A measurement of the ratio of the W and Z cross sections with exactly one associated jet in pp collisions at sqrt(s) = 7 TeV with ATLAS

TL;DR

This paper measures the ratio of W to Z boson production with exactly one jet at 7 TeV, comparing results with QCD predictions and finding good agreement within uncertainties.

Contribution

It provides a precise measurement of the W/Z cross section ratio with one jet, reducing uncertainties and comparing with advanced QCD models.

Findings

Measured ratio for electron channel: 8.73 +/- 0.30 (stat) +/- 0.40 (syst)

Measured ratio for muon channel: 8.49 +/- 0.23 (stat) +/- 0.33 (syst)

Results agree with QCD predictions within uncertainties

Abstract

The ratio of production cross sections of the W and Z bosons with exactly one associated jet is presented as a function of jet transverse momentum threshold. The measurement has been designed to maximise cancellation of experimental and theoretical uncertainties, and is reported both within a particle-level kinematic range corresponding to the detector acceptance and as a total cross-section ratio. Results are obtained with the ATLAS detector at the LHC in pp collisions at a centre-of-mass energy of 7 TeV using an integrated luminosity of 33 pb^-1. The results are compared with perturbative leading-order, leading-log, and next-to-leading-order QCD predictions, and are found to agree within experimental and theoretical uncertainties. The ratio is measured for events with a single jet with p_T > 30 GeV to be 8.73 +/- 0.30 (stat) +/- 0.40 (syst) in the electron channel, and $ 8.49 +/- 0.23 (stat) +/- 0.33 (syst) in the muon channel.