Preparatory studies on the determination of the top-quark mass in single top-quark events with the ATLAS detector at the LHC

In this thesis, a measurement of the single top quark mass produced in the t -channel is presented, using the data sample recorded recently in 2015 with the ATLAS detector at the LHC, at a centre of mass energy of √ s = 13 TeV and corresponding to an integrated luminosity of 3.2 f b−1 . The selected events contain one charged lepton (electron or muon), missing transverse energy, and two jets with high transverse momentum with one of them being b-tagged. The template method is used to extract the top quark mass from the distribution of the invariant mass of the lepton and the b-jet (m(`b)) in the selected events. The result of the measured top quark mass is: mtop = [174.56 ± 3.11(syst.) ± 1.02(stat.)] GeV.