LHCb: Xmas 2010 Tara Shears, On behalf of the LHCb group.
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LHCb: Xmas 2010
Tara Shears,On behalf of the LHCb group
1. Introduction2. Electroweak physics3. Other work4. Conclusions
Xmas09 and 2010LHCb overviewLHCb kinematic planeMotivation of ewk measurements
Introduction
Electroweak: Z, W, ratios
Other work: other Z channels, exclusive dimuons, AFB
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 2010First paper on W, Z productionWork towards paper on low mass DY productionWork towards another on exclusive states.Plus continue rest of group programme.
1. Introduction2. Status of studies3. Reach with 100 pb-1
4. 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 trackingThemis, David, Kurt, Karol, Abdi, James, Emma, Henry
ElectroweakTara, Themis, Kurt, Karol, Stephanie, Emma, Myfanwy, Henry
B physicsThemis, David, James
Why?
W/Z provide high p track samples:Tracking performance, track stability, errors, ipExtends ewk: W, tau etc.
Optimal tracking needed for B physics
Ewk / B can be extended in NP searches in future.Long lived massive particlesBoson + heavy flavour
BsDsDs
+ tracking work to optimise lifetime distribution
Plots courtesy of James
High pT tracking studiesErrors, ghosts, preselection, efficiency
Muon studiesTrigger, identification, backgrounds
Electron studiesTrigger, identification, backgrounds
Theory studiesProduction studies:
Z, W, Z, ZeeZ + jet*, *eepppp+ (luminosity), excl. J/, '
PDF sensitivity studies Underlying event studiesAFB
*(Liverpool contributions)
Electroweak working group+ MSTW/NNPDF collaboration (PDFs)+ Stirling/Harland-Lang/Khoze (exclusives)+ LHC ewk WG (Mangano et al)
1. Introduction2. Cross-sections3. Other work4. Conclusions
OverviewLHCb kinematic regionPredictions of W, Z productionMeasurement definitions
Beam Beam
MuonCalo
Interaction point
Tracking
Vertex detector
300mrad
Fully instrumented within 1.9 ≤ ≤ 4.9Trigger: p > 3 GeV, pt > 0.5 GeV, m > 2.5 GeV
1. Introduction2. Cross-sections3. Other work4. Conclusions
OverviewW, Z productionMeasurement definitions
2010: 37.7 pb-1 data recorded16.5 ± 1.7 pb-1 used
2011: hope for 1-2 fb-1 of data
1. Introduction2. Cross-sections3. Other work4. Conclusions
OverviewW, Z productionMeasurement definitions
8% of Z within LHCb acceptance
17% (16%) of W+ (W-) within LHCb acceptance
1. Introduction2. Cross-sections3. Other work4. Conclusions
Overview
W, Z productionMeasurement definitions
1. Introduction2. Cross-sections3. Other work4. Conclusions
Overview
W, Z productionMeasurement definitions
X, Q2 explored by previous experimental data
1. Introduction2. Cross-sections3. Other work4. Conclusions
Overview
W, Z productionMeasurement definitions
X, Q2 explored byLHCb.Z, W: x of 10-4, 10-1
(low mass * 10-6)
1. Introduction2. Cross-sections3. Other work4. Conclusions
Overview
W, Z productionMeasurement definitions
Cross-sections known to NNLOPDF uncertainty dominatesKnown to ~1% at y ~1.5-2, 6-8% at y~5
