J Miller
(CERN),
dave.miller@cern.ch
Sessions: PA-05 Tests of the Electroweak Gauge Theory / PL-06a Precision Tests of the Standard Model (Electroweak Gauge Theory (W, Z, Top, etc.)
Supporting papers: CERN-EP/99-170, submitted to Eur. Phys. J. C =http://opal.web.cern.ch/Opal/pubs/paper/html/pr297.html
Notes:Also of interest to parallel session 7, Heavy Flavour and Plenary session 3 Heavy Flavour Physics
A study of Z boson pair production in e+e- annihilation at center-of-mass energies near 183 GeV and 189 GeV is reported. Final states containing only leptons, (llll and llnunu) quark and lepton pairs (qqll and qqnunu) and only quarks (qqqq) have been studied. In all states with at least one Z boson decaying hadronically, qq and bb final states are considered separately using lifetime and event-shape tags, thereby improving the cross-section measurement. The Z-pair cross section is measured at energies between 183 and 189 GeV. Limits on anomalous ZZgamma and ZZZ couplings are derived.
Authors:The OPAL collaboration
Proposed speaker:
Contact person:David J Miller
(CERN),
dave.miller@cern.ch
Sessions: PA-05 Tests of the Electroweak Gauge Theory / PL-06a Precision Tests of the Standard Model (Electroweak Gauge Theory (W, Z, Top, etc.)
Supporting papers: CERN-EP-2000-017, Phys. Lett. B476 (2000) 256-272 =http://opal.web.cern.ch/Opal/pubs/paper/html/pr300.html
Notes:
A study of Z boson pair production in e+e- annihilation at center-of-mass energies above 190 GeV using the OPAL detector at LEP is reported. Final states containing only leptons, (llll and llnunu) quark and lepton pairs (qqll and qqnunu) and only quarks (qqqq) have been studied. In all states with at least one Z boson decaying hadronically, qq and bb final states are considered separately using lifetime and event-shape tags, thereby improving the cross-section measurement. The Z-pair cross section is measured at energies between 183 and 206 GeV. Limits on anomalous ZZgamma and ZZZ couplings are derived.
Authors:The OPAL collaboration
Proposed speaker:
Contact person:David J Miller
(CERN),
dave.miller@cern.ch
Sessions: PA-05 Tests of the Electroweak Gauge Theory / PL-06a Precision Tests of the Standard Model (Electroweak Gauge Theory (W, Z, Top, etc.)
Supporting papers: To be submitted to the conference and listed at http://opal.web.cern.ch/Opal/pubs/publications.html; Preliminary version available as OPAL Physics Note PN423 =http://opal.web.cern.ch/Opal/pubs/physnote/html/pn423.html
Notes:
The process e gamma -> eZ/gamma* is studied in e+e- collisions with the OPAL detector at LEP at a centre of mass energy of sqrt(s) = 189 GeV. The e+e- cross-section times the branching ratio of the Z/gamma* decaying into hadrons is measured within Lorentz invariant kinematic limits. The e gamma cross-section is measured as a function of the centre-of-mass energy of the e gamma. The distributions of the Mandelstam variables s, t, and u are measured as e+e- event rates and compared with the predictions from the Monte Carlo generators grc4f and PYTHIA. Further the differential e gamma cross-sections dsigma/dt and dsigma/du are measured.
Authors:The OPAL collaboration
Proposed speaker:
Contact person:David J Miller
(CERN),
dave.miller@cern.ch
Sessions: PA-05 Tests of the Electroweak Gauge Theory / PL-06a Precision Tests of the Standard Model (Electroweak Gauge Theory (W, Z, Top, etc.)
Supporting papers: OPAL Physics Note PN392 =http://opal.web.cern.ch/Opal/pubs/physnote/html/pn392.html
Notes:
Based on the analysis of data recorded during 2000 with the OPAL detector at LEP, several preliminary measurements and comparisons with the Standard Model expectations are described. In particular, results on cross-sections for hadronic, lepton pair, and multi-photon final states and on forward-backward asymmetries for the leptonic final states are presented. These results are used to determine the electromagnetic coupling constant at LEP2 energies and to put limits on new physics. Preliminary determinations of the cross-sections for WW and ZZ production are described. QCD studies of hadronic decays are also presented at these highest e+e- centre-of-mass energies.
Authors:The OPAL collaboration
Proposed speaker:
Contact person:David J Miller
(CERN),
dave.miller@cern.ch
Sessions: PA-05 Tests of the Electroweak Gauge Theory / PL-06a Precision Tests of the Standard Model (Electroweak Gauge Theory (W, Z, Top, etc.)
Supporting papers: To be submitted to the conference and listed on http://opal.web.cern.ch/Opal/pubs/publications.html
Notes:Also of interest to Parallel session 3, High Q^2: Jets + Perturbative QCD and Plenary session 11, High Q^2: Jets
The production rates of charmed hadrons in Z to ccbar decays are measured using the LEP I data collected with the ALEPH detector. The fractional decay width of the Z into cc pairs is determined from the sum of the production rates of various weakly decaying charmed states to be Rc=0.1738 +-0.0047+-0.0116.
Authors:ALEPH collaboration
Proposed speaker:
Contact person:Fabrizio Palla
(CERN),
Fabrizio.Palla@cern.ch
Sessions: PA-05 Tests of the Electroweak Gauge Theory / PL-06a Precision Tests of the Standard Model (Electroweak Gauge Theory (W, Z, Top, etc.)
Supporting papers: CERN EP 99-094
Notes:
The full data sample collected at and around the Z resonance by the ALEPH detector in the years 1991-1995 is analyzed to measure the forward-backward asymmetries in Z->bb and Z->cc decays. The analysis benefits from a recent reprocessing of the data, which has provided improved tracking capability and particle identification. The quark charge is tagged by means of identified electrons and muons produced in c and b semileptonic decays. An attempt has been made to optimise both the flavour and b->l/b->c->l process separation.
Authors:ALEPH collaboration
Proposed speaker:
Contact person:Fabrizio Palla
(CERN),
Fabrizio.Palla@cern.ch
Sessions: PA-05 Tests of the Electroweak Gauge Theory / PL-06a Precision Tests of the Standard Model (Electroweak Gauge Theory (W, Z, Top, etc.)
Supporting papers:
Notes:
Based on the analysis of about 200 pb^-1 of data recorded at centre-of-mass energies between 192-202 GeV with the OPAL detector at LEP, several preliminary measurements and comparisons with the Standard Model expectations are described. In particular, results on cross-sections for hadronic, lepton pair, and multi-photon final states and on forward-backward asymmetries for the leptonic final states are presented. These results are used to determine the electromagnetic coupling constant alpha_em at LEP2 energies and to put limits on new physics. Preliminary determinations of the cross-sections for WW and ZZ production are described. QCD studies of hadronic decays are also presented. All results are consistent with Standard Model expectations.
Authors:The OPAL collaboration
Proposed speaker:
Contact person:David J Miller
(CERN),
dave.miller@cern.ch
Sessions: PA-05 Tests of the Electroweak Gauge Theory / PL-06a Precision Tests of the Standard Model (Electroweak Gauge Theory (W, Z, Top, etc.)
Supporting papers: OPAL Physics Note PN420 =http://opal.web.cern.ch/Opal/pubs/physnote/html/pn420.html
Notes:Also of interest to Parallel session 3, High Q^2: Jets, perturbative QCD and Plenary session 11, High Q^2: Jets.
Very preliminary results on Standard Model processes in e+e- collisions at center-of-mass energies above 200 GeV will be presented, based on data taken with the ALEPH detector at LEP from April to July 2000. They could include analyses of two-fermion events, QCD studies of event shape variables and jet rates in hadronic events, as well as analyses of W and Z pair production. This note should be available from the ALEPH server for conference contributions, http://alephwww.cern.ch/ALPUB/oldconf/conferences.html, around July 21st.
Authors:ALEPH collaboration
Proposed speaker:
Contact person:Fabrizio Palla
(CERN),
Fabrizio.Palla@cern.ch
Sessions: PA-05 Tests of the Electroweak Gauge Theory / PL-06a Precision Tests of the Standard Model (Electroweak Gauge Theory (W, Z, Top, etc.)
Supporting papers:
Notes:
A search for Flavour Changing Neutral Currents is performed using data taken by the DELPHI detector at LEP 2. The data analysed were accumulated at centre-of-mass energies ranging from 192 to 202 GeV. A limit at 95% confidence level is obtained on the cross-section of the reaction e+e- --> tc + tu + CC.
Authors:DELPHI Collaboration
Proposed speaker:
Contact person:Clara Matteuzzi
(University of Milano),
Clara.Matteuzzi@cern.ch
Sessions: PA-05 Tests of the Electroweak Gauge Theory / PL-06a Precision Tests of the Standard Model (Electroweak Gauge Theory (W, Z, Top, etc.)
Supporting papers:
Notes:
The measurement of the luminosity at the OPAL interaction point is based on a Silicon-Tungsten Luminometer, which detects electrons from small-angle Bhabha scattering at angles between 25 and 58 mrad. The trajectories of incoming 45 GeV electrons or photons can be determined with a total systematic error of less than 7 microns. The total systematic measurement uncertainty on the luminosity is 3.4 10^-4, significantly below the theoretical error of 5.4 10^-4. Such precise measurement of the luminosity is crucial for determining the coupling of the Z-boson to invisible channels, such as neutrinos.
Authors:The OPAL collaboration
Proposed speaker:
Contact person:David J Miller
(CERN),
dave.miller@cern.ch
Sessions: PA-05 Tests of the Electroweak Gauge Theory / PL-06a Precision Tests of the Standard Model (Electroweak Gauge Theory (W, Z, Top, etc.)
Supporting papers: CERN-EP/99-136, submitted Eur. Phys. J. C =http://opal.web.cern.ch/Opal/pubs/paper/html/pr289.html
Notes:
We present an analysis of hadronic and leptonic cross sections and leptonic forward-backward asymmetries in electron-positron collisions with the OPAL detector at LEP I. During the 1993-1995 data-taking periods, a total of 2,879,138 hadronic and 332,691 leptonic decays have been recorded at three center-of-mass energies around the mass of the Z-boson. The results are combined with those previously published from data collected before 1993, making use of the full LEP I data sample of 161 pb^-1 of integrated luminosity and 4.5 10^6 selected Z-boson decays. These data are used to determine electroweak parameters and to perform stringent tests of the Standard Model.
Authors:The OPAL collaboration
Proposed speaker:
Contact person:David J Miller
(CERN),
dave.miller@cern.ch
Sessions: PA-05 Tests of the Electroweak Gauge Theory / PL-06a Precision Tests of the Standard Model (Electroweak Gauge Theory (W, Z, Top, etc.)
Supporting papers: To be submitted to the conference and listed on http://opal.web.cern.ch/Opal/pubs/publications.html
Notes:
New precision measurements of the tau lepton polarization and its forward-backward asymmetry at the Z resonance using the complete OPAL LEPI dataset are described. The measurements are based on a simultaneous analysis of the tau->rho nu, tau->pi nu, tau-> e nu nu, tau-> mu nu nu, and tau-> a_1 nu decays from a sample of 150k e+e- -> tau+ tau- candidates corresponding to an integrated luminosity of 163/pb. A maximum likelihood fit to kinematic decay observables and the polar angle of the tau- when in the range -0.9<cos theta<0.9 yields the tau and electron neutral current asymmetries. These measurements provide a precision test of the hypothesis of neutral current lepton universality and an accurate determination of sin^2 theta_W within the context of the Standard Model.
Authors:The OPAL collaboration
Proposed speaker:
Contact person:David J Miller
(CERN),
dave.miller@cern.ch
Sessions: PA-05 Tests of the Electroweak Gauge Theory / PL-06a Precision Tests of the Standard Model (Electroweak Gauge Theory (W, Z, Top, etc.)
Supporting papers: To be submitted to the conference and listed on http://opal.web.cern.ch/Opal/pubs/publications.html
Notes:Also of interest in Parallel session 7, Heavy Flavours and Plenary session 3, Heavy Flavour Physics
A measurement of triple gauge boson couplings is presented, based on W-pair data recorded by the OPAL detector at LEP during 1999 at cenntre-of-mass energies of 192-202 GeV with an integrated luminosity of 220 inverse picobarns. These results are combined with our previous measurements at centre-of-mass energies of 161-189 GeV and with results from the single W and single photon processes.
