Measurement of the production cross section of a W boson in association with a charm quark in proton-proton collisions at $\sqrt{s}=13~\mathrm{TeV}$

The strange quark content of the proton is probed through the measurement of the production cross section of a W boson and a charm (c) quark in proton-proton collisions at a centre-of-mass energy of 13 TeV. The analysis uses a data sample corresponding to a total integrated luminosity of $138~\mathrm{fb}^{-1}$ collected by the CMS detector at the LHC. W bosons are identified through their leptonic decays to an electron or a muon, and a neutrino. Charm jets are tagged by the presence of a muon or a secondary vertex inside the jet. The $\mathrm{W}\!+\mathrm{c}$ production cross section and the cross section ratio $ \sigma({\rm W^+\! +\bar{c}}) / \sigma({\rm W^-\! +c})$ are measured inclusively and differentially as functions of the transverse momentum and the pseudorapidity of the lepton from the W boson decay. The measurements, with improved precision from previous CMS studies, are compared with theoretical predictions.