Broadening in Medium-induced QCD Radiation off a $q {\bar q}$ Antenna

TL;DR

This paper calculates the one-gluon radiation spectrum from a massive quark-antiquark pair in a QCD medium, revealing interference effects that alter gluon broadening patterns compared to independent emitters.

Contribution

It introduces a calculation of medium-induced gluon radiation off a $q \bar{q}$ antenna, highlighting interference effects and their impact on gluon broadening.

Findings

Interference causes a different broadening pattern from independent emitters.

The gluon spectrum is collinear finite but infrared divergent at first order in opacity.

Interference effects modify the typical $\mathbf{k}$-broadening behavior.

Abstract

In this contribution, the one-gluon radiation spectrum off a massive quark-antiquark ($q {\bar q}$) antenna traversing a QCD medium is calculated in the eikonal approximation. The interference between emissions from the quark and the antiquark is considered. The gluon spectrum computed at first order in the opacity expansion is collinear finite but infrared divergent, which is in contrast with the result obtained from an independent emitter which is both infrared and collinear finite. Phenomenological consequences on the broadening of the emitted gluon are investigated. In the soft gluon emission limit, the interference between emitters causes a different broadening style from the typical {\bf k}-broadening in the case of an independent emitter.