Authors:The OPAL collaboration
Proposed speaker:
Contact person:David J Miller
(CERN),
dave.miller@cern.ch
Sessions: PA-05 Tests of the Electroweak Gauge Theory / PL-06a Precision Tests of the Standard Model (Electroweak Gauge Theory (W, Z, Top, etc.)
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 PN425 at http://opal.web.cern.ch/Opal/pubs/physnote/html/pn425.html
Notes:
A measurement of the polarisation of W bosons in semi-leptonically decaying W-pairs produced at 189 GeV is presented. It was found that (19.9 +/- 4.1 +/- 1.5)% of the total W bosons were longitudinally polarised. (80.1 +/- 5.8 +/- 1.5)% of the W-pairs contained two transversely polarised bosons, (18.8+/- 8.6 +/- 1.8)% contained two longitudinally polarised bosons and the remaining (2.2 +/- 11.9 +/- 3.7)% W-pairs contained one boson of each polarisation. The spin properties of the leptonically decaying W boson in the W-pairs was used to measure the CP-violating trilinear gauge boson couplings. We obtained the following, tilde-kappa-z = -0.20(+0.10 -0.07), tilde-lambda-z = -0.18(+0.24 -0.16) and gz4 = -0.02(+0.32 -0.32) These results are consistent with Standard Model expectations.
Authors:The OPAL collaboration
Proposed speaker:
Contact person:David J Miller
(CERN),
dave.miller@cern.ch
Sessions: PA-05 Tests of the Electroweak Gauge Theory / PL-06a Precision Tests of the Standard Model (Electroweak Gauge Theory (W, Z, Top, etc.)
Supporting papers: To be submitted to the conference and listed on http://opal.web.cern.ch/Opal/pubs/publications.html
Notes:
The triple gauge boson couplings between two W bosons and a photon have been studied using photonic events with missing energy. The data sample was obtained at LEP with the OPAL detector. The centre of mass energy = 189 GeV with a total luminosity of 187.2 pb^-1. Constraints on the gauge coupling parameters Delta kappa_gamma and lambda_gamma have been determined by fitting the differential cross section in bins of energy and cos(theta).
Authors:The OPAL collaboration
Proposed speaker:
Contact person:David J Miller
(CERN),
dave.miller@cern.ch
Sessions: PA-05 Tests of the Electroweak Gauge Theory / PL-06a Precision Tests of the Standard Model (Electroweak Gauge Theory (W, Z, Top, etc.)
Supporting papers: To be submitted to the conference and listed on http://opal.web.cern.ch/Opal/pubs/publications.html
Notes:
Using approximately 240 pb-1 of data collected at centre-of-mass energies around 183 GeV and 189 GeV with the OPAL detector at LEP, a sample of W-pair events is selected. A value of the partial decay width for W->cX is extracted from jet properties, lifetime information, and semi-leptonic decay products of the charm quark. This measurement allows a direct test of unitarity of the CKM matrix in three generations within the framework of the Standard Model. Furthermore, the measured value can also be used to determine the value of Vcs using the measured values of the other CKM matrix elements.
Authors:The OPAL collaboration
Proposed speaker:
Contact person:David J Miller
(CERN),
dave.miller@cern.ch
Sessions: PA-05 Tests of the Electroweak Gauge Theory / PL-06a Precision Tests of the Standard Model (Electroweak Gauge Theory (W, Z, Top, etc.)
Supporting papers: To be submitted to the conference and listed on http://opal.web.cern.ch/Opal/pubs/publications.html
Notes:Also of interest to parallel session 7, Heavy Flavour physics and Plenary session 3, Heavy Flavour physics
The process e+e- -> gamma gamma (gamma) has been studied with the OPAL detector at centre-of-mass energies up to 202 GeV. This process is dominated by QED and any deviation of the measured differential cross-section from the well known prediction reveals physics beyond the standard model. These deviations can be parametrized in terms of contact interactions. But also an exited electron e* or a resonance X decaying to two photons can influence this process. Limits are set on cut-off parameters, the mass of e* and the cross-section for e+e- -> gamma X.
Authors:The OPAL collaboration
Proposed speaker:
Contact person:David J Miller
(CERN),
dave.miller@cern.ch
Sessions: PA-05 Tests of the Electroweak Gauge Theory / PL-06a Precision Tests of the Standard Model (Electroweak Gauge Theory (W, Z, Top, etc.)
Supporting papers: To be submitted to the conference and listed on http://opal.web.cern.ch/Opal/pubs/publications.html
Notes:Also of interest to parallel session 11, Search for New Particles and Phenomena and Plenary session 7a, Search for New Particles and Phenomena
A search for anomalous Z-Z-gamma and Z-gamma-gamma couplings in the process e+e- -> Z gamma has been performed using data collected with the OPAL detector at LEP2 energies. The study is based on the analysis of the total rate and the properties of the (qbar q gamma) and (nubar nu gamma) final states. Consistency with the Standard Model expectations has been observed, indicating no evidence for anomalous couplings, and 95% CL upper limits have been derived.
Authors:The OPAL collaboration
Proposed speaker:
Contact person:David J Miller
(CERN),
dave.miller@cern.ch
Sessions: PA-05 Tests of the Electroweak Gauge Theory / PL-06a Precision Tests of the Standard Model (Electroweak Gauge Theory (W, Z, Top, etc.)
Supporting papers: To be submitted to the conference and listed on http://opal.web.cern.ch/Opal/pubs/publications.html
Notes:Also of interest to parallel session 11, Search for New Particles and Phenomena and Plenary session 7a, Search for New Particles and Phenomena
The cross-section ratios Ru, Rd and Rs are measured for individual light quarks using event samples collected with the OPAL detector at LEP at centre-of-mass energies between 189 and 202 GeV. The analysis uses high momentum charged pions, charged and neutral kaons, protons and Lambda baryons to idenitify the different light flavour quarks events on a statistical basis. The probabilities for the different particle types to originate from particular primary quarks are determined directly from data taken at the Z0 peak, thus making possible a hadronisation model-independent measurement.
Authors:The OPAL collaboration
Proposed speaker:
Contact person:David J Miller
(CERN),
dave.miller@cern.ch
Sessions: PA-05 Tests of the Electroweak Gauge Theory / PL-06a Precision Tests of the Standard Model (Electroweak Gauge Theory (W, Z, Top, etc.)
Supporting papers: To be submitted to the conference and listed on http://opal.web.cern.ch/Opal/pubs/publications.html
Notes:
Final states from neutral current four fermion events are analysed. Total and differential event rates are compared with the Monte Carlo predictions. The data correspond to a total of about 440 pb^-1 recorded with the OPAL detector in the years 1997 to 1999 at center-of-mass energies between 189 and 202 GeV.
Authors:The OPAL collaboration
Proposed speaker:
Contact person:David J Miller
(CERN),
dave.miller@cern.ch
Sessions: PA-05 Tests of the Electroweak Gauge Theory / PL-06a Precision Tests of the Standard Model (Electroweak Gauge Theory (W, Z, Top, etc.)
Supporting papers: To be submitted to the conference and listed on http://opal.web.cern.ch/Opal/pubs/publications.html
Notes:
Data on muon pair production obtained by the OPAL collaboration at and around the Z peak are analysed. Small angular mismatches between the directions of the two muons are used to estimate the effects of initial state photon radiation and initial-final state radiation interference on the forward-backward asymmetry of muon pair production and its dependence on the invariant mass of the pair.
Authors:The OPAL collaboration
Proposed speaker:
Contact person:David J Miller
(CERN),
dave.miller@cern.ch
Sessions: PA-05 Tests of the Electroweak Gauge Theory / PL-06a Precision Tests of the Standard Model (Electroweak Gauge Theory (W, Z, Top, etc.)
Supporting papers: To be submitted to the conference and listed on http://opal.web.cern.ch/Opal/pubs/publications.html
Notes:
The properties of the Z resonance are measured from the analysis of 4.5 million Z decays into fermion pairs collected with the ALEPH detector at LEP. The resonance parameters are measured to be M_Z=(91.1885 +- 0.0031) Gev/c^2, Gamma_Z= (2.4951 +- 0.0043) GeV, sigma=(41.559 +- 0.058)nb and, combining the three lepton flavours, R_l= 20.725+- 0.039. The number of light neutrino species is N_nu=2.983+-0.013 and the strong coupling constant is alpha_s(MZ) = 0.114+-0.004+-0.002(QCD) +0.005 log_10(MH/(150 GeV/c^2)). The lepton pair forward-backward asymmetry is measured to be 0.0173+-0.0016 from which the effective weak mixing angle is 0.23089+-0.00089.
Authors:ALEPH collaboration
Proposed speaker:
Contact person:Fabrizio Palla
(CERN),
Fabrizio.Palla@cern.ch
Sessions: PA-05 Tests of the Electroweak Gauge Theory / PL-06a Precision Tests of the Standard Model (Electroweak Gauge Theory (W, Z, Top, etc.)
Supporting papers: CERN-EP 99-104
Notes:
A search for Colour Reconnection effects between the decay products of the W's has been performed with data taken at centre-of-mass energies from 183 GeV up to 202 GeV. The particle and energy flow distributions between jets, and several Lorentz-invariant distributions have been studied and compared with different Colour Reconnection models.
Authors:ALEPH collaboration
Proposed speaker:
Contact person:Fabrizio Palla
(CERN),
Fabrizio.Palla@cern.ch
Sessions: PA-05 Tests of the Electroweak Gauge Theory / PL-06a Precision Tests of the Standard Model (Electroweak Gauge Theory (W, Z, Top, etc.)
Supporting papers:
Notes:
Bose-Einstein correlations are studied in semileptonic WW --> qqbarlnu and fully hadronic WW --> qqbarqqbar W-pair decays at centre-of-mass energies of 192, 196, 200 and 202 GeV. A Monte Carlo model of Bose-Einstein correlations based on the JETSET hadronization scheme was tuned to the Z data and reproduces the correlations in the WW --> qqbarlnu events. The same Monte Carlo reproduces the correlations in the WW --> qqbarqqbar channel assuming independent fragmentation of the two W's. A variant of this model with Bose-Einstein correlations between decay products of different W's is disfavoured.
Authors:ALEPH collaboration
Proposed speaker:
Contact person:Fabrizio Palla
(CERN),
Fabrizio.Palla@cern.ch
Sessions: PA-05 Tests of the Electroweak Gauge Theory / PL-06a Precision Tests of the Standard Model (Electroweak Gauge Theory (W, Z, Top, etc.)
Supporting papers:
Notes:
Bose-Einstein correlations are studied in semileptonic WW --> qqbarlnu and fully hadronic WW --> qqbarqqbar W-pair decays at centre-of-mass energies of 172, 183 and 189 GeV. A Monte Carlo model of Bose-Einstein correlations based on the JETSET hadronization scheme was tuned to the Z data and reproduces the correlations in the WW --> qqbarlnu events. The same Monte Carlo reproduces the correlations in the WW --> qqbarqqbar channel assuming independent fragmentation of the two W's. A variant of this model with Bose-Einstein correlations between decay products of different W's is disfavoured.
Authors:ALEPH collaboration
Proposed speaker:
Contact person:Fabrizio Palla
(CERN),
Fabrizio.Palla@cern.ch
Sessions: PA-05 Tests of the Electroweak Gauge Theory / PL-06a Precision Tests of the Standard Model (Electroweak Gauge Theory (W, Z, Top, etc.)
Supporting papers: CERN-EP 99-173
Notes:
The mass and the width of the W boson is determined by the direct reconstruction of W decays in WW->qqqq and WW->lvqq events, supplemented by measurements using the kinematic properties of the leptons in the WW->lvlv decay channel. The main sample of W pairs is selected from an integrated luminosity of 174 pb-1 collected in 1998 at a centre-of-mass energy of 188.63 GeV. The combination of the mass measurement presented in this paper together with those derived previously from data samples collected at all lower centre-of-mass energies gives mW = 80.418+-0.061(stat.)+-0.038(syst.)+-0.019(FSI)+-0.017(LEP) GeV/c^2 Gamma_W = 2.24 +- 0.20(stat.) +- 0.13(syst.)GeV/c^2.
