NLO and off-shell effects in top quark mass determinations

A bstract We study the impact of different theoretical descriptions of top quark pair production on top quark mass measurements in the di-lepton channel. To this aim, the full NLO corrections to pp→ W⁺W⁻bb̄→ (e⁺νₑ)(μ⁻ν̄μ)bb̄ pp → W + W − b b ¯ → e + ν e μ − ν ¯ μ b b ¯ production are compared to calculations in the narrow width approximation, where the production of a top quark pair is calculated at NLO and combined with three different descriptions of the top quark decay: leading order, next-to-leading order and via a parton shower. The different theory predictions then enter the calibration of template fit functions, which are used for a fit to pseudo-data. The offsets in the top quark mass resulting from the fits based on the various theoretical descriptions are determined.