Measurement of W-gamma and Z-gamma production in pp collisions at sqrt(s) = 7 TeV

TL;DR

This paper reports measurements of W-gamma and Z-gamma production cross sections in proton-proton collisions at 7 TeV using CMS data, confirming Standard Model predictions and setting limits on anomalous gauge couplings.

Contribution

First measurement of W-gamma and Z-gamma production cross sections at 7 TeV with CMS, including limits on anomalous gauge couplings.

Findings

Measured cross sections are consistent with Standard Model predictions.

Set the first limits on anomalous WWγ, ZZγ, and Zγγ couplings at 7 TeV.

Results demonstrate the capability of CMS to probe electroweak processes.

Abstract

A measurement of W-gamma and Z-gamma production in proton-proton collisions at sqrt(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 inverse picobarns. The electron and muon decay channels of the W and Z are used. The total cross sections are measured for photon transverse energy >10 GeV and spatial separation from charged leptons in the plane of pseudorapidity and azimuthal angle >0.7, and with an additional dilepton invariant mass requirement of > 50 GeV for the Z-gamma process. The following cross section times branching fraction values are found: sigma(pp to W-gamma+X) B(W to lepton neutrino) = 56.3 +/- 5.0 (stat.) +/- 5.0 (syst.) +/- 2.3 (lumi.) pb and sigma(pp to Z-gamma+X) B}(Z to lepton lepton) = 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 WW gamma, ZZ gamma, and Z gamma gamma trilinear gauge couplings at sqrt(s) = 7 TeV are set.