Authors:ALEPH collaboration
Proposed speaker:
Contact person:Fabrizio Palla
(CERN),
Fabrizio.Palla@cern.ch
Sessions: PA-05 Tests of the Electroweak Gauge Theory / PL-06a Precision Tests of the Standard Model (Electroweak Gauge Theory (W, Z, Top, etc.)
Supporting papers: CERN-EP 2000-045
Notes:
Preliminary constraints on QG WWgg couplings have been set from acoplanar photon pair events at 189-202 GeV.The present analysis (performed in a limited kinematical range) uses the cross-section variation due to the QGC hypothesis.
Authors:ALEPH collaboration
Proposed speaker:
Contact person:Fabrizio Palla
(CERN),
Fabrizio.Palla@cern.ch
Sessions: PA-05 Tests of the Electroweak Gauge Theory / PL-06a Precision Tests of the Standard Model (Electroweak Gauge Theory (W, Z, Top, etc.)
Supporting papers:
Notes:
The e+e- -> ZZ cross section at sqrt(s)=191.6, 195.5, 199.5, and 201.6 GeV has been measured using the ALEPH detector and the 1999 LEP2 data sample which represents integrated luminosities of 29.0, 80.1, 84.9, and 37.3 pb-1, respectively. The selections cover all of the visible ZZ final states and yield cross section measurements of sigma_NC2(191.6 GeV) = 0.53 +{0.34} -{0.27} pb, sigma_NC2(195.5 GeV) = 0.69 +{0.23} -{0.20} pb, sigma_NC2(199.5 GeV) = 0.70 +{0.22} -{0.20} pb, and sigma_NC2(201.6 GeV) = 0.70 +{0.33} -{0.23} pb.
Authors:ALEPH collaboration
Proposed speaker:
Contact person:Fabrizio Palla
(CERN),
Fabrizio.Palla@cern.ch
Sessions: PA-05 Tests of the Electroweak Gauge Theory / PL-06a Precision Tests of the Standard Model (Electroweak Gauge Theory (W, Z, Top, etc.)
Supporting papers:
Notes:
The production of WW pairs is analysed in a data sample collected by ALEPH between 192 and 202 GeV centre-of-mass energies, corresponding to an integrated luminosity of 236.96 pb-1. The total W-pair cross section is measured at each LEP centre-of-mass energy and agree with the most up-to-date Standard Model calculations. The decay branching fraction of the W boson into hadrons is measured to be B(W -> hadrons) = 67.09 +- 0.46 (stat.) +- 0.32 (syst.) %, allowing a determination of the CKM matrix element Vcs = 0.956 +- 0.021 (stat.) +- 0.015 (syst.).
Authors:ALEPH collaboration
Proposed speaker:
Contact person:Fabrizio Palla
(CERN),
Fabrizio.Palla@cern.ch
Sessions: PA-05 Tests of the Electroweak Gauge Theory / PL-06a Precision Tests of the Standard Model (Electroweak Gauge Theory (W, Z, Top, etc.)
Supporting papers:
Notes:
The ee -> ZZ cross section at sqrt(s)=182.7 and 188.6 GeV has been measured using the ALEPH detector. The analysis covers all of the visible ZZ final states and yields cross section measurements of sigma_ZZ(182.7 GeV) = 0.11 +- (0.16,0.11) (stat.) +- 0.04 (syst.) pb and sigma_ZZ(188.6 GeV) = 0.67 +- 0.13 (stat.) +- 0.04 (syst.) pb consistent with the Standard Model expectations.
Authors:ALEPH collaboration
Proposed speaker:
Contact person:Fabrizio Palla
(CERN),
Fabrizio.Palla@cern.ch
Sessions: PA-05 Tests of the Electroweak Gauge Theory / PL-06a Precision Tests of the Standard Model (Electroweak Gauge Theory (W, Z, Top, etc.)
Supporting papers: CERN-EP 99-141
Notes:
The production of W-pairs is analysed in a data sample collected by ALEPH at a mean centre-of-mass energy of 188.6 GeV, corresponding to an integrated luminosity of 174.2 pb-1. Assuming Standard Model branching fractions, the total W-pair cross section is measured to be 15.71 +- 0.34 (stat) +- 0.18 (syst) pb. The decay branching fraction of the W boson into hadrons is measured to be BR (W -> hadrons) = 66.97 +- 0.65 (stat) +- 0.32 (syst) %, allowing a determination of the CKM matrix element |V(cs)|= 0.951 +- 0.030 (stat) +- 0.015 (syst).
Authors:ALEPH collaboration
Proposed speaker:
Contact person:Fabrizio Palla
(CERN),
Fabrizio.Palla@cern.ch
Sessions: PA-05 Tests of the Electroweak Gauge Theory / PL-06a Precision Tests of the Standard Model (Electroweak Gauge Theory (W, Z, Top, etc.)
Supporting papers: CERN-EP 2000-052
Notes:
We present an investigation possible colour reconnection signatures in selected regions of the phase space for particles in multihadronic WW decays. The data were collected with the ALEPH detector at LEP at energies above the WW threshold. The data are compared with various Monte Carlo models, which have been tuned to predict consistently the same charged track multiplicities for semileptonic W-pair events.
Authors:ALEPH collaboration
Proposed speaker:
Contact person:Fabrizio Palla
(CERN),
Fabrizio.Palla@cern.ch
Sessions: PA-05 Tests of the Electroweak Gauge Theory / PL-06a Precision Tests of the Standard Model (Electroweak Gauge Theory (W, Z, Top, etc.)
Supporting papers:
Notes:
We present an investigation possible colour reconnection signatures in selected regions of the phase space for particles in multihadronic WW decays. The data were collected with the ALEPH detector at LEP at energies above the WW threshold. The data are compared with various Monte Carlo models, which have been tuned to predict consistently the same charged track multiplicities for semileptonic W-pair events.
Authors:ALEPH collaboration
Proposed speaker:
Contact person:Fabrizio Palla
(CERN),
Fabrizio.Palla@cern.ch
Sessions: PA-05 Tests of the Electroweak Gauge Theory / PL-06a Precision Tests of the Standard Model (Electroweak Gauge Theory (W, Z, Top, etc.)
Supporting papers:
Notes:
The mass of the W boson is determined by the direct reconstruction of W decays in WW -> qqbar qqbar and WW -> ln qqbar events. The sample of W pairs is selected from an integrated luminosity of 237 pb^{-1} with centre-of-mass energies ranging from 192 to 202 GeV. The combination of these measurements with those from W-pair data samples collected at all lower centre-of-mass energies gives m_W = 80.440 +- 0.044(stat.) +- 0.040(syst.) +- 0.020(FSI) +- 0.017(LEP) GeV G_W = 2.17 +- 0.16(stat.) +- 0.12(syst.) GeV.
Authors:ALEPH collaboration
Proposed speaker:
Contact person:Fabrizio Palla
(CERN),
Fabrizio.Palla@cern.ch
Sessions: PA-05 Tests of the Electroweak Gauge Theory / PL-06a Precision Tests of the Standard Model (Electroweak Gauge Theory (W, Z, Top, etc.)
Supporting papers:
Notes:
The triple gauge-boson couplings of the W boson are studied based on the data collected with the ALEPH detector at energies above 200 GeV. The triple gauge-boson couplings, Dg_z, Dk_g and Lambda_g, have been measured using W-pair events, single-W production and single-gamma production. In addition W-pair events are used to set limits on the C- or P-violating couplings g^V_4, g^V_5, K_V, and Lambda_V, where V denotes either gamma or Z.
Authors:ALEPH collaboration
Proposed speaker:
Contact person:Fabrizio Palla
(CERN),
Fabrizio.Palla@cern.ch
Sessions: PA-05 Tests of the Electroweak Gauge Theory / PL-06a Precision Tests of the Standard Model (Electroweak Gauge Theory (W, Z, Top, etc.)
Supporting papers:
Notes:
The four fermion process e^+e^- -> e nu f fbar', compatible with single W production, has been studied using the data recorded with the ALEPH detector at centre-of-mass energies between 161 and 202 GeV, corresponding to an integrated luminosity of 490 pb^{-1}. The cross sections for single W production have been measured and are in good agreement with the Standard Model expectations. The average ratio between the measured single W cross sections and the standard model expectations is found to be 0.87 +- 0.13 (stat.) +- 0.09 (syst.) +- 0.05 (theory).
Authors:ALEPH collaboration
Proposed speaker:
Contact person:Fabrizio Palla
(CERN),
Fabrizio.Palla@cern.ch
Sessions: PA-05 Tests of the Electroweak Gauge Theory / PL-06a Precision Tests of the Standard Model (Electroweak Gauge Theory (W, Z, Top, etc.)
Supporting papers:
Notes:
Four fermion processes with a particle lost in the beam pipe and four fermions plus a visible photon final-states are studied at LEP, to perform precision tests of the electroweak theory. Both are of interest for the investigation of non-abelian gauge couplings (TGC,QGC). To obtain adequate theoretical predictions, exact matrix elements, including fermion masses, are computed and higher-order QED corrections to such processes are analyzed, paying particular attention to the process of single-W production. Numerical predictions are shown in realistic situations for LEP experiments and compared with existing results. The up-to-date theoretical situation, as documented by the activity of the four fermion working group of the LEP2 Monte Carlo Workshop (CERN), is also reviewed.
Authors:G. Montagna, M. Moretti, O. Nicrosini, M. Osmo, A. Pallavicini, F. Piccinini
Proposed speaker: Fulvio Piccinini
Contact person:Fulvio Piccinini
(Universita` di Pavia and INFN, Sezione di Pavia),
Fulvio.Piccinini@pv.infn.it
Sessions: PA-05 Tests of the Electroweak Gauge Theory / PL-06a Precision Tests of the Standard Model (Electroweak Gauge Theory (W, Z, Top, etc.)
Supporting papers: Draft of the four fermion working group of the LEP2 Monte Carlo Workshop held at CERN (to appear soon) and references therein
Notes:
Radiative corrections to impact factors of a photon and an electron to lowest order are obtained.We show validity of the generalized eikonal representation for small-angle scattering amplitudes. Application to azimuthal asymmetry in DVCS is considered.
Authors:M.Galynsky, L.Lipatov, T.Shishkina, E.A.Kuraev
Proposed speaker: E.A.Kuraev
Contact person:Eduard E. Kuraev
(Joint Institute for nuclear research),
kuraev@thsun1.jinr.ru
Sessions: PA-05 Tests of the Electroweak Gauge Theory /
Supporting papers:
Notes:
The triple gauge-boson couplings are studied based on the data collected at centre-of-mass energies of 182.66 GeV and 188.63 GeV , corresponding to integrated luminosities of 56.81 pb-1 and 174.20 pb-1 , respectively. The triple gauge-boson couplings, Dgz, Dkg and Lambda_g, have been measured using W-pair events at 183 and 189 GeV, single-W production at 189 GeV and single-gamma production at 189 GeV. In addition W-pair events are used to set limits on the C- or P-violating couplings g^V_4, g^V_5, K_V, and Lambda_V, where V denotes either gamma or Z. No deviations from the Standard Model expectations are observed.
Authors:ALEPH collaboration
Proposed speaker:
Contact person:Fabrizio Palla
(CERN),
Fabrizio.Palla@cern.ch
Sessions: PA-05 Tests of the Electroweak Gauge Theory / PL-06a Precision Tests of the Standard Model (Electroweak Gauge Theory (W, Z, Top, etc.)
Supporting papers:
Notes:
Eigenvalues of the Breit Equation with the static Coulomb potential have been found for the singlet and the triplet cases with numericaly computer calculation.
Authors:H. Kasari and Y. Yamaguchi
Proposed speaker: H. Kasari
Contact person:Hikoya Kasari
(Tokai Univ.),
kasari@keyaki.cc.u-tokai.ac.jp
Sessions: PA-05 Tests of the Electroweak Gauge Theory / PL-06a Precision Tests of the Standard Model (Electroweak Gauge Theory (W, Z, Top, etc.)
Supporting papers: Y. Yamaguchi "Eigenvalues of the Breit Equation" Progress of theoretical Physics to be published.
Notes:There are no apporopriate session but well PA-05 and PL-06 are related (see 2).
