Probing jet hadrochemistry in Pb--Pb collisions with ALICE

TL;DR

This paper presents the first measurements of identified particle ratios within jets in Pb--Pb collisions, providing insights into jet quenching and medium response in the quark-gluon plasma using ALICE's particle identification capabilities.

Contribution

It introduces the first measurements of $ m{ ext{π}}, m{ ext{K}},$ and p ratios inside jets and in the underlying event in heavy-ion collisions, advancing understanding of jet-medium interactions.

Findings

Identified particle ratios within jets differ between Pb--Pb and pp collisions.

Results help distinguish jet fragmentation modifications from bulk medium effects.

Data constrains models of jet quenching and medium response.

Abstract

Jet substructure measurements in heavy-ion collisions provide constraints on jet quenching and the medium response in the QGP. Though there has been remarkable progress in inclusive-charged-hadron jet substructure measurements, understanding the identified particle composition of jets and their modification in heavy-ion collisions has proven challenging. Jet quenching models predict that the jet hadrochemical composition may be modified in heavy-ion collisions due to jet-medium interactions, as well as the medium response. Measurements of identified particles in jets can help discriminate between various parton-QGP interactions. We present the first measurements of $\pi$, K, and p ratios within charged-particle-jets, as well as in the underlying event, as a function of particle transverse momentum in pp and Pb--Pb collisions at $\sqrt{s_{\rm{NN}}}$ = 5.02 TeV. These measurements leverage the excellent PID capabilities of ALICE over a wide transverse momentum range. These results aim to understand soft particle production mechanisms and distinguish modified jet fragmentation from bulk effects.