Measurement of the W boson production in association with jets using √s = 8TeV proton-proton collisions atthe ATLAS detector

Abstract

The production of W bosons in association with jets serves as a precision test of perturbative quantum chromodynamics (pQCD). Split into W⁺ and W⁻ production, it provides access to the valence quark composition in the proton. The measurement of W + jets production presented here uses 20.3fb⁻¹ of proton-proton collision data at a center-of-mass energy of √s = 8TeV recorded with the ATLAS detector. The cross section measurement is performed in the decay channel W → eν for the charge-independent W production as well as W⁺ and W⁻ production separately, as a function of the jet multiplicity and differentially as a function of six observables in association with at least one or two jets. The results are compared to leading-order multi-leg and next-to-leading order pQCD calculations. The cross section ratio (W⁺ + jet)/(W⁻ + jet) is shown to be sensitive to the ratio of valence quark distribution functions in the proton, in a range of the momentum fraction x ∼ 0.1 − 0.5. This range is accessible so far mainly by fixed-target deep inelastic scattering experiments and the W asymmetry measurements at the Tevatron. The ratio of W⁺ to W⁻ production is measured as a function of the jet multiplicity and six observables in the presence of at least one or at least two jets, providing essential input to global fits of parton distribution functions.