Extraction of jet-medium interaction details through jet substructure for inclusive and gamma-tagged jets

TL;DR

This paper investigates jet substructure modifications in heavy-ion collisions using inclusive and gamma-tagged jets, revealing that gamma-tagged jets are effective probes of medium-induced changes in jet splitting structures.

Contribution

It introduces a detailed analysis of jet substructure modifications with a focus on Soft Drop observables, highlighting the advantages of gamma-tagged jets in studying medium effects.

Findings

Inclusive jets show a slight narrowing in groomed splitting radius and mass distributions.

Gamma-tagged jets reveal genuine modifications in quark jet splitting structures.

Gamma-tagged jets are effective probes of medium-induced jet modifications.

Abstract

We present a comprehensive study of jet substructure modifications in high-energy heavy-ion collisions using both inclusive jets and $\gamma$-tagged jets, based on a multi-stage jet evolution model within the Monte Carlo framework JETSCAPE. To investigate hard parton splittings inside jets, we focus on Soft Drop observables. Our results for the groomed splitting radius and groomed jet mass distributions of inclusive jets show a slight narrowing compared to proton-proton baselines. We demonstrate that this apparent narrowing is primarily a selection bias from energy loss, rather than a direct modification of the splitting structure, by analyzing $\gamma$-tagged jets, where such bias is eliminated or significantly reduced. We also show that quark jets exhibit genuine modifications in their splitting structure, which is not seen in gluon jets. These effects are clearly visible in the substructure of $\gamma$-tagged jets, which are dominated by quark jets, but are not apparent for inclusive jets. This demonstrates that $\gamma$-tagged jets offer a powerful probe of medium-induced modifications to the hard splitting structure of jets.