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)± →
D0 +π± → K∓ +π± +π±. A cross section is measured in
the fiducial region defined by the muon transverse momentum pμ
T > 26 GeV, muon pseudorapidity |ημ| < 2.4, and
charm quark transverse momentum pc
T > 5 GeV. The inclusive cross section for this kinematic range is σ (W + c) =
1026 ± 31 (stat)+76
−72 (syst) 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.