Practical jet flavour through NNLO

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 a 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 k(T) algorithm fails to be IRC safe at NNLO.

Automated summary

An infrared and collinear (IRC) safe definition of jet flavour is essential for accurate predictions in quantum chromodynamics at colliders. The existing flavour definitions for jets typically modify the jet algorithm to be sensitive to partonic flavour at each clustering stage, which is not practical for real data. We propose a novel approach to jet flavour that can be applied to any parton clustering algorithm, using Soft Drop grooming and JADE algorithm. We prove the IRC safety of this definition at NNLO, making it compatible with the most precise fixed-order calculations for jets.