A Measurement of the $W\gamma$ cross section at $\sqrt s = 8~$TeV in pp Collisions with the CMS Detector

A measurement of cross section of the $W\gamma\rightarrow l\nu\gamma$ production in proton-proton collisions using 19.6~fb$^{-1}$ of LHC data collected by CMS detector at the center-of-mass collision energy of $\sqrt{s}=8$~TeV is reported. The $W$ bosons are identified in their electron and muon decay modes. The process of $W\gamma$ production in the Standard Model (SM) involves a pure gauge boson coupling, a $WW\gamma$ vertex, which allows one to test the electroweak sector of the SM in a unique way not achievable by studies of other processes. In addition to the total cross section, we measure the differential cross section of $W\gamma$ production as a function of a photon transverse momentum. The measurement of the differential cross section is a sensitive probe for new physics originating from an anomalous gauge coupling because possible effects of its presence increase with the photon transverse momentum and, thus, are more likely to be observed in the differential than in the total cross section. The results of this measurement agree with the Standard Model prediction at NLO in QCD, and no evidence of an anomalous triple gauge coupling has been observed. The reported total cross section measurement is the first measurement of this quantity at the~8~TeV collision energy with CMS data. The differential cross section measurement discussed in this dissertation is the first ever measurement of this process performed by CMS since the start of the LHC.