Measurement of Wγ and Zγ production in pp collisions at √s = 7 TeV

Abstract

A measurement of Wγ and Zγ production in proton-proton collisions at√s=7 TeV is presented. Results are based on a data sample recorded by the CMS experiment at the LHC, corresponding to an integrated luminosity of 36 pb^-1. The electron and muon decay channels of the W and Z are used. The total cross sections are measured for photon transverse energy E^γ _T>10 GeV and spatial separation from charged leptons in the plane of pseudorapidity and azimuthal angle ΔR(ℓ,γ)>0.7, and with an additional dilepton invariant mass requirement of Mℓℓ>50 GeV for the Zγ process. The following cross section times branching fraction values are found: σ(pp→W_γ+X)xB(W→lν)=56.3±5.0(stat.)±5.0(syst.)±2.3(lumi.) pb and σ(pp→Z_γ+X)xB(Z→ll)=9.4±1.0(stat.)±0.6(syst.)±0.4(lumi.) pb. These measurements are in agreement with standard model predictions. The first limits on anomalous WWγ, ZZγ, and Z_γγ trilinear gauge couplings at √s=7 TeV are set.