System and event activity dependent inclusive jet production with ALICE

TL;DR

This paper presents measurements of jet production and quenching effects in different collision systems at the LHC using ALICE data, revealing multiplicity-dependent jet behavior and collimation properties.

Contribution

It provides new systematic measurements of jet cross sections and nuclear modification factors across various multiplicity environments in pp and nucleus-nucleus collisions.

Findings

More jets are produced in high multiplicity events.

Jet production enhancement is weaker at higher jet $p_{\rm T}$ or resolution parameters.

Jets become more collimated at high $p_{\rm T}$, independent of collision energy or multiplicity.

Abstract

Jets are produced by processes involving high momentum transfer of initial partons at high energies. Comparing jet production in pp and nucleus-nucleus collisions will allow us to study the jet-quenching effect caused by the hot and dense QCD medium produced in nucleus-nucleus collisions when energetic partons traverse the medium. In particular, systematic studies of jet production in different multiplicity environments will provide in-depth understanding of the medium properties and their evolution from small to large systems. In small systems and high multiplicity events, the bulk properties extracted by the low transverse momentum particle production behaves as if a hot QCD medium was created, but such behaviour is not observed with hard probes. Study of jet production in different multiplicity proton-proton collisions then helps to explore the QGP existence in small systems. In this proceeding, the jet cross section measurements in different collision systems using the data taken by ALICE during the LHC Run 2 are presented. The nuclear modification factor of jets are presented to characterize the jet-quenching effect. We observe that more jets are produced in high multiplicity bins compared to the inclusive one, while the jet production enhancement in high multiplicity environments has weaker jet $p_{\rm T}$ or resolution parameter dependences. In order to study the jet collimation properties, the jet cross section ratios for different jet resolution parameters are also measured and compared to theoretical models. As expected, the jets get more collimated at high $p_{\rm T}$ in numerous multiplicity bins, with no collision energy or multiplicity dependence when compared to earlier results.