1. Introduction2. Cross-sections3. Other work4. Conclusions
Overview
W, Z productionMeasurement definitions
Cancel or highlight PDF uncertainties with ratiosR+ tests dV/uV ratioAW tests difference between uV and dV
RWZ almost insensitive to PDFs
LHCb
1. Introduction2. Cross-sections3. Other work4. Conclusions
Overview
W, Z productionMeasurement definitions
€
σ(Z→ μμ : 2 <η μ < 4.5,PTμ > 20GeV ,81< Mμμ <101GeV )
€
σ(W → μν : 2 <η μ < 4.5,PTμ > 20GeV )
1. Introduction2. Cross-sections3. Other work4. Conclusions
OverviewW, Z production
Measurement definitions
Definition of measured cross-sections:
(as function of Z rapidity)
(as function of muon pseudorapidity)
€
σ Z→μμ (Δy) =N tot
Z −NbkgZ
εZL
Z selection
Z background estimation
1. Introduction
2. Cross-sections3. Other work4. Conclusions
NZ, Nbkg
NW, Nbkg
EfficienciesResults
Trigger:Single , pT > 10 GeV
Muon:Good track quality (σp/p, 2 probability) pT> 20 GeV 2.0 < < 4.5
Z: 81 < m() < 101 GeV
Z =1.00 (by definition to compare with theory)
1. Introduction
2. Cross-sections3. Other work4. Conclusions
NZ, Nbkg
NW, Nbkg
EfficienciesResults
NZ = 833
Backgrounds:Z ( ~ 0.2 )Heavy flavour ( ~ 1)K/ ( < 0.03)Nbkg = 1.2 ± 1.2
LHCb preliminary
Data, simulation
1. Introduction
2. Cross-sections3. Other work4. Conclusions
NZ, Nbkg
NW, Nbkg
EfficienciesResults
W selection
W background estimation€
σW→μν (Δη ) =N tot
W −NbkgW
εWL
1. Introduction
2. Cross-sections3. Other work4. Conclusions
NZ, Nbkg
NW, Nbkg
EfficienciesResults
Trigger:Single , pT > 10 GeV
Muon: Good track quality (σp/p, 2 probability)pT > 20 GeV 2.0 < < 4.5Impact parameter significance < 2pT in R=(2+2)=0.5 cone around
< 2 GeV
Rest of event: Mass < 20 GeVpT < 10 GeV
W= 55.0 1.0%
(data driven, using Z events)
1. Introduction
2. Cross-sections3. Other work4. Conclusions
NZ, Nbkg
NW, Nbkg
EfficienciesResults
LHCb preliminary
1. Introduction
2. Cross-sections3. Other work4. Conclusions
NZ, Nbkg
NW, Nbkg
EfficienciesResults
NW+ = 7624 NW - = 5732
Background sources:Z (1 in acceptance)Z W Hadronic events
Data SimulationData + simulation
Fit muon pT spectrum in data to expected shapesfor signal and background,extract Nbkg+, Nbkg-
1. Introduction
2. Cross-sections3. Other work4. Conclusions
NZ, Nbkg
NW, Nbkg
EfficienciesResults
Nbkg+ = 2194 ± 150
Nbkg- = 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-sections3. Other work4. Conclusions
NZ, Nbkg
NW, Nbkg
EfficienciesResults
Measurements made in kinematic acceptance
AZ, AW = 1
€
Z = AZεZtrigεZ
trackεZmuonεZ
selection
€
W = AWεWtrigεW
trackεWmuonεW
selection
1. Introduction
2. Cross-sections3. Other work4. Conclusions
NZ, Nbkg
NW, Nbkg
EfficienciesResults
Determine from data (Z sample)
Tag: 1 identified muon having fired single muon trigger
Probe: 1 identified muon
€
Z = AZεZtrigεZ
trackεZmuonεZ
selection
€
W = AWεWtrigεW
trackεWmuonεW
selection
1. Introduction
2. Cross-sections3. Other work4. Conclusions
NZ, Nbkg
NW, Nbkg
EfficienciesResults
Efficiency is flat in , pT.
