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Electroweak Physics and the Top Quark Mass at the LHC

Electroweak Physics and the Top Quark Mass at the LHC. Kate Mackay University of Bristol On behalf of the Atlas & CMS Collaborations EPS Aachen, July 2003. Outline. The Atlas and CMS Detectors W Mass Measurement of the W mass Errors on W mass measurement Top Physics

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Electroweak Physics and the Top Quark Mass at the LHC

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  1. Electroweak Physics and the Top Quark Mass at the LHC Kate Mackay University of Bristol On behalf of the Atlas & CMS Collaborations EPS Aachen, July 2003 C. K. Mackay EPS 2003

  2. Outline • The Atlas and CMS Detectors • W Mass • Measurement of the W mass • Errors on W mass measurement • Top Physics • Top Quark Mass measurements • Errors on top mass measurement • Single top quark production • Triple Gauge Boson Couplings • WW • ZZ and Z • Summary C. K. Mackay EPS 2003

  3. The Atlas Detector Inner Detector: Silicon pixels and strips Transition radiation tracker EM Calorimeter: Sampling Pb/LAr Hadron Calorimeters: Barrel: Fe/Scintillating tiles Endcaps: Cu & W /LAr Muon Spectrometer: Drift tubes & Cathode strip Tubes, resistive plate chambers Magnet: 2T Solenoid C. K. Mackay EPS 2003

  4. The CMS Detector Inner Detector: Silicon pixels and strips Preshower: Lead and silicon strips EM Calorimeter: Lead Tungstate Hadron Calorimeters: Barrel & Endcap: Cu/Scintillating sheets Forward: Steel and Quartz fibre Muon Spectrometer: Drift tubes, cathode strip chambers and resistive plate chambers Magnet: 4T Solenoid C. K. Mackay EPS 2003

  5. The W mass is known with a precision of ± 34 MeV from LEP2 and the Tevatron - What is the motivation for improving at the LHC? Higgs mass estimation Radiative corrections For equal weights in a 2 test: If Mt ~ 2 GeV at the LHC, we require MW ~ 15 MeV W Transverse Mass Distribution including expected detector resolution Precision of the W Mass Measurement of the W mass is performed in the leptonic channels using the transverse mass: C. K. Mackay EPS 2003

  6. Precision of the W Mass Cuts: Isolated charged lepton pT > 25 GeV || < 2.4 Missing transverse energy ETMiss > 25 GeV No jets with pT > 30 GeV Recoil < 20GeV Sources of Uncertainty: • Statistical uncertainty pp  W + X  = 30 nb (l= e,) W  ll 3 x 108 events < 2MeV for 10 fb-1 • Systematic Error Detector performance Physics  Reduces the error on log MH from 0.2 to 0.1 1 year, 1 lepton species:  25 MeV Combining lepton channels:  20 MeV Combining experiments:  15 MeV C. K. Mackay EPS 2003

  7. Together with MW helps to constrain the SM Higgs mass tt production: main background to new physics processes: production and decay of Higgs bosons and SUSY particles Top events used to calibrate the calorimeter jet scale Precision measurements in the top sector provide information of the fermion mass hierarchy At low luminosity: Semi-leptonic: best channel for top mass measurement (pure hadronic channel can also be used) Error dominated by systematic errors: Jet energy scale Final state gluon radiation Top Mass - - C. K. Mackay EPS 2003

  8. Top Mass Measurements Predicted error on the top mass measurement from the semi-leptonic channel of 1.3 GeV (Di-leptonic channel:  2 GeV) C. K. Mackay EPS 2003

  9. Probe the t-W-b vertex Direct measurement of the CKM matrix element Vtb (t)  |Vtb| New Physics – heavy Vector Boson W’ Source of high polarized tops Background: tt-, Wbb-, Wjj Tevatron: (t) ~ (t-) LHC: (t) ~ 1.5 (t-)  LHC provides a new scenario for single top quark production.  (pb) D0 CDF LHC Wg <22 <13 245 Wt - - 60 W* <17 <18 10 For each process:   |Vtb|2 Systematic errors: B-jet tagging, luminosity, theoretical (dominates Vtb measurements) Single Top Quark Production C. K. Mackay EPS 2003

  10. Parameters  and  are related to physical properties of the W boson. They are CP-conserving couplings and relate to the electric quadrupole moment of the W (QW) and its magnetic dipole moment (W) In the SM  =1 (  = 0) and  =0 at tree level. Anomalous contribution is enhanced at high √s Observing the anomalies: pT  distribution Radiation zero (,l) MT distribution Angular distribution W WW Vertex Shaded = SM Clear =  = 0.01 C. K. Mackay EPS 2003

  11. pT Cuts: () > 100 GeV, (l) > 25 GeV, pT miss > 50 GeV Jet veto R(,l) > 0.7 MT (l ,pT miss) > 90 GeV LHC Limits for 10 fb-1 and 100 fb-1 Limits on W C. K. Mackay EPS 2003

  12. Anomalous couplings are hVi (i = 1-4, V = Z, ) hV3 and hV4 are the CP-conserving couplings and hV1 and hV2 are the CP-violating couplings relating to the transition moments of the Z Observing the anomalies: pT  distribution MT distribution ZZ & Z Vertices C. K. Mackay EPS 2003

  13. Main Backgrounds Z + Jet Z  Cuts |,l | < 2.4 pT > 100 GeV pTl > 25 GeV R(,l) > 0.7 MT (ll) > 100 GeV Predicted Limits  = 1 TeV  = 3 TeV Typically order of magnitude improvement ZZ & Z Vertices C. K. Mackay EPS 2003

  14. Summary • LHC: precision measurements, unexplored kinematic regions, high-statistics (W, Z, b, t factory) • W Mass: Measured with a precision of ~ 15 MeV (Combining lepton channels and both Atlas and CMS) • Top Mass: Measured with a precision of ~ 1.3 GeV  Higgs Mass: Together MW and Mt improve error on log MH ~ 50%. • Triple Gauge Couplings: • WW: Anomalies clearly observed in pT() distribution • ZZ: Anomalies clearly observed in pT() and MT(ll) distribution • Predicted Limits: ~ order of magnitude improvement C. K. Mackay EPS 2003

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