Sudakov double logarithms originating from massive boson exchange can lead to significant corrections to the cross sections of the observable processes at future linear $e^+e^-$ collider experiments in the TeV range. The most powerful method to obtain double logarithmic asymptotics of scattering amplitudes is the infrared evolution equation. This method is applied in the case of broken gauge symmetry, in particular in the Standard Model of electroweak processes, for description of both non-radiative processes and processes accompanied by soft gauge boson emission. In all cases the Sudakov double logarithms are found to exponentiate, although the Poisson distribution for photon emissions is violated.
Authors:V.S. Fadin, L.N. Lipatov, A.D. Martin, M. Melles
Proposed speaker: V.S. Fadin
Contact person:Victor Sergeevich Fadin
(Institute for Nuclear Physics),
fadin@inp.nsk.su
Sessions: PA-05 Tests of the Electroweak Gauge Theory /
Supporting papers:
Notes:
The study of single top-quark production processes is a very important part of research programs at TeV energy colliders. We present a review of basic results on single top-quark physics and compare the potential of different colliders. Single top provides an additional to the top pair mechanism of the top-quark production. In contrast to the top pair production the rate of single top production is directly proportional to the Wtb coupling. This allows investigation if the coupling structure with the highest possible accuracy and measurement of the top quark width. The single top processes have interesting spin properties. The processes are sensitive to various anomalous couplings. The rate of single top is typically smaller than the top pair rate but it is large enough to be an important background to Higgs production and to various "new physics" processes. For example, at the upgraded Tevatron and the LHC the single top rates in the Standard Model are about 3.5 pb and 320 pb respectively.
Authors:E. Boos
Proposed speaker: E. Boos
Contact person:Edward E. Boos
(Institute of Nuclear Physics of Moscow State Univ.),
boos@theory.npi.msu.su
Sessions: PA-05 Tests of the Electroweak Gauge Theory /
Supporting papers: E.Boos et al, Top Quark Production in the Reaction $e^+e^- \rightarrow e \nu t b $ at Linear Collider Energies. Z.Phys. C70 (1996) 255-261. E.Boos, A.Pukhov, M.Sachwitz, H.J.Schreiber, Probing Anomalous Wtb Coupling via Single Top Production at TeV Energy $\gamma e $ Colliders. Phys.Lett. B 404 (1997) 119-123. A.P. Heinson, A.S. Belyaev, E.E.Boos, Single Top Quarks at the Fermilab Tevatron Phys.Rev.D56 (1997) 3114-3128. A.S. Belyaev, E.E.Boos, L.V. Dudko, Single Top Quark at Future Hadron Colliders: Complete Signal and Background Study. Phys.Rev.D59:075001,1999 E.Boos, L.Dudko, Th.Ohl, Complete Calculations of $Wbbar{b}$ and $Wbbar{b}+jet$ Production at Tevatron and LHC: Probing Anomalous $Wtb$ Coupling in Single Top Production. Eur.Phys.J. C11 (1999) 473 A.Belyaev, E.Boos Single Top Quark tW + X Production at the LHC: a Closer Look. Preprint CERN-TH-2000-093, Mar 2000, 9pp. hep-ph/0003260
Notes:
We summarize preliminary results obtained from data collected during the year 2000 at increased centre-of-mass energies. The data discussed here comprise measurements of total cross sections and forward-backward asymmetries for fermion-pair production e+e- --> f bar(f) gamma, studies of hadronic event shape variables, measurements of the strong coupling constant and studies of photonic final states. In addition, a measurement of the W pair cross section and an update on the determination of W boson properties are presented.
Authors:L3 Collaboration
Proposed speaker: L3 speaker
Contact person:Simonetta Gentile
(CERN),
Simonetta.Gentile@cern.ch
Sessions: PA-05 Tests of the Electroweak Gauge Theory / PL-06a Precision Tests of the Standard Model (Electroweak Gauge Theory (W, Z, Top, etc.)
Supporting papers:
Notes:in preparation
With an upgraded Beijing Spectrometer (BESII) at the Beijing Electron Positron Collider (BEPC), the BES collaboration finished an R scan in the energy region from 2 to 5 GeV. Preliminary R values for all 85 scanned energy points will be presented. This measurement will make an important contribution to the precision determination of $\alpha{M_Z^2}$, the QED coupling constant evaluated at the Z pole. The present uncertainty is a serious limit to further progress in the determination of the Higgs mass from radiative corrections in the Standard Model. The results can also contribute to the interpretation of muon g-2 measurement.
Authors:The BES collaboration
Proposed speaker: Zhengguo Zhao
Contact person:Zhengguo Zhao
(Institiute of High Energy Physics),
zhaozg@pony1.ihep.ac.cn
Sessions: PA-05 Tests of the Electroweak Gauge Theory / PL-06b Precision Tests of the Standard Model (New Results from g-2 Experiment)
Supporting papers:
Notes:the talk can be arranged as a plenary one together with g-2 experiment
An improved measurement of the forward-backward asymmetry in Z->b b-bar decays is presented, which makes use of the full LEP 1 statistics. Data are analysed in bins of the polar angle of the event axis, using a jet charge technique. Improved b-tagging performance and b-jet charge determination are achieved by using a neural network combinations. The mean b-jet hemisphere charge is measured directly from the data. From the value of the forward-backward asymmetry, a measurement of the electroweak mixing angle is derived.
Authors:ALEPH collaboration
Proposed speaker:
Contact person:Fabrizio Palla
(CERN),
Fabrizio.Palla@cern.ch
Sessions: PA-05 Tests of the Electroweak Gauge Theory / PL-06a Precision Tests of the Standard Model (Electroweak Gauge Theory (W, Z, Top, etc.)
Supporting papers:
Notes:
Using the 160 pb-1 of data accumulated at LEP 1 by ALEPH, the polarisation of the taus has been measured. This work uses new data, the sample collected from 1993 to 1995, and a reanalysis of the published data, the 1990 to 1992 sample. The study of the polarisation as a function of the polar angle yelds the two parameters, A_e=0.1505+-0.0069 and A_tau=0.1452+-0.0061, consistent with the hypothesis of electron-tau universality. Assuming universality one obtains A_e-tau=0.1475+-0.0046 from which the effective weak mixing angle is derived: sin^2(theta_eff)=0.23145+-0.00058.
Authors:ALEPH collaboration
Proposed speaker:
Contact person:Fabrizio Palla
(CERN),
Fabrizio.Palla@cern.ch
Sessions: PA-05 Tests of the Electroweak Gauge Theory / PL-06a Precision Tests of the Standard Model (Electroweak Gauge Theory (W, Z, Top, etc.)
Supporting papers:
Notes:
Trilinear neutral gauge boson couplings of the type Zgg and ZZg have been studied with the DELPHI detector at center of mass energies=189, 192, 196, 200 and 202 GeV. Limits are derived on these couplings from an analysis of the reactions e+e- --->g + invisible particles and e+e- --->g+ q-qbar for real photons. In the case of off-mass shell photons, the channels e+e- --->monojet e+e- --->mu-mubar have been studied.
Authors:DELPHI Collaboration
Proposed speaker:
Contact person:Clara Matteuzzi
(),
Clara.Matteuzzi@cern.ch
Sessions: PA-05 Tests of the Electroweak Gauge Theory / PL-06a Precision Tests of the Standard Model (Electroweak Gauge Theory (W, Z, Top, etc.)
Supporting papers:
Notes:Paper will be sent later
Measurements of the trilinear gauge boson couplings WWgamma and WWZ are presented from data taken by DELPHI up to 1999 at energies ranging from 183 GeV to 202 GeV. Values are determined for Delta g_1^z and Delta kappa_gamma, the differences of the WWZ charge coupling and of the WWgamma dipole coupling from their Standard Model values, and for lambda_gamma, the WWgamma quadrupole coupling. A measurement of the magnetic dipole and electric quadrupole moment of the W is extracted from the results for Delta kappa_gamma and lambda_gamma. The study uses data from the final states jjlnu, jjjj, lX, jjX and gammaX, where j represents a quark jet, l an identified lepton and X missing four-momentum. Current data have also been used to put stringent constraints to a possible anomalous enhancement of Re(epsilon'/epsilon).The results from energies up to 189 GeV will shortly be sent for publication.
Authors:DELPHI Collaboration
Proposed speaker:
Contact person:Clara Matteuzzi
(),
Clara.Matteuzzi@cern.ch
Sessions: PA-05 Tests of the Electroweak Gauge Theory / PL-06a Precision Tests of the Standard Model (Electroweak Gauge Theory (W, Z, Top, etc.)
Supporting papers:
Notes:Paper will be sent later
The cross-section for the process e+e-->W+W- was measured with the data sample collected by DELPHI at centre-of-mass energies of approximately 192, 196, 200 and 202 GeV and corresponding to a total integrated luminosity of 224 pb-1. The branching ratios of the W decay were also measured; from them the value of |Vcs| was extracted. The results are compared with the most recent calculations in the framework of the Standard Model.
Authors:DELPHI Collaboration
Proposed speaker:
Contact person:Clara Matteuzzi
(),
Clara.Matteuzzi@cern.ch
Sessions: PA-05 Tests of the Electroweak Gauge Theory / PL-06a Precision Tests of the Standard Model (Electroweak Gauge Theory (W, Z, Top, etc.)
Supporting papers:
Notes:Paper will be sent later
We report on measurements of the four-fermion final states originating from neutral current processes, in the data sample collected by the DELPHI detector at centre-of-mass energies ranging from 183 to 202 GeV. The measurements cover a wide range of the possible final four-fermion configurations: purely leptonic (llll), hadronic and leptonic (eeqq, mumuqq), monojet (nunuqq), and hadronic final states (qqqq with low mass qq pair). The preliminary measurements of the differential cross sections for the production of the various final states have been compared with the Standard Model expectations. The Zgamma* contribution to mumu qq, eeqq, nunu qq, and qqqq final states was estimated.
Authors:DELPHI Collaboration
Proposed speaker:
Contact person:Clara Matteuzzi
(),
Clara.Matteuzzi@cern.ch
Sessions: PA-05 Tests of the Electroweak Gauge Theory / PL-06a Precision Tests of the Standard Model (Electroweak Gauge Theory (W, Z, Top, etc.)
Supporting papers:
Notes:Paper will be sent later
Measurements on processes of final states WW, ZZ, single W and Z as well as other 4-fermion interactions from data taken at LEP in the year 2000 will be presented.
Authors:DELPHI Collaboration
Proposed speaker:
Contact person:Clara Matteuzzi
(),
Clara.Matteuzzi@cern.ch
Sessions: PA-05 Tests of the Electroweak Gauge Theory / PL-06a Precision Tests of the Standard Model (Electroweak Gauge Theory (W, Z, Top, etc.)
Supporting papers:
Notes:Paper will be sent later
The pair production of Z bosons is studied using the data collected by the L3 detector at LEP in e+e- interactions at centre-of-mass energy from 183 GeV up to 202 GeV corresponding to 460 pb^-1 of integrated luminosity. The cross sections of this process are measured at each centre-of-mass. Moreover is investigated the rate of ZZ events with b-quark content and their cross section is measured. A search for anomalous triple neutral gauge boson couplings, forbidden in the Standard Model, is performed. No evidence for those couplings is found and limits on their values are set.
Authors:L3 Collaboration
Proposed speaker: L3 speaker
Contact person:Simonetta Gentile
(CERN),
Simonetta.Gentile@cern.ch
Sessions: PA-05 Tests of the Electroweak Gauge Theory / PL-06a Precision Tests of the Standard Model (Electroweak Gauge Theory (W, Z, Top, etc.)
Supporting papers:
Notes:in preparation
Anomalous ZZgamma and Zgammagamma couplings are studied in the process e+e- -> Zgamma using the data sample collected by the L3 detector , at centre-of-mass energies between 192 and 202 GeV corresponding to an integrated luminosity of 233 pb-1. The cross section for Zgamma production is also measured. This cross section is found to be in good agreement with the Standard Model prediction. No evidence for anomalous couplings is found and limits are derived .
Authors:L3 Collaboration
Proposed speaker: L3 speaker
Contact person:Simonetta Gentile
(CERN),
Simonetta.Gentile@cern.ch
Sessions: PA-05 Tests of the Electroweak Gauge Theory / PL-06a Precision Tests of the Standard Model (Electroweak Gauge Theory (W, Z, Top, etc.)
Supporting papers:
Notes:in preparation 5/12/00 TY-Moved from PL7a to PL6a, and from PA11 to PA5.