No evidence for charge bias
W =72 1%
Z =86 1%
LHCb preliminary - +
pT
1. Introduction
2. Cross-sections3. Other work4. Conclusions
NZ, Nbkg
NW, Nbkg
EfficienciesResults
LHCb preliminary
€
Z = AZεZtrigεZ
trackεZmuonεZ
selection
€
W = AWεWtrigεW
trackεWmuonεW
selection
Determine from data (Z sample)
Tag: 1 identified muon
Probe: 1 muon stub + TT hit
(TT not used in tracking)
1. Introduction
2. Cross-sections3. Other work4. Conclusions
NZ, Nbkg
NW, Nbkg
EfficienciesResults
Efficiency flat in , pT
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-sections3. Other work4. Conclusions
NZ, Nbkg
NW, Nbkg
EfficienciesResults
€
Z = AZεZtrigεZ
trackεZmuonεZ
selection
€
W = AWεWtrigεW
trackεWmuonεW
selection
Determine from data (Z sample)
Tag: 1 identified muon
Probe:1 identified track
1. Introduction
2. Cross-sections3. Other work4. Conclusions
NZ, Nbkg
NW, Nbkg
EfficienciesResults
Efficiency flat in , pT
No evidence of charge bias
W = 98.2 0.5%
Z = 96.5 0.7%LHCb preliminary
datasimulationtruth level
1. Introduction
2. Cross-sections3. Other work4. Conclusions
NZ, Nbkg
NW, Nbkg
EfficienciesResults
€
Z = AZεZtrigεZ
trackεZmuonεZ
selection
€
W = AWεWtrigεW
trackεWmuonεW
selection
Found before:Z: (simulation) 1.00W: (data driven, using Z events) 55.0 1.0%
1. Introduction
2. Cross-sections3. Other work4. Conclusions
NZ, Nbkg
NW, Nbkg
EfficienciesResults
LHCb preliminary MCFM NLO+MSTW08 16.5 pb-1 s=7 TeV
Z cross-section
1. Introduction
2. Cross-sections3. Other work4. Conclusions
NZ, Nbkg
NW, Nbkg
Efficiencies
Results
W cross-section, asymmetry
1. Introduction
2. Cross-sections3. Other work4. Conclusions
NZ, Nbkg
NW, Nbkg
Efficiencies
Results
LHCb preliminary
1. Introduction
2. Cross-sections3. Other work4. Conclusions
NZ, Nbkg
NW, Nbkg
Efficiencies
Results
1. Introduction2. Cross-sections
3. Other work4. Conclusions
Other Z decay channelsExclusive AFB
Other work (briefly):
Other Z decay channels
Exclusive
AFB
… and other channelse.g. Zee
1. Introduction2. Cross-sections
3. Other work4. Conclusions
Other Z decay channelsExclusive AFB
… and other channelse.g. Z
1. Introduction2. Cross-sections
3. Other work4. Conclusions
Other Z decay channelsExclusive AFB
Exclusive production
Two muons: dca<0.15 mm; M>1 GeV; PT < 0.9 GeV; SPD multiplicity<5; 0 extra tracks.
Exclusive = no charged+neutral activity 1.9<<4.9No charged tracks -4<<-2
1. Introduction2. Cross-sections
3. Other work4. Conclusions
Other Z decay channels
Exclusive AFB
1. Introduction2. Cross-sections
3. Other work4. Conclusions
Other Z decay channels
Exclusive AFB
€
AFB0, f =
3
4A f uAu + dAd + sAs( )
€
A f =2gVf gAfgVf2 + gAf
2
AFB sensitive to sin2W
Uncertainties from :Forward (quark) directionPDF knowledge of sea
LHCb: predominately valence - sea collisionsss contribution reduced
Pythia: generator study
LHCb
94% correct
1. Introduction2. Cross-sections
3. Other work4. Conclusions
Other Z decay channelsExclusive AFB
Statistical errors only:
1 fb-1 implies 4% statistical precision on AFB
implies 0.15% statistical precision on sin2W (cf. 0.07% world average)
Studies ongoing: PDF uncertainties (estimated at 0.04%)Needs theoretical prediction of comparable precision
1. Introduction2. Cross-sections
3. Other work4. Conclusions
Other Z decay channelsExclusive AFB
1. Introduction2. Cross-sections3. Oher work
4. Conclusions
2010:Good year for electroweak physicsTested electroweak sector to 6% at LHCFirst signs of exclusive dimuons
2011:Papers comingMore stringent tests of the SMPDF constraintsFirst AFB measurementFirst B measurementsTracking work allows extension to taus, B and beyond.
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