Measurements of the associated production of a
W boson and a charm (c) quark in proton–proton collisions
at a centre-of-mass energy of 8 TeV are reported. The analysis uses a data sample corresponding to a total integrated
luminosity of 19.7 fb−1 collected by the CMS detector at
the LHC. The W bosons are identified through their leptonic
decays to an electron or a muon, and a neutrino. Charm quark
jets are selected using distinctive signatures of charm hadron
decays. The product of the cross section and branching fraction σ (pp → W + c + X)B(W → ν), where = e or μ,
and the cross section ratio σ (pp → W+ + ¯c + X)/σ (pp →
W− + c + X) are measured in a fiducial volume and differentially as functions of the pseudorapidity and of the transverse momentum of the lepton from the W boson decay. The
results are compared with theoretical predictions. The impact
of these measurements on the determination of the strange
quark distribution is assessed.