Differential Cross Sections for Top-Quark-Pair Production in the e/$\mu$+Jets Final State at $\sqrt{s} = 8$ TeV in CMS

The large number of top quarks produced in proton-proton (pp) collisions at the LargeHadron Collider facilitates precision measurements of top-quark properties that are crucialfor testing the consistency of the Standard Model (SM) of particle physics. In particular,differential measurements of the top-quark pair (tt) production cross section are essentialfor comparison with state-of-the-art predictions of Quantum Chromodynamics (QCD)within the SM and for searches for new physics phenomena beyond it. In this thesis,normalised differential tt cross sections are measured at a pp centre-of-mass energy of√s = 8 TeV. The analysed dataset is recorded by the CMS experiment and correspondsto an integrated luminosity of 19.7 fb−1 . The tt production cross section is measureddifferentially as a function of eighteen kinematic quantities of the top quarks and theirdecay products. The achieved precision of typically 3 − 7 % allows to distinguish betweendifferent QCD predictions for several of the analysed quantities. In particular, the measuredtt production cross section as a function of the top-quark transverse momentum and itsimpact on different top-quark related measurements, also outside the scope of this work,is discussed in detail. In addition, the top-quark mass is determined from the normaliseddifferential cross section as a function of the invariant mass of the tt system and oneadditional jet. The obtained result is compatible with other measurements, including theworld-average top-quark mass, within the achieved precision of about 1.5 %.