Pushing forward jet substructure measurements in heavy-ion collisions

TL;DR

This paper investigates jet substructure in heavy-ion collisions to identify medium-induced effects like color decoherence, proposing measurements at forward rapidities to minimize biases and provide clearer insights into quark-gluon plasma properties.

Contribution

It introduces a method to reduce selection biases in jet measurements and suggests using rapidity dependence to unambiguously detect color decoherence effects.

Findings

Heavy-ion jets are narrower than vacuum jets at mid-rapidity.

Narrowing effects may persist at forward rapidities where quark jets dominate.

Forward rapidity measurements could confirm color decoherence in quark-gluon plasma.

Abstract

Energetic jets that traverse the quark-gluon plasma created in heavy-ion collisions serve as excellent probes to study this new state of deconfined QCD matter. Presently, however, our ability to achieve a crisp theoretical interpretation of the crescent number of jet observables measured in experiments is hampered by the presence of selection biases. The aim of this work is to minimise those selection biases associated to the modification of the quark- vs. gluon-initiated jet fraction in order to assess the presence of other medium-induced effects, namely color decoherence, by exploring the rapidity dependence of jet substructure observables. So far, all jet substructure measurements at mid-rapidity have shown that heavy-ion jets are narrower than vacuum jets. We show both analytically and with Monte Carlo simulations that if the narrowing effect persists at forward rapidities, where the quark-initiated jet fraction is greatly increased, this could serve as an unambiguous experimental observation of color decoherence dynamics in heavy-ion collisions.