Vacuum-like jet fragmentation in a dense QCD medium

TL;DR

This paper investigates how a dense quark-gluon plasma affects jet fragmentation, revealing reduced phase-space and angular ordering violations, with results aligning qualitatively with LHC measurements.

Contribution

It introduces the first calculation of medium effects on vacuum-like emissions in jet fragmentation using a double-logarithmic approximation.

Findings

Reduced phase-space for in-medium emissions

First outside-medium emission can violate angular ordering

Qualitative agreement with LHC jet fragmentation data

Abstract

We study the fragmentation of a jet propagating in a dense quark-gluon plasma. Using a leading, double-logarithmic approximation in perturbative QCD, we compute for the first time the effects of the medium on the vacuum-like emissions. We show that, due to the scatterings off the plasma, the in-medium parton showers differ from the vacuum ones in two crucial aspects: their phase-space is reduced and the first emission outside the medium can violate angular ordering. We compute the jet fragmentation function and find results in qualitative agreement with measurements at the LHC.