The process e+e- -> Zgammagamma is studied at centre of mass energies above the Z pole with a corresponding integrated luminosity of approximatly 490 pb-1. The first measurement of the cross section at different centre-of-mass energy is performed , using a sample of hadronic events with two isolated high energy photons. Limits on anomlous quartic gauge boson coupling are derived. This process allows to put most stringent direct limits on the parameters a_0 and a_c are derived.
Authors:L3 Collaboration
Proposed speaker: L3 speaker
Contact person:Simonetta Gentile
(CERN),
Simonetta.Gentile@cern.ch
Sessions: PA-05 Tests of the Electroweak Gauge Theory / PL-06a Precision Tests of the Standard Model (Electroweak Gauge Theory (W, Z, Top, etc.)
Supporting papers:
Notes:in preparation
The process e+ e- -> n gamma, with n>= 2, is studied using the data sample collected by the L3 detector at centre-of-mass energies between 192 and 202 GeV, corresponding to an integrated luminosity of 233 pb-1. The observed distributions and the measured cross section are in good agreement with the Standard Model expectations. This is used to set limits on the QED cut-off parameters and the mass of excited electrons.
Authors:L3 Collaboration
Proposed speaker: L3 speaker
Contact person:Simonetta Gentile
(CERN),
Simonetta.Gentile@cern.ch
Sessions: PA-05 Tests of the Electroweak Gauge Theory / PL-06a Precision Tests of the Standard Model (Electroweak Gauge Theory (W, Z, Top, etc.)
Supporting papers:
Notes:in preparation
We investigate Bose-Einstein correlations in W-pair production with the L3 detector at LEP at center-of-mass energies at or above 189 GeV. In particular, we investigate Bose-Einstein correlations in W+W- overlap and the possible existence of these correlations between particles coming from different W's, which may influence the W mass measurements in the fully-hadronic channel e+e- -> W+W- -> qqqq. The results are preliminary.
Authors:L3 Collaboration
Proposed speaker: L3 speaker
Contact person:Simonetta Gentile
(CERN),
Simonetta.Gentile@cern.ch
Sessions: PA-05 Tests of the Electroweak Gauge Theory / PL-06a Precision Tests of the Standard Model (Electroweak Gauge Theory (W, Z, Top, etc.)
Supporting papers:
Notes:in preparation
We report on preliminary studies of colour reconnection effects in hadronic decays of W pairs with the L3 detector at centre-of-mass energy at or above 189 GeV. The analysis is based on a comparison of charged particle multiplicities in qqqq and qqln events, and on the study of the particle and energy flow between jets associated to the same W boson and between two different W bosons in qqqq events. The interjet activity shows some sensitivity to hadronisation models incorporating colour reconnection schemes which are not excluded up to now from other studies.
Authors:L3 Collaboration
Proposed speaker: L3 speaker
Contact person:Simonetta Gentile
(CERN),
Simonetta.Gentile@cern.ch
Sessions: PA-05 Tests of the Electroweak Gauge Theory / PL-06a Precision Tests of the Standard Model (Electroweak Gauge Theory (W, Z, Top, etc.)
Supporting papers:
Notes:in preparation
We report on the measurement of W-boson pair-production with the L3 detector at LEP. In a data sample corresponding to a total luminosity of 233 pb-1 collected at centre-of-mass energies of 192, 196, 200 and 202 GeV, we select 3529 four-fermion events with pairs of hadronic jets or pairs of leptons with high invariant masses. Branching fractions of W decays into different fermion-antifermion pairs are determined. Assuming charged-current lepton universality, the branching fraction for hadronic W decays is measured including data collected at lower centre-of-mass energies. Combining all final states the total cross section for W-pair production is measured at the four centre-of-mass energies. These results are preliminary.
Authors:L3 Collaboration
Proposed speaker: L3 speaker
Contact person:Simonetta Gentile
(CERN),
Simonetta.Gentile@cern.ch
Sessions: PA-05 Tests of the Electroweak Gauge Theory / PL-06a Precision Tests of the Standard Model (Electroweak Gauge Theory (W, Z, Top, etc.)
Supporting papers:
Notes:in preparation
Preliminary results of the W+- bosons helicity fractions, using the data collected at centre-of-mass energies of 192 - 202 GeV,corresponding to an integrated luminosity of 233 pb-1 are presented. The fraction of longitudinally polarised W bosons is measured, and the result is combined with the published data at center-of-mass energies of 183 GeV and 189 GeV. Furthermore, the combined data demonstrate clearly the variation of the W helicity fractions with the W polar scattering angle. The helicity information is used to study WW spin correlations.
Authors:L3 Collaboration
Proposed speaker: L3 speaker
Contact person:Simonetta Gentile
(CERN),
Simonetta.Gentile@cern.ch
Sessions: PA-05 Tests of the Electroweak Gauge Theory / PL-06a Precision Tests of the Standard Model (Electroweak Gauge Theory (W, Z, Top, etc.)
Supporting papers:
Notes:in preparation
We report on measurements of the mass and total decay width of the W boson with the L3 detector at LEP. W-pair events produced in e+e- interactions between 161 GeV and 202 GeV centre-of-mass energy are selected in a data sample corresponding to a total luminosity of approximatly 490 pb-1. Combining all final states in W-pair production, the mass and total decay width of the W boson are determined. These results are preliminary.
Authors:L3 Collaboration
Proposed speaker: L3 speaker
Contact person:Simonetta Gentile
(CERN),
Simonetta.Gentile@cern.ch
Sessions: PA-05 Tests of the Electroweak Gauge Theory / PL-06a Precision Tests of the Standard Model (Electroweak Gauge Theory (W, Z, Top, etc.)
Supporting papers:
Notes:in preparation
A preliminary measurement of the cross section for the process e+e- -> W+W-gamma is presented using data collected with the L3 detector at centre-of-mass-energy at or above 189 GeV. Selecting W+W- events containing an isolated photon the cross section, defined within kinematic cuts imposed on the photon, is measured. Limits on Anomalous Quartic Couplings are derived at 95\% confidence level and combined with those obtained from nunugammagamma production. These results are preliminary.
Authors:L3 Collaboration
Proposed speaker: L3 speaker
Contact person:Simonetta Gentile
(CERN),
Simonetta.Gentile@cern.ch
Sessions: PA-05 Tests of the Electroweak Gauge Theory / PL-06a Precision Tests of the Standard Model (Electroweak Gauge Theory (W, Z, Top, etc.)
Supporting papers:
Notes:in preparation
Single W boson production in electron-positron collisions is analysed with the L3 detector at LEP. The data sample collected at a centre-of-mass energies of sqrt(s) = 192 GeV, 196 GeV, 200 GeV and 202 GeV corresponds to an integrated luminosity of 233 pb-1. Events with a single energetic lepton or two hadronic jets visible in the detector are selected. The total cross-sections are measured and found to be consistent with the Standard Model expectation. Including our single W boson results obtained at lower sqrt(s) the WWgamma gauge couplings kappa-gamma and lambda-gamma are determined. The results are preliminary.
Authors:L3 Collaboration
Proposed speaker: L3 speaker
Contact person:Simonetta Gentile
(CERN),
Simonetta.Gentile@cern.ch
Sessions: PA-05 Tests of the Electroweak Gauge Theory / PL-06a Precision Tests of the Standard Model (Electroweak Gauge Theory (W, Z, Top, etc.)
Supporting papers:
Notes:in preparation
We report preliminary results on the measurement of triple-gauge-boson couplings of the W boson in e+e- collisions at 192 <= sqrt(s) <= 202 GeV. Using W-pair events selected in a data sample corresponding to a total luminosity of 233 pb-1 collected by the L3 detector at LEP during the 1999 data taking period, we measure the C- and P-conserving couplings g1Z, kappa-gamma and lambda-gamma, assuming gauge invariance relations between WWZ and WWgamma couplings, and the C- and P-violating but CP-conserving coupling g5Z. Preliminary results are combined with other final states and our previous results based on the data collected in 1998 and earlier.
Authors:L3 Collaboration
Proposed speaker: L3 speaker
Contact person:Simonetta Gentile
(CERN),
Simonetta.Gentile@cern.ch
Sessions: PA-05 Tests of the Electroweak Gauge Theory / PL-06a Precision Tests of the Standard Model (Electroweak Gauge Theory (W, Z, Top, etc.)
Supporting papers:
Notes:in preparation
Small-angle Bhabha scattering data recorded at the Z resonance and large angle Bhabha scattering data recorded at sqrt(s)=189 GeV by the L3 detector at LEP are used to measure the running of the effictive fine-structure constant for spacelike momentum transfers. The results are in agreement with theoretical predicions.
Authors:L3 Collaboration
Proposed speaker: L3 speaker
Contact person:Simonetta Gentile
(CERN),
Simonetta.Gentile@cern.ch
Sessions: PA-05 Tests of the Electroweak Gauge Theory / PL-06a Precision Tests of the Standard Model (Electroweak Gauge Theory (W, Z, Top, etc.)
Supporting papers: L3 Collaboration, M. Acciarri et al., Physics letters B Accepted CERN-EP/2000-005, 06 January 2000. L3 preprint 197. Measurement of the Running of the Fine-Structure Constant.
Notes:
We report on measurements of hadronic and leptonic cross sections and leptonic forward-backward asymmetries performed with the L3 detector in the years 1993-95. A total luminosity of 103 pb-1 was collected at centre-of-mass energies around 91 GeV which corresponds to 2.5 million hadronic and 245 thousand leptonic events selected. These data lead to a significantly improved determination of Z parameters. From the total cross sections, combined with our measurements in 1990-92, we obtain the final results for the mass and total withs of the Z as well as the partial witdhs into leptons and hadrons. From the invisible width we determine in the Standard Model the number of light neutrino species. Adding our results on the leptonic forward-backward asymmetries and the tau polarisation, the effective vector and axial-vector coupling constants of the neutral weak current to charged leptons are determined. Including our measurements of the Z -> b bbar forward-backward and quark charge asymmetries the effective electroweak mixing angle is derived. All these measurements are in good agreement with the Standard Model of electroweak interactions. Using all our measurements of electroweak observables an upper limit on the mass of the Standard Model Higgs boson of 133 GeV is set at 95% confidence level.
Authors:L3 Collaboration
Proposed speaker: L3 speaker
Contact person:Simonetta Gentile
(CERN),
Simonetta.Gentile@cern.ch
Sessions: PA-05 Tests of the Electroweak Gauge Theory / PL-06a Precision Tests of the Standard Model (Electroweak Gauge Theory (W, Z, Top, etc.)
Supporting papers: European Physical Journal C accepted. CERN-EP/2000-022, 04 February 2000. L3 preprint 202. Measurements of Cross Sections and Forward-Backward Asymmetries at the Z Resonance and Determination of Electroweak Parameters.
Notes:
In this note we present preliminary measurements of e+e- annihilation into hadrons and leptons pairs. The data have been collected with L3 detector at LEP at centre-of-mass energies between 130 and 200 GeV, corresponding to a total integrated of approximatly 490 pb-1. The measurements of total hadronic and leptonic cross sections and leptonic forward-backward asymmetries are performed. Published data are combined with recent preliminary results. The measurements are interpreted in the S--Matrix framework.
Authors:L3 Collaboration
Proposed speaker: L3 speaker
Contact person:Simonetta Gentile
(CERN),
Simonetta.Gentile@cern.ch
Sessions: PA-05 Tests of the Electroweak Gauge Theory / PL-06a Precision Tests of the Standard Model (Electroweak Gauge Theory (W, Z, Top, etc.)
Supporting papers:
Notes:in preparation
We report on measurements of quasi-real Compton scattering at centre-of-mass energies between 20 GeV and 180 GeV, using the L3 detector at LEP. The analysis is based on data collected between 1991 and 1999. The measured differential and total cross sections are in good agreement with their QED expectations. They are used to derive upper limits on the coupling, lambda, for the on-shell production of an excited electron, e*, decaying radiatively into e gamma.
Authors:L3 Collaboration
Proposed speaker: L3 speaker
Contact person:Simonetta Gentile
(CERN),
Simonetta.Gentile@cern.ch
Sessions: PA-05 Tests of the Electroweak Gauge Theory / PL-06a Precision Tests of the Standard Model (Electroweak Gauge Theory (W, Z, Top, etc.)
