NLO and off-shell effects in top quark mass determinations

TL;DR

This paper investigates how different theoretical models of top quark pair production affect the accuracy of top quark mass measurements, comparing full NLO corrections with various decay approximations.

Contribution

It provides a detailed comparison of NLO and off-shell effects on top quark mass determination, highlighting the impact of different decay modeling approaches.

Findings

Off-shell effects can cause measurable shifts in top mass measurements.

Different decay approximations lead to variations in the calibration of mass extraction.

Full NLO calculations improve the precision of top quark mass determination.

Abstract

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 $pp\rightarrow W^+W^-b\bar b\rightarrow (e^+ \nu_e)\,(\mu^- \bar{\nu}_{\mu})\,b\bar b$ 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.