Seminarium "Teoria cząstek elementarnych i kosmologia"

The mass of the top quark plays an important role in many predictions both within and beyond the standard model of particle physics. For instance, it is a central ingre- dient in the determination of the stability of the electroweak vacuum. However, quarks are never observed as free particles, and the pole mass defined as an analogue to a free particle’s mass suffers from an inherent theoretical ambiguity. This is avoided by using short-distance schemes, in which quark masses become renormalization scale de- pendent quantities. In the present work, the computation of the single-differential top quark-antiquark pair production cross section at next-to-leading order in the fixed-order expansion is examined consistently using the so-called MSR and modified minimal sub- traction schemes. A thorough investigation of the mass renormalization scale dependence of the pair invariant mass spectrum is carried out for the first time. The importance of a proper scale choice for obtaining robust cross-section predictions is discussed, and its effect on the extraction of the top quark mass from LHC data is demonstrated.