Supporting papers:
Notes:in preparation
Measurements of the W boson pair production cross section and W decay branching fractions are obtained from e+e- collisions at centre-of-mass energies between 161 and 202 GeV.
Authors:The OPAL collaboration
Proposed speaker:
Contact person:David J Miller
(CERN),
dave.miller@cern.ch
Sessions: PA-05 Tests of the Electroweak Gauge Theory / PL-06a Precision Tests of the Standard Model (Electroweak Gauge Theory (W, Z, Top, etc.)
Supporting papers:
Notes:
The mass and width of the W boson are measured using the Opal detector at LEP. Results are obtained from approximately 500 pb-1 of data recorded at centre-of-mass energies of between 161-202 GeV.
Authors:The OPAL collaboration
Proposed speaker:
Contact person:David J Miller
(CERN),
dave.miller@cern.ch
Sessions: PA-05 Tests of the Electroweak Gauge Theory / PL-06a Precision Tests of the Standard Model (Electroweak Gauge Theory (W, Z, Top, etc.)
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 PN422 at http://opal.web.cern.ch/Opal/pubs/physnote/html/pn422.html
Notes:
The production cross sections for the W+W- gamma, qq gamma gamma and nu nu gamma gamma final states are measured in e+e- collisions at centre-of-mass energies 183-202 GeV with the Opal detector at LEP. The cross sections and angular distributions are used to place limits on anomalous WWgg and ZZgg quartic gauge couplings.
Authors:The OPAL collaboration
Proposed speaker:
Contact person:David J Miller
(CERN),
dave.miller@cern.ch
Sessions: PA-05 Tests of the Electroweak Gauge Theory / PL-06a Precision Tests of the Standard Model (Electroweak Gauge Theory (W, Z, Top, etc.)
Supporting papers: To be submitted to the conference and listed on http://opal.web.cern.ch/Opal/pubs/publications.html Results at 189 GeV available as CERN-EP/99-130, Phys. Lett. B471 (1999) 293-307 =http://opal.web.cern.ch/Opal/pubs/paper/html/pr292.html
Notes:
Measurements of the event properties of hadronically decaying Ws in W+W- events observed in the OPAL detector at LEP will be presented. In addition to studies of charged particle multiplicity, fragmentation functions and rapidity, observables based on the particle flow will also be presented and compared with models of colour reconnection. The predicted effect of colour reconnection on OPAL measurements of M_W is also quantified in the context of models studied.
Authors:The OPAL collaboration
Proposed speaker:
Contact person:David J Miller
(CERN),
dave.miller@cern.ch
Sessions: PA-05 Tests of the Electroweak Gauge Theory / PL-06a Precision Tests of the Standard Model (Electroweak Gauge Theory (W, Z, Top, etc.)
Supporting papers: To be submitted to the conference and listed on http://opal.web.cern.ch/Opal/pubs/publications.html Results at 183 GeV available as CERN-EP/98-196, Phys. Lett. B453 (1999) 153-168 =http://opal.web.cern.ch/Opal/pubs/paper/html/pr267.html Results at 189 GeV available as OPAL Physics Note PN417 =http://opal.web.cern.ch/Opal/pubs/physnote/html/pn417.html Study using heavy particle production in OPAL Physics Note PN412 =http://opal.web.cern.ch/Opal/pubs/physnote/html/pn412.html
Notes:
Measurements of Bose-Einstein correlations in hadronically decaying Ws in W+W- events observed in the OPAL detector at LEP are performed using data recorded at centre-of-mass energies between 172-202 GeV. The correlations are studied separately in the semi-leptonic (qqlv) and fully-hadronic (qqqq) final states. Particular emphasis is placed on the question of the existance of Bose-Einstein correlations between pions from the decays of different W bosons in qqqq events.
Authors:The OPAL collaboration
Proposed speaker:
Contact person:David J Miller
(CERN),
dave.miller@cern.ch
Sessions: PA-05 Tests of the Electroweak Gauge Theory / PL-06a Precision Tests of the Standard Model (Electroweak Gauge Theory (W, Z, Top, etc.)
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 PN393 =http://opal.web.cern.ch/Opal/pubs/physnote/html/pn393.html
Notes:
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-05 Tests of the Electroweak Gauge Theory / PL-06a Precision Tests of the Standard Model (Electroweak Gauge Theory (W, Z, Top, etc.)
Supporting papers: To be submitted to the conference and listed on http://opal.web.cern.ch/Opal/pubs/publications.html
Notes:Of greater interest to Parallel session 11, Search for new particles and phenomena and to Plenary session 7a, Search for new particles and new phenomena? 5/15/00 TY-PA-05,PL-06a are the second choice. The first choice is selected in abstract #578.
A preliminary analysis of the data collected in 1999 with the DELPHI detector at e+e- collision energy between 192 and 202 GeV was performed in order to extract the hadronic and leptonic cross-sections, as well as the leptonic forward-backward asymmetries. Various interpretations of the results, including possible physics beyond the Standard Model, are presented. In particular, the data are used to investigate potential contact interactions, the exchange of sneutrinos in R-parity violating SUSY and for Z' bosons and search for the existence of gravity in extra dimensions.
Authors:DELPHI Collaboration
Proposed speaker:
Contact person:Clara Matteuzzi
(),
Clara.Matteuzzi@cern.ch
Sessions: PA-05 Tests of the Electroweak Gauge Theory / PL-06a Precision Tests of the Standard Model (Electroweak Gauge Theory (W, Z, Top, etc.)
Supporting papers:
Notes:Paper will be sent later
The cross-section ratio R_f=sigma_ffbar/sigma_had and the forward-backward asymmetry A^f_fb for heavy flavours produced in the reaction e+e-->Z/gamma*-->ffbar have been measured with the DELPHI detector, at LEP collision energies of 183 GeV and higher. The quark flavours are separated using a tagging variable, the main ingredients of which are the lifetime and secondary vertex information provided by the DELPHI 3-layer microvertex detector. High purity selections are made from which R_f and A^f_fb are measured. The results are compared to the predictions of the Standard Model.
Authors:DELPHI Collaboration
Proposed speaker:
Contact person:Clara Matteuzzi
(),
Clara.Matteuzzi@cern.ch
Sessions: PA-05 Tests of the Electroweak Gauge Theory / PL-06a Precision Tests of the Standard Model (Electroweak Gauge Theory (W, Z, Top, etc.)
Supporting papers:
Notes:Paper will be sent later
During 1993 and 1995 LEP was run at 3 energies near the Z$^0$ peak in order to give improved measurements of the mass and width of the resonance. During 1994, LEP operated only at the Z0 peak. In total DELPHI accumulated data corresponding to an integrated luminosity of approximately 116 pb-1. Analyses of the hadronic cross-sections and of the cross-sections and forward-backward asymmetries in the leptonic channels used the most precise evaluations of the LEP energies. In the dimuon channel, events with a photon radiated from the initial state have been used to probe the cross-sections and asymmetries down to PETRA energies. Model independent fits to all DELPHI lineshape and asymmetry data from 1990 to 1995 have been carried out giving values of the resonance parameters: M_Z = 91.1863+-0.0028 GeV G_Z = 2.4876+-0.0041 GeV sigma_0 = 41.578+-0.069 nb R_l = 20.730+-0.060 Afbzero = 0.0187+-0.0019. These values are significantly more precise than those previously published. The results are interpreted in terms of the Standard Model.
Authors:DELPHI Collaboration
Proposed speaker:
Contact person:Clara Matteuzzi
(),
Clara.Matteuzzi@cern.ch
Sessions: PA-05 Tests of the Electroweak Gauge Theory / PL-06a Precision Tests of the Standard Model (Electroweak Gauge Theory (W, Z, Top, etc.)
Supporting papers:
Notes:Paper will be sent later
A test of the QED process e+e- --> g+g+(g) is reported. The data were collected by the DELPHI detector up to July 2000 at the highest energies achieved at LEP. The differential and total cross-sections for the process e+e- --> g g were measured. 95% Confidence Level (C.L.) upper limits on the deviations from the Born differential cross-section were derived, resulting in lower bounds on the QED cut-off parameters, Lambda, on the mass of an excited electron, M(e*) (for lambda_g =1), and on the string mass scale, M_s.
Authors:DELPHI Collaboration
Proposed speaker:
Contact person:Clara Matteuzzi
(),
Clara.Matteuzzi@cern.ch
Sessions: PA-05 Tests of the Electroweak Gauge Theory / PL-06a Precision Tests of the Standard Model (Electroweak Gauge Theory (W, Z, Top, etc.)
Supporting papers:
Notes:Paper will be sent later
Double radiative return events to the Z, where the two photons radiated have similar energies were studied at LEP at centre-of-mass energies ranging from 189 GeV to values exceeding 200 GeV. The three possible photon topologies have been studied: those where both photons are within the detector acceptance, those where one of the photons is lost in the beam-pipe and finally those where both photons are lost in the beam-pipe. For the first time at LEP, the cross-section for this process has been measured and confronted to theoretical predictions.
Authors:DELPHI Collaboration
Proposed speaker:
Contact person:Clara Matteuzzi
(),
Clara.Matteuzzi@cern.ch
Sessions: PA-05 Tests of the Electroweak Gauge Theory / PL-06a Precision Tests of the Standard Model (Electroweak Gauge Theory (W, Z, Top, etc.)
Supporting papers:
Notes:Paper will be sent later
A preliminary analysis of fermion-pair production using data collected in 2000 with the DELPHI detector in e+e- collisions at energies of 200 GeV and above is presented.
Authors:DELPHI Collaboration
Proposed speaker:
Contact person:Clara Matteuzzi
(),
Clara.Matteuzzi@cern.ch
Sessions: PA-05 Tests of the Electroweak Gauge Theory / PL-06a Precision Tests of the Standard Model (Electroweak Gauge Theory (W, Z, Top, etc.)
Supporting papers:
Notes:Paper will be sent later
Preliminary results on cross sections and forward-backward asymmetries for hadronic and leptonic events produced in e+e- collisions at centre-of-mass energies from 192 to 202 GeV are given. These results combined with previous results obtained at lower energies lead to constraints upon physics beyond the Standard Model such as four-fermion contact interactions, leptoquarks, Z' bosons, R-parity violating squarks and sneutrinos, and TeV scale quantum gravity.
Authors:ALEPH collaboration
Proposed speaker:
Contact person:Fabrizio Palla
(CERN),
Fabrizio.Palla@cern.ch
Sessions: PA-05 Tests of the Electroweak Gauge Theory / PL-06a Precision Tests of the Standard Model (Electroweak Gauge Theory (W, Z, Top, etc.)
Supporting papers:
Notes:
The cross sections for the single resonant production of intermediate vector bosons were measured using the 52 and 154 pb^-1 integrated luminosities collected by the DELPHI experiment at centre-of-mass energy of 183 and 189 GeV respectively. Both charged and neutral boson productions were investigated and both hadronic and leptonic decays of the bosons were analyzed. Cross sections were defined topologically by kinematical cuts. Preliminary cross section measurements at centre-of-mass energy ranging from 192 to 202 GeV are also presented. In the case of single-W production (e+e- -> e nu W) a new signal definition, common to the four LEP experiments to allow for combination of the results, was used. Also the 189 GeV data were reinterpreted according to this new definition. The obtained values for the cross sections are in agreement with the predictions of the Standard Model.
Authors:DELPHI Collaboration
Proposed speaker:
Contact person:Clara Matteuzzi
(),
Clara.Matteuzzi@cern.ch
Sessions: PA-05 Tests of the Electroweak Gauge Theory / PL-06a Precision Tests of the Standard Model (Electroweak Gauge Theory (W, Z, Top, etc.)
Supporting papers:
Notes:Paper will be sent later
A Measurement of the W mass and W Width has been performed by the DELPHI Collaboration. Results are presented on the data collected by the experiment during 1998 and 1999 and combined with previously published results. The 1998 data sample has an integrated luminosity of 155 pb-1 and an average centre of mass energy of 188.6 GeV. The 1999 data sample has an integrated luminosity of 230 pb-1 and was collected at centre of mass energies between 191 GeV and 202 GeV. The results presented here on the 1998 data sample will shortly be sent for publication, whereas the 1999 results are preliminary.
