Mass depletion: a new parameter for quantitative jet modification

TL;DR

This paper introduces jet mass as a crucial parameter in classifying and understanding jet modification in heavy-ion collisions, emphasizing the importance of mass depletion alongside energy loss.

Contribution

It extends jet modification classification by incorporating jet mass, highlighting its impact on observables and the need to consider mass depletion for accurate comparisons.

Findings

Jet mass correlates closely with jet reconstruction outcomes.

Mass depletion significantly affects jet shape and fragmentation functions.

Differences in jet mass after medium traversal influence observable jet properties.

Abstract

We propose an extension to classify jet modification in heavy-ion collisions by including the jet mass along with its energy. The mass of a jet, as measured by jet reconstruction algorithms, is constrained by the jet's virtuality, which in turn has a considerable effect on such observables as the fragmentation function and jet shape observables. The leading parton, propagating through a dense medium, experiences substantial virtuality (or mass) depletion along with energy loss. Meaningful comparisons between surviving jets and jets produced in $p$-$p$ collisions require mass depletion to be taken into account. Using a vacuum event generator, we show the close relationship between the actual jet mass and that after applying a jet reconstruction algorithm. Using an in-medium event generator, we demonstrate the clear difference between the mass of a surviving parton exiting a dense medium and a parton with a similar energy formed in a hard scattering event. Effects of this difference on jet observables are discussed.