The Top Mass

André H. Hoang

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 mMCt as an input for theoretical predictions, because a rigorous relation of mMCt to a renormalized field theory mass is, at the very strict level, absent. In this talk I show how - nevertheless - some concrete statements on mMCt 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 mMCt 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 mMCt 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.

Particle Physics
Publication date
Austrian Fields of Science 2012
103034 Particle physics
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