Monte Carlo Top Quark Mass Calibration

Bahman Dehnadi, André H. Hoang, Vicent Mateu, Moritz Preißer, Ian Stewart

The most precise top quark mass measurements use kinematic reconstruction methods, determining the top mass parameter of a Monte Carlo event generator, mMCt. Due to the complicated interplay of hadronization and parton shower dynamics in Monte Carlo event generators relevant for kinematic reconstruction, relating mMCt to field theory masses is a non-trivial task. In this talk we report on a calibration procedure to determine this relation using hadron level QCD predictions for 2-Jettiness in e+e− annihilation, an observable which has kinematic top mass sensitivity and a close relation to the invariant mass of the particles coming from the top decay. The theoretical ingredients of the QCD prediction are reviewed. Fitting e+e− 2-Jettiness calculations at NLL/NNLL order to \Pythia~8.205, we find that mMCt agrees with the MSR mass mMSRt,1GeV within uncertainties. At NNLL we find mMCt=mMSRt,1GeV+(0.18±0.22)GeV. mMCt can differ from the pole mass mpolet by up to 600MeV, and using the pole mass generally leads to larger uncertainties. At NNLL we find mMCt=mpolet+(0.57±0.28)GeV as the fit result. In contrast, converting mMSRt,1GeV obtained at NNLL to the pole mass gives a result for mpolet that is substantially larger and incompatible with the fit result. We also explain some theoretical aspects relevant for employing the C-parameter as an alternative calibration observable.

Particle Physics
External organisation(s)
Universität Siegen, Erwin Schrödinger Institut, Universidad de Salamanca, Consejo Superior de Investigaciones Científicas (CSIC), Massachusetts Institute of Technology
Proceedings of Science (PoS)
No. of pages
Publication date
Peer reviewed
Austrian Fields of Science 2012
103024 Quantum field theory
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