Measurement of associated production of a W boson and a charm quark in proton-proton collisions at sqrt(s) = 13 TeV

Measurements are presented of associated production of a W boson and a charm quark (W + c) in proton-proton collisions at a center-of-mass energy of 13 TeV. The data correspond to an integrated luminosity of 35.7 fb(-1) collected by the CMS experiment at the CERN LHC. The W bosons are identified by their decay into a muon and a neutrino. The charm quarks are tagged via the full reconstruction of D* (2010)(+/-) mesons that decay via D*(2010)(+/-) D-0 + pi(+/-) -> K--/+ + pi(+/-) + pi(+/-). A cross section is measured in the fiducial region defined by the muon transverse momentum p(T)(mu) > 26 GeV, muon pseudorapidity vertical bar eta(mu)vertical bar < 2.4, and charm quark transverse momentum p(T)(c) > 5 GeV. The inclusive cross section for this kinematic range is sigma(W + c) = 1026 +/- 31(stat)(-72)(+76) pb. The cross section is also measured differentially as a function of the pseudorapidity of the muon from the W boson decay. These measurements are compared with theoretical predictions and are used to probe the strange quark content of the proton.