Differential single-top-quark cross sections in t channel at 8 and 13 TeV with the CMS detector

The production of single top quarks in high energy collision events is a unique process to investigate the strength and structure of electroweak interactions. This thesis encompasses first measurements of differential single-top-quark cross sections in t channel which have been performed using data collected at center-of-mass energies of 8 and 13 TeV with the CMS detector at CERN, Switzerland. The electroweak coupling structure of the standard model of particle physics predicts only left-handed top quarks or right-handed top antiquarks to participate in electroweak interactions, resulting in the production of highly polarized top quarks via t channel. The degree of polarization is studied by measuring the cross section as a function of the polarization angle, defined as the angle between the charged lepton from the top quark decay and a spectator quark which is produced in association with the top quark. The differential cross section as a function of the polarization angle is measured in 8 TeV data. The top quark spin asymmetry, a quantity related to the polarization, is extracted from the differential cross section and the derivation of limits on potential anomalous top quark couplings occurring in new physics models is illustrated. In the second part, an early measurement of differential cross sections as a function of the top quark transverse momentum and rapidity is presented using the first data recorded at a center-of-mass energy of 13 TeV.