Associated production of W + charm in 13 TeV proton-proton collisions measured with CMS and determination of the strange quark content of the proton

This thesis presents the measurement of of associated production of a W${}^{\pm }$ boson and a charm quark (W + c) in proton-proton collisions at a center-of-mass energy of 13 TeV. The data used in this analysis has been recorded by the CMS experiment at the CERN LHC and corresponds to an integrated luminosity of 35.7 fb${}^{-1}$ . The W${}^{\pm }$ bosons are reconstructed by the presence of a muon and a neutrino, with the latter indicated by the missing transverse momentum in an event. Charm quarks are identified by the full reconstruction of D*(2010)${}^{\pm }$ mesons decaying via D*(2010)${}^{\pm }$ $\to$ D${}^0$ + ${\pi }^{\pm }$ $\to$ K${}^{\mp }$ + ${\pi }^{\pm }$ + ${\pi }^{\pm }$. The fiducial phase space of the measurement is defined by the muontransverse momentum p${}_T^{\mu }$ > 26 GeV, muon pseudorapidity $|$${\eta }^{\mu }$$|$ < 2.4 and the charm quark transverse momentum p${}_T^c$ > 5 GeV. The measurement is performed inclusivelyand differentially as a function of the absolute pseudorapidity of the muon from the W${}^{\pm }$ boson decay. The results are compared to theoretical predictions using different PDFsets. A subsequent QCD analysis is performed to extract the strange quark content of the proton and assess possible improvements in the uncertainties associated with thedistribution by including the new measurement. The extracted strange quark distribution is compared to distributions obtained in global PDF fits, which utilize the results ofneutrino scattering experiments.