Particle production as a function of underlying-event activity and search for jet-like modifications in pp, p-Pb, and Pb-Pb collisions at $\sqrt{s_{\rm NN}}=5.02$ TeV with ALICE

TL;DR

This study investigates particle production and potential jet modifications across different collision systems at 5.02 TeV, using underlying event activity to compare small and large systems and testing models against experimental data.

Contribution

It introduces a method to compare small- and large-collision systems using underlying event activity and searches for jet-like modifications in pp, p-Pb, and Pb-Pb collisions at 5.02 TeV.

Findings

No significant jet-like modifications observed in small systems.

Charged-particle production scales with underlying event activity.

Model comparisons show varying agreement with data.

Abstract

The similarity between small- and large-collision systems is explored using the charged-particle multiplicity in the transverse region, $N^{\rm T}_{\rm ch}$, which is sensitive to the underlying event. Measurements of charged-particle production as a function of $N^{\rm T}_{\rm ch}$ in pp, p-Pb and Pb-Pb collisions at $\sqrt{s_{\rm NN}}=5.02$ TeV in the toward, away and transverse regions are discussed. These three regions are defined relative to the track with the largest transverse momentum in the event ($p_{\rm T}^{\rm trig}$). The activity in the transverse region is subtracted from the activity in the toward and the away regions to search for jet-like modifications in small-collision systems. The jet-like signals are studied both as a function of $N^{\rm T}_{\rm ch}$ and $p_{\rm T}^{\rm trig}$. Results are compared with two general purpose Monte Carlo event generators: PYTHIA~8 and EPOS~LHC.