LHCb: Xmas 2010 Tara Shears, On behalf of the LHCb group

1. Introduction 2. Electroweak physics 3. Other work 4. Conclusions Xmas09 and 2010 LHCb overview LHCb kinematic plane Motivation of ewk measurements Introduction Electroweak: Z, W, ratios Other work: other Z channels, exclusive dimuons, A FB Conclusions

Data: looking forward to studying high momentum muons with LHCb. W, Z, DY selection studies estimate a statistical precision < 1% with ~100 pb -1 of data (2010). Systematic errors dominated by luminosity uncertainty. Systematic errors for low mass DY need to be studied. Exclusive J/psi have similar yield. Plan: by end 2010 First paper on W, Z production Work towards paper on low mass DY production Work towards another on exclusive states. Plus continue rest of group programme. 1. Introduction 2. Status of studies 3. Reach with 100 pb Conclusions XMAS09 - reminder

Achievements/ hardware plans: VELO operations VELO replacement build Upgrade plans (more build) Thanks to all the workshop & downstairs crew.

Physics: VELO performance and tracking Themis, David, Kurt, Karol, Abdi, James, Emma, Henry Electroweak Tara, Themis, Kurt, Karol, Stephanie, Emma, Myfanwy, Henry B physics Themis, David, James

Why? W/Z provide high p track samples: Tracking performance, track stability, errors, ip Extends ewk: W, tau etc. Optimal tracking needed for B physics Ewk / B can be extended in NP searches in future. Long lived massive particles Boson + heavy flavour

BsDsDsBsDsDs + tracking work to optimise lifetime distribution Plots courtesy of James

High p T tracking studies Errors, ghosts, preselection, efficiency Muon studies Trigger, identification, backgrounds Electron studies Trigger, identification, backgrounds Theory studies Production studies: Z , W , Z , Z  ee Z  + jet  * ,  *  ee pp  pp+  (luminosity), excl. J/ ,  ' PDF sensitivity studies Underlying event studies A FB *(Liverpool contributions) Electroweak working group + MSTW/NNPDF collaboration (PDFs) + Stirling/Harland- Lang/Khoze (exclusives) + LHC ewk WG (Mangano et al) 1. Introduction 2. Cross-sections 3. Other work 4. Conclusions Overview LHCb kinematic region Predictions of W, Z production Measurement definitions

Beam MuonCalo Interaction point Tracking Vertex detector 300mrad Fully instrumented within 1.9 ≤  ≤ 4.9 Trigger: p  > 3 GeV, pt  > 0.5 GeV, m  > 2.5 GeV 1. Introduction 2. Cross-sections 3. Other work 4. Conclusions Overview W, Z production Measurement definitions

2010: 37.7 pb -1 data recorded 16.5 ± 1.7 pb -1 used 2011: hope for 1-2 fb -1 of data 1. Introduction 2. Cross-sections 3. Other work 4. Conclusions Overview W, Z production Measurement definitions

8% of Z within LHCb acceptance 17% (16%) of W + (W - ) within LHCb acceptance 1. Introduction 2. Cross-sections 3. Other work 4. Conclusions Overview W, Z production Measurement definitions

  1. Introduction 2. Cross-sections 3. Other work 4. Conclusions Overview W, Z production Measurement definitions

X, Q 2 explored by previous experimental data 1. Introduction 2. Cross-sections 3. Other work 4. Conclusions Overview W, Z production Measurement definitions

X, Q 2 explored by LHCb. Z, W: x of 10 -4, (low mass  *  ) 1. Introduction 2. Cross-sections 3. Other work 4. Conclusions Overview W, Z production Measurement definitions

Cross-sections known to NNLO PDF uncertainty dominates Known to ~1% at y ~1.5-2, 6-8% at y~5 1. Introduction 2. Cross-sections 3. Other work 4. Conclusions Overview W, Z production Measurement definitions

Cancel or highlight PDF uncertainties with ratios R + tests d V /u V ratio A W tests difference between u V and d V R WZ almost insensitive to PDFs LHCb 1. Introduction 2. Cross-sections 3. Other work 4. Conclusions Overview W, Z production Measurement definitions

1. Introduction 2. Cross-sections 3. Other work 4. Conclusions Overview W, Z production Measurement definitions Definition of measured cross-sections: (as function of Z rapidity) (as function of muon pseudorapidity)

Z selection Z background estimation 1. Introduction 2. Cross-sections 3. Other work 4. Conclusions N Z, N bkg N W, N bkg Efficiencies Results

Trigger: Single , p T > 10 GeV Muon: Good track quality (  p /p,  2 probability) p T > 20 GeV 2.0 <  < 4.5 Z: 81 < m(  ) < 101 GeV  Z =1.00 (by definition to compare with theory) 1. Introduction 2. Cross-sections 3. Other work 4. Conclusions N Z, N bkg N W, N bkg Efficiencies Results

N Z = 833 Backgrounds: Z  ( ~ 0.2 ) Heavy flavour ( ~ 1) K/  ( < 0.03) N bkg = 1.2 ± 1.2 LHCb preliminary Data, simulation 1. Introduction 2. Cross-sections 3. Other work 4. Conclusions N Z, N bkg N W, N bkg Efficiencies Results

W selection W background estimation 1. Introduction 2. Cross-sections 3. Other work 4. Conclusions N Z, N bkg N W, N bkg Efficiencies Results

Trigger: Single , p T > 10 GeV Muon: Good track quality (  p /p,  2 probability) p T > 20 GeV 2.0 <  < 4.5 Impact parameter significance < 2  p T in R=  (  2 +  2 )=0.5 cone around  < 2 GeV Rest of event: Mass < 20 GeV  p T < 10 GeV  W = 55.0  1.0% (data driven, using Z events) 1. Introduction 2. Cross-sections 3. Other work 4. Conclusions N Z, N bkg N W, N bkg Efficiencies Results