Authors:DELPHI Collaboration
Proposed speaker:
Contact person:Clara Matteuzzi
(),
Clara.Matteuzzi@cern.ch
Sessions: PA-05 Tests of the Electroweak Gauge Theory / PL-06a Precision Tests of the Standard Model (Electroweak Gauge Theory (W, Z, Top, etc.)
Supporting papers:
Notes:Paper will be sent later
Results on the measurement of four-fermion final states originating from on-shell ZZ production, obtained using data collected by DELPHI in 1997, 1998 and 1999, at centre of mass energies ranging from 183 to 202 GeV, are presented. The results from the 1999 data (192-202 GeV) are still preliminary. The principal final states q qbar q qbar, mu+ mu- q qbar, e+ e- q qbar, nu nubar q qbar, l+ l- l+ l-, and nu nubar l+ l- are used. The cross-sections and angular distributions measured in individual sub-channels are combined and compared with the latest model predictions. Preliminary limits on anomalous neutral-current triple gauge couplings derived from these measurements are given.
Authors:DELPHI Collaboration
Proposed speaker:
Contact person:Clara Matteuzzi
(),
Clara.Matteuzzi@cern.ch
Sessions: PA-05 Tests of the Electroweak Gauge Theory / PL-06a Precision Tests of the Standard Model (Electroweak Gauge Theory (W, Z, Top, etc.)
Supporting papers:
Notes:Paper will be sent later
The measurements of R_b = sigma(e+e- -> bb)/sigma(e+e- -> qq) and of the b quark forward-backward charge asymmetry, A_{fb}^{b}, at centre-of-mass energies above the Z pole are described. The measurement of R_b is performed at sqrt{s} above 130 GeV using a b-tagging method that exploits the relatively large decay length of b-hadrons. The measurement of A_{fb}^{b} is performed using the large statistics event sample collected at sqrt{s}=189 GeV with a lepton--tag analysis based on the selection of prompt muons and electrons. The results at sqrt{s}=189 GeV are: R_b = 0.163 +- 0.013(stat.) +- 0.005(syst.), A_{fb}^{b} = $0.61 +- 0.18(stat.) +- 0.09(syst.).
Authors:L3 Collaboration
Proposed speaker: L3 speaker
Contact person:Simonetta Gentile
(CERN),
Simonetta.Gentile@cern.ch
Sessions: PA-05 Tests of the Electroweak Gauge Theory / PL-06a Precision Tests of the Standard Model (Electroweak Gauge Theory (W, Z, Top, etc.)
Supporting papers:
Notes:in preparation
We present a combined measurement of Rb = Gamma(Z -> bb) / Gamma(Z -> hadrons}) and the semileptonic branching ratio of b quarks in Z decays, Br(b->lnuX), using double-tag methods. Two analyses are performed on one million hadronic Z decays collected in 1994 and 1995. The first analysis exploits the capabilities of the silicon microvertex detector. The tagging of b-events is based on the large impact parameter of tracks from weak b-decays with respect to the e+e- collision point. In the second analysis, a high-pt lepton tag is used to enhance the b-component in the sample and its momentum spectrum is used to constrain the model dependent uncertainties in the semileptonic b-decay. The analyses are combined in order to provide precise determinations of Rb and Br(b->lnuX): Rb = 0.2174 +- 0.0015(stat.) +- 0.0028(sys.); Br(b->lnuX) = (10.16 +- 0.13(stat.) +- 0.30(sys.))%.
Authors:L3 Collaboration
Proposed speaker: L3 speaker
Contact person:Simonetta Gentile
(CERN),
Simonetta.Gentile@cern.ch
Sessions: PA-05 Tests of the Electroweak Gauge Theory / PL-06a Precision Tests of the Standard Model (Electroweak Gauge Theory (W, Z, Top, etc.)
Supporting papers: L3 Collab., M. Acciarri et al., European Physical Journal C 13/1, 47-61 (2000) CERN-EP/99-121, 27 August 1999. L3 preprint 185. Measurement of Rb and Br (b->lnuX) at LEP Using Double-Tag Methods.
Notes:
We present a measurement of the left-right cross-section asymmetry (ALR) for Z boson production by e+e- collisions. The measurement includes the final data taken with the SLD detector at the SLAC Linear Collider (SLC) during the period 1996-1998. Using a sample of 383,487 Z decays collected during the 1996-1998 runs we measure the pole-value of the asymmetry, ALR0, to be 0.15056+-0.00239 which is equivalent to an effective weak mixing angle of sin2th(eff) = 0.23107+-0.00030. Our result for the complete 1992-1998 dataset comprising 537 thousand Z decays is sin2th(eff) = 0.23097+-0.00027.
Authors:SLD Collaboration
Proposed speaker:
Contact person:Peter C. Rowson
(SLAC),
rowson@slac.stanford.edu
Sessions: PA-05 Tests of the Electroweak Gauge Theory / PL-06a Precision Tests of the Standard Model (Electroweak Gauge Theory (W, Z, Top, etc.)
Supporting papers: SLAC-PUB-8401, April, 2000.
Notes:
We report new direct measurements of the Z0-lepton coupling asymmetry parameters A_e, A_mu and A_tau, with the complete sample of polarized Z0's collected by the SLD detector at the SLAC Linear Collider. The parameters are extracted from the measurement of the left-right and left-right-forward-backward asymmetries for each lepton species. The 1996 data and the 1997-1998 data with upgraded tracking acceptance are included in this analysis and combined with published data from the 1993-95 runs. Assuming lepton universality, we measured the lepton asymmetry parameter with a precision of 0.0053 (preliminary).
Authors:SLD Collaboration
Proposed speaker:
Contact person:Toshii Abe
(SLAC),
toshi@slac.stanford.edu
Sessions: PA-05 Tests of the Electroweak Gauge Theory / PL-06a Precision Tests of the Standard Model (Electroweak Gauge Theory (W, Z, Top, etc.)
Supporting papers:
Notes:
The measurement of the mass of the W boson, m_W, at LEP2 relies on a kinematic fit which uses the beam energy, E_b, as a constraint. The statistical precision from the complete LEP2 data set will be such that E_b should be known to ~15 MeV or better in order not to be a dominant uncertainty. Such a small error is not achievable with the established magnetic extrapolation method of energy determination at LEP2. Improved precision is expected from the LEP spectrometer project, which began operation in 1999, and from analysis of machine observables which are sensitive to the synchrotron energy loss. Recent results are presented from all of these approaches, and their prospects assessed.
Authors:The LEP energy calibration group
Proposed speaker: Dr Peter Renton
Contact person:Guy Wilkinson
(CERN),
g.wilkinson@cern.ch
Sessions: PA-05 Tests of the Electroweak Gauge Theory / PL-06a Precision Tests of the Standard Model (Electroweak Gauge Theory (W, Z, Top, etc.)
Supporting papers:
Notes:
We present a preliminary measurement of the Z0 boson to b and c quark production fractions Rb and Rc, using the 96-98 SLD data sample of 400K hadronic Z0 decays. We extract Rb and Rc simultaneously using a multi-tag method. This measurements relies on the unique features of the SLD experiment, the high resolution CCD vertex detector and the micron size beam spot. This analysis uses improved tagging algorithms and most of the tagging efficiencies are measured from data to reduce systematic errors.
Authors:SLD Collaboration
Proposed speaker:
Contact person:Dong Su
(Stanford Linear Accelerator Center),
sudong@slac.stanford.edu
Sessions: PA-05 Tests of the Electroweak Gauge Theory / PL-06a Precision Tests of the Standard Model (Electroweak Gauge Theory (W, Z, Top, etc.)
Supporting papers:
Notes:
We present a direct measurement of the parity violation parameters Ab and Ac from the decay of polarized Z0 into b and c quarks. Ab and Ac are derived from the left-right forward-backward asymmetry of b and c quarks tagged via leptons from semileptonic decays. The lepton identification algorithm combines information from tracking, calorimetry and from the SLD Cherenkov Ring Imaging Detector. The values of Ab and Ac are extracted using a maximum likelihood fit to the differential cross section for fermion production. Vertexing information and decay kinematics have been used to discriminate among the different sources of tagged leptons. A new treatment of mixing effects and of background contamination has been introduced and a new vertexing algorithm has been used in the muon analysis. Based on the full 1993-1998 SLD data sample of 550K hadronic Z0 decays with highly polarized electron beams, we have measured Ab (Ac) with a ~3% (~5%) statistical error.
Authors:SLD Collaboration
Proposed speaker:
Contact person:Dong Su
(Stanford Linear Accelerator Center),
sudong@slac.stanford.edu
Sessions: PA-05 Tests of the Electroweak Gauge Theory / PL-06a Precision Tests of the Standard Model (Electroweak Gauge Theory (W, Z, Top, etc.)
Supporting papers:
Notes:
We present an improved SLD measurement of the parity-violating parameter Ab from Left-Right Forward-Backward asymmetry of b b-bar pair production at the Z0 pole. We take advantage of the high polarization of the SLC electron beam and use a jet-charge self-calibrating technique. A high purity b-tag based on topological reconstruction of the mass of B-decay vertex is used in the measurement.
Authors:SLD Collaboration
Proposed speaker:
Contact person:Dong Su
(Stanford Linear Accelerator Center),
sudong@slac.stanford.edu
Sessions: PA-05 Tests of the Electroweak Gauge Theory / PL-06a Precision Tests of the Standard Model (Electroweak Gauge Theory (W, Z, Top, etc.)
Supporting papers:
Notes:
We present preliminary measurements of the parity-violation parameters Ab and Ac at the Z pole. These measurements include the data taken with the SLD detector at the SLAC Linear Collider (SLC) during the period 1996-98. Heavy flavor events are selected with high efficiency and purity using the invariant mass of displaced vertices, identified with the SLD precision CCD vertex detector. Two methods are used for quark/antiquark discrimination. One uses the net charge of the displaced vertex. The second uses the charge of tracks in the displaced vertex which are identified as kaons by the SLD Cherenkov Ring Imaging Detector (CRID). The signal purities and analyzing powers are calibrated from the data to reduce the systematic errors. The parameter Ab (Ac) is determined with a statistical uncertainty of better than 0.02 (0.03).
Authors:SLD Collaboration
Proposed speaker:
Contact person:Dong Su
(Stanford Linear Accelerator Center),
sudong@slac.stanford.edu
Sessions: PA-05 Tests of the Electroweak Gauge Theory / PL-06a Precision Tests of the Standard Model (Electroweak Gauge Theory (W, Z, Top, etc.)
Supporting papers:
Notes:
We present a direct measurement of the Z0 to cc-bar coupling parity-violation parameter Ac with the SLD detector. The measurement is based on the entire SLD data sample of 530k hadronic Z0 decays, produced with a mean electron-beam polarization of Pe = 73%. The tagging of c-quark events was performed using two methods: the exclusive reconstruction of D*+, D+, and D0 mesons, and the inclusive PT spectrum of soft-pions (pi_s) in the decay of D*+ -> D0 pi_s+. The combination of these two methods yields a precision of +-0.040.
Authors:SLD Collaboration
Proposed speaker:
Contact person:Dong Su
(Stanford Linear Accelerator Center),
sudong@slac.stanford.edu
Sessions: PA-05 Tests of the Electroweak Gauge Theory / PL-06a Precision Tests of the Standard Model (Electroweak Gauge Theory (W, Z, Top, etc.)
Supporting papers:
Notes:
We have made the first direct measurement of the parity-violating coupling of the Z0 boson to the strange quark, A_s, using 550,000 e+e- -> Z0 -> hadrons events produced with a polarized electron beam and recorded by the SLD experiment. Z0->s-sbar events were tagged by the absence of B or D hadrons and the presence in each hemisphere of a high-momentum K+- or K0s. From the polar angle distributions of the strangeness-signed thrust axis, we obtained A_s = 0.895+-0.066(stat.)+-0.063(syst.). The analyzing power and u-ubar+d-dbar background were estimated from the data.
Authors:SLD Collaboration
Proposed speaker:
Contact person:Dong Su
(Stanford Linear Accelerator Center),
sudong@slac.stanford.edu
Sessions: PA-05 Tests of the Electroweak Gauge Theory / PL-06a Precision Tests of the Standard Model (Electroweak Gauge Theory (W, Z, Top, etc.)
