Jet coherence in QCD media: the antenna radiation spectrum

TL;DR

This paper derives a comprehensive gluon radiation spectrum for a high-energy partonic antenna moving through a dense QCD medium, accounting for both longitudinal and transverse color coherence effects, including the LPM effect and jet angular ordering.

Contribution

It provides a unified derivation of the gluon spectrum that includes both medium-induced and vacuum-like coherence effects, extending previous models.

Findings

The spectrum incorporates the Landau-Pomeranchuk-Migdal effect.

It describes the transition to independent radiation in opaque media.

The results clarify the onset of transverse decoherence in dense QCD media.

Abstract

We study the radiation of a highly energetic partonic antenna in a colored state traversing a dense QCD medium. Resumming multiple scatterings of all involved constituents with the medium we derive the general gluon spectrum which encompasses both longitudinal color coherence between scattering centers in the medium, responsible for the well known Landau-Pomeranchuk-Migdal (LPM) effect, and transverse color coherence between partons inside a jet, leading, in vacuum, to angular ordering of the parton shower. We discuss shortly the onset of transverse decoherence which is reached in opaque media. In this regime, the spectrum consists of independent radiation off the antenna constituents.