LHCb preliminary 1. Introduction 2. Cross-sections 3. Other work 4. Conclusions N Z, N bkg N W, N bkg Efficiencies Results

N W+ = 7624 N W - = 5732 Background sources: Z   (1  in acceptance) Z   W   Hadronic events Data Simulation Data + simulation Fit muon p T spectrum in data to expected shapes for signal and background, extract N bkg+, N bkg- 1. Introduction 2. Cross-sections 3. Other work 4. Conclusions N Z, N bkg N W, N bkg Efficiencies Results

N bkg+ = 2194 ± 150 N bkg- = 1654 ± 150 Z (fixed with sim)  (fixed and scaled to W) QCD: fit fraction. (shape from data) W+/-: fit fraction (shape from MC) LHCb preliminary ++ -- Perform fit in  bins for differential results 1. Introduction 2. Cross-sections 3. Other work 4. Conclusions N Z, N bkg N W, N bkg Efficiencies Results

Measurements made in kinematic acceptance A Z, A W = 1 1. Introduction 2. Cross-sections 3. Other work 4. Conclusions N Z, N bkg N W, N bkg Efficiencies Results

Determine from data (Z sample) Tag: 1 identified muon having fired single muon trigger Probe: 1 identified muon 1. Introduction 2. Cross-sections 3. Other work 4. Conclusions N Z, N bkg N W, N bkg Efficiencies Results

Efficiency is flat in , p T. No evidence for charge bias  W =72  1%  Z =86  1% LHCb preliminary -- ++   pTpT  1. Introduction 2. Cross-sections 3. Other work 4. Conclusions N Z, N bkg N W, N bkg Efficiencies Results

LHCb preliminary Determine from data (Z sample) Tag: 1 identified muon Probe: 1 muon stub + TT hit (TT not used in tracking) 1. Introduction 2. Cross-sections 3. Other work 4. Conclusions N Z, N bkg N W, N bkg Efficiencies Results

Efficiency flat in , p T Two regions considered in   W+ = 73  3%  W - = 78  3%  Z = 83  3% LHCb preliminary (+, - different average efficiency due to different  distribution)  1. Introduction 2. Cross-sections 3. Other work 4. Conclusions N Z, N bkg N W, N bkg Efficiencies Results

Determine from data (Z sample) Tag: 1 identified muon Probe:1 identified track 1. Introduction 2. Cross-sections 3. Other work 4. Conclusions N Z, N bkg N W, N bkg Efficiencies Results

Efficiency flat in , p T No evidence of charge bias  W = 98.2  0.5%  Z = 96.5  0.7% LHCb preliminary   data simulation truth level 1. Introduction 2. Cross-sections 3. Other work 4. Conclusions N Z, N bkg N W, N bkg Efficiencies Results

Found before: Z: (simulation) 1.00 W: (data driven, using Z events) 55.0  1.0% 1. Introduction 2. Cross-sections 3. Other work 4. Conclusions N Z, N bkg N W, N bkg Efficiencies Results

LHCb preliminary MCFM NLO+MSTW pb -1  s=7 TeV Z cross-section 1. Introduction 2. Cross-sections 3. Other work 4. Conclusions N Z, N bkg N W, N bkg Efficiencies Results

W cross-section, asymmetry 1. Introduction 2. Cross-sections 3. Other work 4. Conclusions N Z, N bkg N W, N bkg Efficiencies Results

LHCb preliminary 1. Introduction 2. Cross-sections 3. Other work 4. Conclusions N Z, N bkg N W, N bkg Efficiencies Results

1. Introduction 2. Cross-sections 3. Other work 4. Conclusions Other Z decay channels Exclusive  A FB Other work (briefly): Other Z decay channels Exclusive  A FB

… and other channels e.g. Z  ee 1. Introduction 2. Cross-sections 3. Other work 4. Conclusions Other Z decay channels Exclusive  A FB

… and other channels e.g. Z  1. Introduction 2. Cross-sections 3. Other work 4. Conclusions Other Z decay channels Exclusive  A FB

Exclusive  production Two muons: dca<0.15 mm; M  >1 GeV; P T  < 0.9 GeV; SPD multiplicity<5; 0 extra tracks. Exclusive = no charged+neutral activity 1.9<  <4.9 No charged tracks -4<  <-2 1. Introduction 2. Cross-sections 3. Other work 4. Conclusions Other Z decay channels Exclusive  A FB

1. Introduction 2. Cross-sections 3. Other work 4. Conclusions Other Z decay channels Exclusive  A FB

A FB sensitive to sin 2  W Uncertainties from : Forward (quark) direction PDF knowledge of sea LHCb: predominately valence - sea collisions ss contribution reduced Pythia: generator study LHCb 94% correct 1. Introduction 2. Cross-sections 3. Other work 4. Conclusions Other Z decay channels Exclusive  A FB

Statistical errors only: 1 fb -1 implies 4% statistical precision on A FB implies 0.15% statistical precision on sin 2  W (cf. 0.07% world average) Studies ongoing: PDF uncertainties (estimated at 0.04%) Needs theoretical prediction of comparable precision 1. Introduction 2. Cross-sections 3. Other work 4. Conclusions Other Z decay channels Exclusive  A FB

1. Introduction 2. Cross-sections 3. Oher work 4. Conclusions 2010: Good year for electroweak physics Tested electroweak sector to 6% at LHC First signs of exclusive dimuons 2011: Papers coming More stringent tests of the SM PDF constraints First A FB measurement First B measurements Tracking work allows extension to taus, B and beyond.