C. K. MackayEPS 2003 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. MackayEPS 2003 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. MackayEPS 2003 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. MackayEPS 2003 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. MackayEPS 2003 Precision of the W Mass 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  M t ~ 2 GeV at the LHC, we require  M W ~ 15 MeV W Transverse Mass Distribution including expected detector resolution Measurement of the W mass is performed in the leptonic channels using the transverse mass:

C. K. MackayEPS 2003 Precision of the W Mass Cuts: Isolated charged lepton p T > 25 GeV |  | < 2.4 Missing transverse energy E T Miss > 25 GeV No jets with p T > 30 GeV Recoil < 20GeV Sources of Uncertainty: Statistical uncertainty pp  W + X  = 30 nb (l= e,  ) W  l l 3 x 10 8 events < 2MeV for 10 fb-1 Systematic Error Detector performance Physics Source  M W (MeV) Statistics  2 2 E-p scale15 Energy resolution5 Recoil model5 Lepton identification5 pTWpTW 5 Parton distribution functions  10 W width7 Radiative decays10 Background5 Total  25  Reduces the error on log M H from 0.2 to year, 1 lepton species:  25 MeV Combining lepton channels:  20 MeV Combining experiments:  15 MeV

C. K. MackayEPS 2003 Top Mass Together with M W 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 tt leptonic decays (t  bW) Single lepton W  l, W  jj 29.6 % 2.5 x 10 6 events Di-lepton W  l, W  l 4.9 % 400,000 events - -

C. K. MackayEPS 2003 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. MackayEPS 2003 Single Top Quark Production Probe the t-W-b vertex Direct measurement of the CKM matrix element V tb  (t)  |V tb | 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)D0CDFLHC  Wg <22<13245  Wt --60  W* <17<1810 For each process:   |V tb | 2 Systematic errors: B-jet tagging, luminosity, theoretical (dominates V tb measurements) ProcessS/BS/√B  V tb /V tb Statistical  V tb /V tb Theory W-g %7.5% Wt %9.5% W* %3.8%

C. K. MackayEPS 2003 WW  Vertex 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 (Q W ) 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: p T  distribution Radiation zero  ( ,l) M T distribution Angular distribution  W Shaded = SM Clear =  = 0.01

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

C. K. MackayEPS 2003 ZZ  & Z  Vertices Anomalous couplings are h V i (i = 1-4, V = Z,  ) h V 3 and h V 4 are the CP-conserving couplings and h V 1 and h V 2 are the CP-violating couplings relating to the transition moments of the Z Observing the anomalies: p T  distribution M T distribution

C. K. MackayEPS 2003 ZZ  & Z  Vertices Main Backgrounds Z + Jet Z  Cuts |  ,l | < 2.4 p T  > 100 GeV p Tl > 25 GeV  R( ,l) > 0.7 M T (ll  ) > 100 GeV Predicted Limits  = 1 TeV  = 3 TeV Typically order of magnitude improvement hZ3hZ3 hZ4hZ4 10 fb -1 ± 2.0 x ± 8.2 x fb -1 ± 7.8 x ± 3.6 x hZ3hZ3 hZ4hZ4 10 fb -1 ± 2.3 x ± 1.9 x fb -1 ± 1.5 x ± 8.5 x 10 -6

C. K. MackayEPS 2003 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  M W and  M t improve error on log M H ~ 50%. Triple Gauge Couplings: WW  : Anomalies clearly observed in p T(  ) distribution ZZ  : Anomalies clearly observed in p T(  ) and M T(ll  ) distribution Predicted Limits: ~ order of magnitude improvement