2014/12/11 by Hoang, André H.
#FOS: Physical sciences #High Energy Physics - Phenomenology (hep-ph)
paper · doi:10.48550/arxiv.1412.3649
Currently the most precise LHC measurements of the top quark mass are determinations of the top quark mass parameter of Monte-Carlo (MC) event generators reaching uncertainties of well below 1 GeV. However, there is an additional theoretical problem when using the MC top mass mt\rm MC as an input for theoretical predictions, because a rigorous relation of mt\rm MC to a renormalized field theory mass is, at the very strict level, absent. In this talk I show how - nevertheless - some concrete statements on mt\rm MC can be deduced assuming that the MC generator behaves like a rigorous first principles QCD calculator for the observables that are used for the analyses. I give simple conceptual arguments showing that in this context mt\rm MC can be interpreted like the mass of a heavy-light top meson, and that there is a conversion relation to field theory top quark masses that requires a non-perturbative input. The situation is in analogy to B physics where a similar relation exists between experimental B meson masses and field theory bottom masses. The relation gives a prescription how to use mt\rm MC as an input for theoretical predictions in perturbative QCD. The outcome is that at this time an additional uncertainty of about 1 GeV has to be accounted for. I discuss limitations of the arguments I give and possible ways to test them, or even to improve the current situation.