Measurement of charged and full jet production and nuclear modification factor in pp and p--Pb collisions with ALICE

TL;DR

This paper presents the most precise measurements of jet production and nuclear modification factors in pp and p--Pb collisions at LHC energies, enhancing understanding of QCD effects, cold nuclear matter, and jet quenching in small systems.

Contribution

It provides the most precise ALICE measurements of $R_{pPb}$ at 5.02 TeV, extending to lower jet transverse momentum and comparing cross-section ratios for different jet resolution parameters.

Findings

No jet quenching observed within current measurement precision.

Jet energy redistribution in cold nuclear matter is constrained.

Model predictions are compared to data, informing parton fragmentation mechanisms.

Abstract

The study of jet production in small collision systems is essential for testing our understanding of perturbative and non perturbative QCD and cold nuclear matter (CNM) effects. In addition, studies at high multiplicity in small collision systems exhibit signatures of collectivity, which is still not fully understood within a unified picture across system size. Jet quenching in small systems is not observed within current measurement precision, calling for more precise jet measurements. Results of charged particle and fully reconstructed jet production in pp and p--Pb collisions are presented at $\sqrt{s_{\rm NN}} = 5.02$ and $8$ TeV, along with the corresponding nuclear modification factor $R_{\rm pPb}$ at $\sqrt{s_{\rm NN}} = 5.02$ TeV. These results are the most precise measurements of the $R_{\rm pPb}$ by ALICE to date. To investigate whether jet energy is redistributed in CNM, the cross-section ratios for different jet resolution parameters ($R$) are compared between pp and p--Pb collisions, as well as within each collision system. Finally, comparisons between data and model predictions are discussed. This result extends previous LHC measurements to lower jet transverse momentum, constraining hard parton production and fragmentation mechanisms applied in model calculations, and the impact of the nuclear-modified parton distribution function on jet production. This measurement also provides new constraints on jet quenching in small collision systems.