Measurements of Inclusive and Differential Cross-sections of Single-top t-channel Production at p s = 8 TeV with the CMS Detector

Abstract

The Large Hadron Collider (LHC) is a top-quark factory, the large number of the topquarks are produced which can be used to measure various properties of the top-quark with a much higher precision. This thesis describes the single-top-quark t-channel inclusive and differential cross-section measurements in a proton-proton collisions at a center-of-mass energy of 8 TeV using lepton+jets in the final state. The results for the inclusive cross-section and the differential cross-section measurements are based on a data set which corresponds to an integrated luminosity of 19.7 fb􀀀1 recorded with the CMS detector at the LHC. The measured inclusive production cross-section of the t-channel single-top-quark is: st􀀀ch. = 83.6 2.3 (stat.) 7.4 (syst.) pb. The measured single t and t production cross-sections in the t-channel is: st􀀀ch.(t) = 53.8 1.5 (stat.) 4.4 (syst.) pb, st􀀀ch.(t) = 27.6 1.3 (stat.) 3.7 (syst.) pb. The measured cross-section ratio, top-quark(t) and the anti-top-quark(t), when separated on the basis of charged lepton at p s = 8 TeV is: Rt􀀀ch. = st􀀀ch.(t)/st􀀀ch.(t) = 1.95 0.10 (stat.) 0.19 (syst.), and the measurement of CKM matrix element, j fLvVtbj = 0.979 0.045 (exp.) 0.016 (theo.), comes out to be in good agreement with the standard model predictions. The single-topquark differential cross-section measurements as a function of the top-quark pT and jyj are performed. The differential cross-section measurements are essential for the comparison of the QCD predictions in the standard model. The measured normalized differential cross-sections come out to be in a remarkable agreement with the various theoretical predictions.