Top Quark Asymmetry in boosted single-lepton events at 13 TeV proton-proton collisions

The top quark plays a special role in many Beyond the Standard Model theories that predict new massive particles decaying into a top quark and a top anti-quark pair (tt). Depending on the momentum of massive particles (hundreds of GeV or a few TeV), the decay products may be distributed isotropically or highly collimated. This thesis presents the measurement of the charge asymmetry for highly boosted tt pairs decaying in the single lepton + jets topology. The analysis is performed using 138 fb-1 of data collected in pp collisions at s = 13 TeV with the CMS detector during Run 2 of the Large Hadron Collider. The event selection is optimized for tt pairs produced with large Lorentz- boosts resulting in non-isolated leptons and overlapping jets from the t -> bW -> bqq decay. The top quark charge asymmetry is measured for events with t ̄t invariant mass larger than 750 GeV and corrected for detector and acceptance effects using a binned maximum likelihood fit. The measured value of Ac_full = 0.0069 ± 0.0044(stat)+0.0065(syst) ± 0.0032(MCstat) is 0.0069 in good agreement with the standard model prediction at NNLO in perturbation theory with NLO electroweak corrections. Differential distributions for two invariant mass bins are also presented.