QCD jets in a hot and dense medium: a study of shower formation time and collision kernels

TL;DR

This paper uses the MARTINI model to study how incorporating formation time and different collision kernels affect jet quenching observables in a hot, dense QCD medium, improving agreement with experimental data.

Contribution

It introduces the importance of formation time in jet shower modeling and compares various collision kernels within MARTINI for their impact on jet substructure observables.

Findings

Formation time improves simultaneous description of R_{AA} for hadrons and jets.

Different collision kernels cause sizable variations in jet shape and fragmentation functions.

Soft gluon radiation rates significantly influence jet substructure modifications.

Abstract

With the use of MARTINI, a model which considers evolving QCD jets against a fluid dynamical background, it is shown that the introduction of formation time to the parton shower after the initial hard scattering is essential for a simultaneous description of charged hadron and jet $R_{AA}$. This inclusion also improves jet shape ratio at small angle and jet fragmentation function ratios of leading charged hadrons. The MARTINI framework is then aimed at a study of the leading order, next-to-leading-order, and non perturbative collision kernels. Sizable differences in the modification of jet substructure observables, i.e., jet shape and fragmentation functions are observed. Such differences are caused by the difference in the radiation rates of relatively soft gluons that survive in the evolution in medium.