On angular ordering in medium-induced radiation

TL;DR

This paper investigates the angular structure of medium-induced gluon radiation in heavy-ion collisions, revealing an unexpected 'anti-angular ordering' effect that contrasts with vacuum behavior and impacts jet physics understanding.

Contribution

It introduces a calculation including interference effects in a medium, demonstrating an opposite angular ordering compared to the vacuum case.

Findings

Discovery of 'anti-angular ordering' in medium-induced radiation

Estimation of the effect's magnitude on jet physics

Implications for understanding energy loss in heavy-ion collisions

Abstract

Medium-induced gluon radiation gives rise to the strong energy-loss observed in single-hadron spectra in heavy-ion collisions. Its angular structure, leading e.g. to intra-jet correlations, is only known for the one-gluon inclusive case. In the vacuum, properties such as angular ordering appear when considering less inclusive distributions due to destructive interference effects. We present a calculation which takes into account interference effects in a medium for a setup in which we consider gluon radiation off a quark-antiquark pair with a given opening angle. Surprisingly, computing the spectrum at leading-log accuracy we find that an ordering exists which is exactly opposite from that in the vacuum. We estimate the magnitude of the effect along with a discussion of the implications of such "anti-angular ordering" on jet physics in heavy-ion collisions.