Non-perturbative QCD Effects and the Top Mass at the Tevatron

TL;DR

This paper investigates how non-perturbative QCD effects, modeled via a string-based reconnection toy model in Pythia, influence the precision of top quark mass measurements at the Tevatron, estimating an uncertainty of about 0.5 GeV.

Contribution

It introduces a universal toy model for non-perturbative color reconnections in collider simulations and assesses its impact on top mass measurements.

Findings

Non-perturbative effects can cause about ±0.5 GeV uncertainty in top mass measurements.

Recent Pythia updates influence the tuning and results of the non-perturbative model.

The study provides updated estimates of non-perturbative uncertainties in top mass analyses.

Abstract

The modelling of non-perturbative effects is an important part of modern collider physics simulations. In hadron collisions there is some indication that the modelling of the interactions of the beam remnants, the underlying event, may require non-trivial colour reconnection effects to be present. We recently introduced a universally applicable toy model of such reconnections, based on hadronising strings. This model, which has one free parameter, has been implemented in the Pythia event generator. We then considered several parameter sets (`tunes'), constrained by fits to Tevatron minimum-bias data, and determined the sensitivity of a simplified top mass analysis to these effects, in exclusive semi-leptonic top events at the Tevatron. A first attempt at isolating the genuine non-perturbative effects gave an estimate of order +-0.5GeV from non-perturbative uncertainties. The results presented here are an update to the original study and include recent bug fixes of Pythia that influenced the tunings investigated.