Groomed jets in heavy-ion collisions: sensitivity to medium-induced bremsstrahlung

TL;DR

This paper explores how jet substructure techniques, especially soft drop declustering, can be used to directly measure medium-induced gluon radiation in heavy-ion collisions, revealing insights into jet quenching mechanisms.

Contribution

It introduces a novel approach using soft drop declustering to probe medium-induced gluon bremsstrahlung and discusses its sensitivity to different energy loss mechanisms in heavy-ion collisions.

Findings

Enhanced energy fraction distribution at small subjets due to medium radiation

Sensitivity of the two-pronged probability ratio to energy loss mechanisms

Discussion of effects like colour decoherence and background contamination

Abstract

We argue that contemporary jet substructure techniques might facilitate a more direct measurement of hard medium-induced gluon bremsstrahlung in heavy-ion collisions, and focus specifically on the "soft drop declustering" procedure that singles out the two leading jet substructures. Assuming coherent jet energy loss, we find an enhancement of the distribution of the energy fractions shared by the two substructures at small subjet energy caused by hard medium-induced gluon radiation. Departures from this approximation are discussed, in particular, the effects of colour decoherence and the contamination of the grooming procedure by soft background. Finally, we propose a complementary observable, that is the ratio of the two-pronged probability in Pb-Pb to proton-proton collisions and discuss its sensitivity to various energy loss mechanisms.