Measurement of t-tbar Forward-backward Asymmetry in Large Hadron Collider

Abstract

This thesis presents a measurement of Forward-Backward Asymmetry($\AFB$) in $\ttbar$ production. The data sample corresponds to $19.7\,\textrm{fb}^{-1}$ of integrated luminosity in proton-proton collisions at $\sqrt{s} = 8\,\textrm{TeV}$ collected by the CMS experiment at the LHC. Events selected contain a single isolated muon or electron, with four or five jets of which two are b-tagged. A template technique is used to extract the asymmetry from the top quark kinematic distributions. This technique is based upon an extension of the tree-level cross section for $\qqbar$ initial states that sensitively isolates $\qqbar$ from $\mathrm{gg/qg}$ initial states. The measured $\AFB$ and relative aboundance of $\qqbar$ initiated $\ttbar$ are measured and compared to both theoretical calculation and results from D0 and CDF experiments of Tevatron.