Abstract
The production of a W boson in association with a single charm quark is studied using 4.6 fb^-1 of pp collision data at sqrt(s)=7 TeV collected with the ATLAS detector at the Large Hadron Collider. In events in which a W boson decays to an electron or muon, the charm quark is tagged either by its semileptonic decay to a muon or by the presence of a charmed meson. The integrated and differential cross sections as a function of the pseudorapidity of the lepton from the W-boson decay are measured. Results are compared to the predictions of next-to-leading-order QCD calculations obtained from various parton distribution function parameterisations. The ratio of the strange-to-down sea-quark distributions is determined to be 0.96 +0.26 -0.30 at Q^2=1.9 GeV^2, which supports the hypothesis of an SU(3)-symmetric composition of the light-quark sea. Additionally, the cross-section ratio sigma(W^+ + bar{c})/sigma(W^- + c) is compared to the predictions obtained using parton distribution function parameterisations with different assumptions about the s-bar{s} quark asymmetry.
Highlights
IntroductionThe production of a W boson in association with a single charm quark in proton-proton collisions is described at leading order (LO) in perturbative quantum chromodynamics (QCD)
The production of a W boson in association with a single charm quark in proton-proton collisions is described at leading order (LO) in perturbative quantum chromodynamics (QCD)by the scattering of a gluon and a down-type quark (d, s, b)
This paper presents a measurement of the production of a W boson in association with a single charm quark using 4.6 fb−1 of pp collision data at collected with the ATLAS detector at the Large Hadron Collider (LHC) in 2011
Summary
The production of a W boson in association with a single charm quark in proton-proton collisions is described at leading order (LO) in perturbative quantum chromodynamics (QCD). Since the gs → W c process and its higher-order corrections are dominant, the pp → W cX production is directly sensitive to the s-quark distribution function in the proton at momentum-transfer values on the order of the W -boson mass (mW ). The cross section is reported in a fiducial region where the above mentioned charmed hadron is required to decay semileptonically to a muon with pμT > 4 GeV and pseudorapidity |ημ| < 2.5 with ∆R < 0.5 from the jet axis. Differential cross sections are measured separately as a function of the D(∗)-meson transverse momentum pDT (∗) and of the pseudorapidity of the lepton from the W -boson decay |η |. All measurements are compared to predictions of NLO QCD calculations obtained with various PDF sets and the sensitivity to the choice of PDFs is presented
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