Jet Fragmentation at the LHC

Abstract

Run II at the LHC is pushing the energy and luminosity frontiers, and challenging the theory community to develop new tools both to increase the precision of our predictions and to expand their scope to match measurements of a more diverse set of observables. In this work, we describe the use of a new class of non-perturbative functions called Generalized Fragmentation Functions (GFFs) as a step towards these goals. This theoretical framework enables the calculation of a broad set of semi-inclusive jet observables. We explore known observables whose distributions can now be calculated using GFFs, and construct a new class of non-associative "fractal observables" which can be described with GFFs. As an important application, we calculate the spectrum of track-assisted mass, which can be measured experimentally with much better angular resolution than ordinary jet mass, including the effect of Soft-Drop grooming. In order to make connections to frameworks for describing Quantum Chromodynamics, we discuss the relationship between GFFs and the Generating Functional Approach (GFA).