Measurement of the production of a W boson in association with a charmed hadron in pp collisions at s√=13TeV with the ATLAS detector

The production of a W boson in association with a single charm quark is studied using 140 fb−1 of s√=13TeV proton-proton collision data collected with the ATLAS detector at the Large Hadron Collider. The charm quark is tagged by a charmed hadron, reconstructed with a secondary-vertex fit. The W boson is reconstructed from an electron/muon decay and the missing transverse momentum. The mesons reconstructed are D±→K∓π±π± and D∗±→D0π±→(K∓π±)π±, where pT(e,μ)>30GeV, |η(e,μ)|<2.5, pT(D)>8GeV, and |η(D)|<2.2. The integrated and normalized differential cross-sections as a function of the pseudorapidity of the lepton from the W boson decay, and of the transverse momentum of the meson, are extracted from the data using a profile likelihood fit. The measured fiducial cross-sections are σOS−SSfid(W−+D+)=50.2±0.2(stat.)+2.4−2.3(syst.)pb, σOS−SSfid(W++D−)=48.5±0.2(stat.)+2.3−2.2(syst.)pb, σOS−SSfid(W−+D∗+)=51.1±0.4(stat.)+1.9−1.8(syst.)pb, and σOS−SSfid(W++D∗−)=50.0±0.4(stat.)+1.9−1.8(syst.)pb. Results are compared with the predictions of next-to-leading-order quantum chromodynamics calculations performed using state-of-the-art parton distribution functions. The ratio of charm to anti-charm production cross-sections is studied to probe the s-s¯ quark asymmetry and is found to be R±c=0.971±0.006(stat.)±0.011(syst.).