Supporting papers:
Notes:
Using e+e- ---> di-fermion events radiative to the Z pole, DELPHI has reconstructed the energy of the beams using energy and momentum constraints and a reweighting technique. The preliminary results are compared to the energies measured by the collider using other techniques.
Authors:DELPHI Collaboration
Proposed speaker:
Contact person:Clara Matteuzzi
(Universita di Milano),
Clara.Matteuzzi@cern.ch
Sessions: PA-05 Tests of the Electroweak Gauge Theory / PL-06a Precision Tests of the Standard Model (Electroweak Gauge Theory (W, Z, Top, etc.)
Supporting papers:
Notes:Contributed paper will follow
The most general Lorentz invariant triple boson coupling between W and Zo bosons allows a parity violating coupling. Based on results from the LEP measurements of the coupling deltagz, we obtain constraints on the parity violating coupling z_Z.
Authors:Peter Fisher, Yoshi Uchida
Proposed speaker: Peter Fisher, Yoshi Uchida
Contact person:Peter H Fisher
(MIT),
fisherp@mit.edu
Sessions: PA-05 Tests of the Electroweak Gauge Theory / PL-06a Precision Tests of the Standard Model (Electroweak Gauge Theory (W, Z, Top, etc.)
Supporting papers:
Notes:
The results of the W pair production cross section measurements at the LEP II experiments are used to obtain a measurement of the invisible decay width of the W boson. Such an invisible decay width, resulting from W decay channels that have event signatures that are not consistent with any Standard Model decay, would lower the observed cross section compared to that of the Standard Model. From the LEP combined result from the 183 GeV data gathered in 1997, we obtain an upper limit of 45 MeV at 95\% CL.
Authors:Peter Fisher, Yoshi Uchida
Proposed speaker: Peter Fisher, Yoshi Uchida
Contact person:Peter H Fisher
(MIT),
fisherp@mit.edu
Sessions: PA-05 Tests of the Electroweak Gauge Theory / PL-06a Precision Tests of the Standard Model (Electroweak Gauge Theory (W, Z, Top, etc.)
Supporting papers: JHEP 10(1998)019
Notes:
We study the asymmetry of the decay rates between $t\rightarrow bW^+$ and $\bar t\rightarrow bW^-$ within the framework of the supersymmetric standard model. This asymmetry is induced by a new source of $CP$ violation, provided that a top squark is sufficiently light. The constraints from the electric dipole moments of the neutron and the electron are taken into account. The decay rate asymmetry could be of order 10^{-3}, which will possibly be detectable in near-future experiments.
Authors:Mayumi Aoki and Noriyuki Oshimo
Proposed speaker: Mayumi Aoki
Contact person:Mayumi Aoki
(KEK),
mayumi.aoki@kek.jp
Sessions: PA-05 Tests of the Electroweak Gauge Theory / PL-06a Precision Tests of the Standard Model (Electroweak Gauge Theory (W, Z, Top, etc.)
Supporting papers: M.Aoki and N. Oshimo, Nucl. Phys. B531 (1998) 49.
Notes:
NuTeV is a neutrino-nucleon deep inelastic scattering experiment which took its data during the 1996-1997 Fermilab fixed target run. NuTeV utilized a sign selected neutrino beam facility to minimize large systematic uncertainties identified in previous weak mixing angle measurements. This new facility allowed the use of Paschos-Wolfenstein technique in measuring weak mixing angle. The resulting uncertainty of the mass of the W boson, deduced from the weak mixing angle measurement, is comparable to those from collider measurements. The experiment also performs other electroweak measurements, using the same data. In this paper, we present precision measurement of the weak mixing angle and its interpretation as well as other electroweak measurements from the NuTeV experiment.
Authors:Jaehoon Yu for NuTeV Collaboration
Proposed speaker: Jaehoon Yu
Contact person:Jaehoon Yu
(Fermi National Accelerator Laboratory),
yu@fnal.gov
Sessions: PA-05 Tests of the Electroweak Gauge Theory / PL-06a Precision Tests of the Standard Model (Electroweak Gauge Theory (W, Z, Top, etc.)
Supporting papers:
Notes:
We present the new Coherent Exclusive Exponentiation (CEEX) for the process $e^+e^-\rightarrow f\bar f+n\gamma$, ~$f=\mu,\tau,u,d,s,c,b with validity for centre of mass energies from $\tau$ lepton threshold to 1 TeV. Coherent exponentiation, which we realize by Monte Carlo methods, is based on the YFS exponentiation but extends the latter theory to treat also the infrared real emission singularities at the level of the amplitude to all orders in $\alpha$, resulting in a more efficient resummation of the higher orders. ISR and FSR (IFI) are (is) calculated exactly in QED up to the second (first) order, including all inteference effects. EW corrections are included in first-order. Beams can be polarized arbitrarily, and all spin correlations are exact. For the total cross section and the charge asymmetry we find the total precisions of 0.2\% and 0.1\% respectively for LEP2 energies with an energy cut of 0<v_{max}<0.9 for the $\mu$ pair final state, for example.
Authors:S. Jadach, B.F.L. Ward and Z. Was
Proposed speaker: B.F.L. Ward
Contact person:Bennie Ward F.L. Ward
(University of Tennessee),
bflw@slac.stanford.edu
Sessions: PA-05 Tests of the Electroweak Gauge Theory / PL-06a Precision Tests of the Standard Model (Electroweak Gauge Theory (W, Z, Top, etc.)
Supporting papers: 1.S. Jadach, B.F.L. Ward and Z. Was, Phys. Lett.B449(1999)97-108. 2.S. Jadach, B.F.L. Ward and Z. Was, CERN-TH/99-235, in press at Comp.Phys.Commun., 2000. 3.S. Jadach, B.F.L. Ward and Z. Was, CERN-TH/98-235, submitted to E.J.Phys. C. 4.S. Jadach, B.F.L. Ward and Z. Was, CERN-TH/2000-087, to appear.
Notes:
We present precision calculations of the processes $e^+e^-\rightarrow 4-\text{fermions}$ in which the double resonant $W^+W^-$ intermediate state occurs. Referring to production of this latter intermediate state as the 'signal process', we show that, by using the Monte Carlo event generator YFSWW3-1.14, which features exact ${\cal O}(\alpha)_{prod}$ YFS exponentiation and ${\cal O}(\alpha^2)$ LL FSR, we achieve, gauge invariantly, a physical precision on the signal process total cross section $< 0.5\%$. Sample Monte Carlo data are explicitly illustrated in comparison to similar calculations by Denner {\it et al.} with the MC RacoonWW, as effected during the recent LEP2 MC Workshop. In this way, we show that a total (physical$\oplus$technical) precision tag for the signal process cross section of $< 0.5\%$ is indeed valid for LEP2 energies. Results are also given for 500 GeV with an eye toward the LC.
Authors:S. Jadach, W. P\l{}aczek, M. Skrzypek, B.F.L. Ward and Z. W\c{a}s
Proposed speaker: B.F.L. Ward
Contact person:Bennie F.L. Ward
(University of Tennessee),
bflw@slac.stanford.edu
Sessions: PA-05 Tests of the Electroweak Gauge Theory / PL-06a Precision Tests of the Standard Model (Electroweak Gauge Theory (W, Z, Top, etc.)
Supporting papers: 1.S. Jadach, W. P\l{}aczek, M. Skrzypek, B.F.L. Ward and Z. W\c{a}s, Phys.Lett.B417(1998)326. 2.S. Jadach, W. P\l{}aczek, M. Skrzypek, B.F.L. Ward and Z. W\c{a}s, CERN-TH-99-222, in press at Phys.Rev.D, 2000. 3.S. Jadach, W. P\l{}aczek, M. Skrzypek, B.F.L. Ward and Z. W\c{a}s, Precision Predictions for (Un)Stable $W^+W^-$ Pair Production At and Beyond LEP2 Energies, UTHEP-00-0101, to appear.
Notes:
Authors:I. Ots, H. Liivat, R.-K. Loide, and R. Saar
Proposed speaker: I. Ots Abstract: We use the formalism of the relativistic spin 1 density matrix obtained by boosting the nonrelativistic one to calculate analytically the spin orientation of the Z boson in the processes e^+e^- -> ZH,Z\gamma with arbitrarily polarized initial beams and the energy-angular distributions of the final leptons from the subsequent Z -> l^+l^- decay. Due to the generality of the method (arbitrarily polarized beams, unspecified spin quantization axes), the founded expressions contain in general manner all possible orientation terms.
Contact person:Ilmar - Ots
(Institute of Physics, University of Tartu Street: Riia 142),
ots@fi.tartu.ee
Sessions: PA-05 Tests of the Electroweak Gauge Theory /
Supporting papers:
Notes:- (029)
A number of topics in electroweak physics have been recently studied by the ATLAS Collaboration in the context of work for the ``Detector and Physics Performance'' Technical Design Report and the LHCC Standard Model Workshop. The LHC should measure the top mass to better than 2~GeV and the W mass to $\sim$15~MeV. Calorimetric coverage down to $|\eta| = 4.9$ should allow competitive measurements of $\Delta \sin^2 \theta_{eff}^{lept} \sim 0.0001$ per lepton channel, by using forward-backward asymmetries in $Z \rightarrow ll$ decays. Triple gauge couplings of the vector bosons, namely those associated with the $WW\gamma$ and $WWZ$ vertices, should be measured with precision between the percent and the permill after only one year of operation. Tests of dynamical symmetry breaking will come from studies of vector boson scattering at high energies. If the Higgs boson is not found, ATLAS will be placed to search for alternative symmetry breaking mechanisms, such as those provided by Technicolour.
Authors:ATLAS Collaboration
Proposed speaker:
Contact person:Fabiola Gianotti
(CERN),
fabiola.gianotti@cern.ch
Sessions: PA-05 Tests of the Electroweak Gauge Theory / PL-06a Precision Tests of the Standard Model (Electroweak Gauge Theory (W, Z, Top, etc.)
Supporting papers:
Notes:
A number of topics in electroweak physics have been recently studied by the ATLAS Collaboration in the context of work for the ``Detector and Physics Performance'' Technical Design Report and the LHCC Standard Model Workshop. The LHC should measure the top mass to better than 2~GeV and the W mass to $\sim$15~MeV. Calorimetric coverage down to $|\eta| = 4.9$ should allow competitive measurements of $\Delta \sin^2 \theta_{eff}^{lept} \sim 0.0001$ per lepton channel, by using forward-backward asymmetries in $Z \rightarrow ll$ decays. Triple gauge couplings of the vector bosons, namely those associated with the $WW\gamma$ and $WWZ$ vertices, should be measured with precision between the percent and the permill after only one year of operation. Tests of dynamical symmetry breaking will come from studies of vector boson scattering at high energies. If the Higgs boson is not found, ATLAS will be placed to search for alternative symmetry breaking mechanisms, such as those provided by Technicolour.
Authors:ATLAS Collaboration
Proposed speaker:
Contact person:Fabiola Gianotti
(CERN),
fabiola.gianotti@cern.ch
Sessions: PA-05 Tests of the Electroweak Gauge Theory / PL-06a Precision Tests of the Standard Model (Electroweak Gauge Theory (W, Z, Top, etc.)
Supporting papers:
Notes:
The LHC can be considered as a top-factory, with about 10 million t-tbar events produced in one year of running at low luminosity. This large data set will alllow very precise measurements of the properties of the top quark, which may also reveal New Physics. The mass of the top quark will be measured with a precision of better than 2 GeV. The top quark Yukawa coupling can be determined with a precision of better than 10% for a Higgs mass of about 100 GeV. T-tbar spin correlations can be observed and used to study anomalous couplings or CP violation. Heavy resonances decaying to t-tbar pairs could be detected with masses up to 3 TeV. Rare decays of the top quark can be probed for branching ratios as small as $10^-5$. Finally, the detailed study of three different mechanisms of electroweak single top production will yield a wealth of information, including precision measurements of $V_{tb}$ and of the W and top polarisations, and searches for anomalous couplings.
Authors:ATLAS Collaboration
Proposed speaker:
Contact person:Fabiola Gianotti
(CERN),
fabiola.gianotti@cern.ch
Sessions: PA-05 Tests of the Electroweak Gauge Theory / PL-06a Precision Tests of the Standard Model (Electroweak Gauge Theory (W, Z, Top, etc.)
Supporting papers:
Notes:
End of abstracts for PA-05 Tests of the Electroweak Gauge Theory