Safe Use of Jet Pull

TL;DR

This paper introduces IRC safe projections of the jet pull vector, enabling better sensitivity to colour flow in Higgs decays while maintaining calculability, and compares theoretical predictions with simulations.

Contribution

It proposes IRC safe versions of the jet pull angle, providing a new tool for studying colour flow in particle physics analyses.

Findings

IRC safe pull angle distributions calculated to next-to-leading logarithmic accuracy.

Comparison shows good agreement between calculations and Monte Carlo simulations.

Asymmetry distributions can help assess subleading colour correlations in parton showers.

Abstract

Jet pull is an observable designed to probe colour flow between jets. Thus far, a particular projection of the pull vector, the pull angle, has been employed to distinguish colour flow between jets produced by a colour singlet or an octet decay. This is of particular importance in order to separate the decay of a Higgs boson to a pair of bottom quarks from the QCD background. However, the pull angle is not infra-red and collinear (IRC) safe. In this paper we introduce IRC safe projections of the pull vector that exhibit good sensitivity to colour flow, while maintaining calculability. We calculate these distributions to next-to-leading logarithmic accuracy, in the context of the hadronic decay of a Higgs boson, and compare these results to Monte Carlo simulations. This study allows us to define an IRC safe version of the pull angle in terms of asymmetry distributions. Furthermore, because of their sensitivity to wide-angle soft radiation, we anticipate that these asymmetries can play an important role in assessing subleading colour correlations and their modelling in general-purpose Monte Carlo parton showers.