Topological studies of light-flavor hadron production in high multiplicity pp collisions with ALICE at the LHC

TL;DR

This paper investigates collective phenomena in high-multiplicity proton-proton collisions at 13 TeV using event shape observables, comparing results with models and exploring system size effects and jet quenching signatures.

Contribution

It introduces a detailed analysis of light-flavor hadron production using transverse spherocity and activity measures, providing new insights into soft-hard particle contributions and system size dependence in small collision systems.

Findings

Hadron-to-pion ratios vary with event shape and activity classes.

Average transverse momentum shows dependence on multiplicity and event shape.

No clear evidence of jet quenching in small systems was observed.

Abstract

Recent measurements in high-multiplicity pp and p-A collisions have revealed that these small collision systems exhibit collective-like behaviour, formerly thought to be achievable only in heavy-ion collisions. To understand the origins of these unexpected phenomena, event shape observables can be exploited, as they serve as a powerful tool to disentangle soft and hard contributions to particle production. Here, results on the production of light flavor hadrons for different classes of unweighted transverse spherocity ($S_{\rm 0}^{p_{\rm T}= 1}$) and relative transverse activity ($R_{\rm{T}}$) in high multiplicity pp collisions at $\sqrt{s}$ = 13 $\textrm{TeV}$ measured with the ALICE detector are presented. Hadron-to-pion ratios in different $S_{\rm 0}^{p_{\rm T}= 1}$ and $R_{\rm{T}}$ classes are also presented and compared with state-of-the-art QCD-inspired Monte Carlo event generators. The evolution of charged particle average transverse momentum ($\langle p_{\rm T}\rangle$) with multiplicity and $S_{\rm 0}^{p_{\rm T}= 1}$ is also discussed. In addition, the system size dependence of charged particle production in pp, p-Pb, and Pb-Pb collisions at $\sqrt{s_{\rm NN}}$= 5.02 TeV is presented. Finally, within the same approach, we present a search for jet quenching behavior in small collision systems.