Practical Jet Flavour Through NNLO

TL;DR

This paper introduces a novel, infrared and collinear safe jet flavour definition using Soft Drop grooming and Jade reclustering, compatible with NNLO calculations for precise QCD predictions.

Contribution

A new jet flavour definition that is IRC safe at NNLO, applicable to any parton collection and compatible with existing fixed-order calculations.

Findings

Proves IRC safety of the new jet flavour definition at NNLO.

Demonstrates that Soft Drop with Jade reclustering maintains IRC safety.

Shows that alternative methods like generalized kT fail at NNLO.

Abstract

An infrared and collinear (IRC) safe definition of the partonic flavour of a jet is vital for precision predictions of quantum chromodynamics at colliders. Jet flavour definitions have been presented in the literature, but they are typically defined through modification of the jet algorithm to be sensitive to partonic flavour at every stage of the clustering. While this does ensure that the sum of flavours in a jet is IRC safe, a flavour-sensitive clustering procedure is difficult to apply to realistic data. We introduce a distinct and novel approach to jet flavour that can be applied to any collection of partons defined by any algorithm. Our definition of jet flavour is the sum of flavours of all partons that remain after Soft Drop grooming, reclustered with the Jade algorithm. We prove that this prescription is IRC safe through next-to-next-to-leading order (NNLO), and so can interface with the most precise fixed-order calculations for jets available at present. We validate the IRC safety of this definition with numeric fixed-order codes and further show that jet flavour with Soft Drop reclustered with a generalised kT algorithm fails to be IRC safe at NNLO.