IRC-safe jet flavour without modifying anything
Terry Generet
TL;DR
The paper tackles the NNLO breakdown of infrared–collinear safety in standard jet flavour definitions. It proposes a massification strategy that keeps the bottom quark mass at leading power and introduces process-independent soft functions $S$ to capture soft $b$-quark effects, preserving existing jet algorithms and cross sections. This yields IRC-safe predictions, with local cancellations of poles verified numerically and results implemented in Stripper. Phenomenological studies at the LHC show good agreement with other flavoured-jet approaches at high $p_T$ and highlight the role of mass effects and power corrections at low $p_T$, establishing the method's practicality and paving the way for broader NNLO flavoured-jet predictions.
Abstract
In this work, we describe how infrared-collinear safety can be restored perturbatively for standard definitions of jets and jet flavour. We will explicitly study this approach at next-to-next-to-leading order in QCD, where we will discuss the cause of the violation of infrared safety, argue that it is merely an artefact of the calculation, and explain how a consistent treatment of flavour removes this violation. The most important feature of our approach is that it does not require any changes to the definition of the jet or its flavour, nor does it modify the definition of the cross section. Consequently, the predictions can be directly compared to measurements performed using the standard anti-$k_T$ jet clustering algorithm, without the need for experimental collaborations to adapt their analyses to some new, infrared-collinear-safe definition of jet flavour, as would be the case for most - if not all - solutions presented in the literature thus far.