Measurement of Wgamma Production in pp Collisions at √s=1.96 TeV


The analysis was performed by
Beate Heinemann (LBL)
and Ai Nagano (University of Tsukuba)
The Standard Model predictions for Wgamma production are tested using an integrated luminosity of 1 fb-1 of pp collision data collected at the Collider Detector at Fermilab. The cross sections are measured by selecting leptonic decays of the W bosons and photons with transverse energy ET > 7 GeV that are well separated from leptons. The production cross sections and kinematic distributions for the Wgamma data are compared to SM predictions.
Event criteria for W(μ)+ γ
Muon
 pT (transverse momentum) > 20GeV, | η (μ) | < 1.1
Neutrino MET (Missing Transverse Energy) > 20 GeV
Transverse mass(μ,ν)
 30 < MT < 120 GeV
Photon
 ET(Transverse Energy) > 7 GeV, |η(γ)|<1.1


W(μ)+ γ events yields
Luminosity 1 fb-1
Number of Events
signal MC 541.7 ± 4.0(stat.) ± 1.57(syst.)
W+jet background
 194.3 ± 0.15(stat.) ± 66.91(syst.)
Z+ γ background
 112.0 ± 0.39(stat.) ± 0.39(syst.)
W(τ)+ γ background
 12.4 ± 0.60(stat.) ± 0.60(syst.)
Total Expected
 860.4 ± 4.84(stat.) ± 112.96(syst.)
Data
 857




Event criteria for W(e)+ γ
Central Electron
 ET (Transverse Energy) > 25GeV, |η(e)|<1.1
Neutrino MET (Missing Transverse Energy) > 25 GeV
Transverse mass(e,ν)
 30 < MT < 120 GeV
Photon
 ET(Transverse Energy) > 7 GeV, |η(γ)|<1.1


W(e)+ &gamma events yields
Luminosity 1 fb-1
Number of Events
signal MC 663.34 ± 4.79(stat.) ± 47.73(syst.)
W+jet background
 243.33 ± 0.06(stat.) ± 90.20(syst.)
Z+ &gamma background
 25.53 ± 0.24(stat.) ± 1.84(syst.)
W(&tau)+ &gamma background
 12.88 ± 0.65(stat.) ± 0.93(syst.)
Total Expected
 945.08 ± 4.09(stat.) ± 66.95(syst.)
Data
 908




Cross section for ET(&gamma)>7 GeV and &Delta R(lepton,&gamma)>0.7:

&sigma(W&gamma) x BR(W-> &mu &nu) [pb]
 19.11 ± 1.04(stat.) ± 2.40(sys.) ± 1.11(lumi.)
&sigma(W&gamma) x BR(W-> e &nu) [pb]
 17.21 ± 0.83(stat.) ± 2.24(sys.) ± 1.00(lumi.)
&sigma(W&gamma) x BR(W-> lepton &nu) [pb]
 18.03 ± 0.65(stat.) ± 2.55(sys.) ± 1.05(lumi.)
Theory : σ(W γ) x BR(W-> lepton + ν) [pb] 19.3±1.4

Kinematic Distributions W+gamma in Muon Channel
W+gamma in Electron Channel
W+gamma in e+μ Channel
pT(gamma) photon p<sub>T</sub>
gif | eps
 photon p<sub>T</sub>
gif | eps
 photon p<sub>T</sub>
gif | eps
Wgamma: DeltaR(lepton,gamma) ΔR(μ,γ)
gif | eps
 ΔR(e,γ)
gif | eps
 ΔR(lepton,γ)
gif | eps
Wgamma: MT(lepton,ν) MT(&mu,nu)
gif | eps
 MT(e,nu)
gif | eps
 MT(lepton,nu)
gif | eps
Wgamma: cluster transverse mass (lepton, photon, neutrino)
MT(lgamma, nu)
gif | eps
 MT(lgamma, nu)
gif | eps
 MT(lgamma, nu)
gif | eps
Wgamma: Cluster Transverse Mass versus MT
cluster mass vs mt
gif | eps
 cluster mass vs mt
gif | eps
 cluster mass vs mt
gif | eps


June 29, 2007