Balance functions of (un)identified hadrons in Pb--Pb, p--Pb, and pp collisions at the LHC

TL;DR

This paper measures balance functions of identified and unidentified hadrons in various collision systems at the LHC to explore quark production, collective effects, and fragmentation, providing insights into the quark-gluon plasma and hadronization processes.

Contribution

It provides comprehensive measurements of balance functions for different hadrons across multiple collision systems and energies, testing models of quark production and collective behavior.

Findings

Balance functions vary with system size and energy.

Results support the two-wave quark production model.

Evidence of collective effects in high-multiplicity small systems.

Abstract

In ultrarelativistic heavy-ion collisions, correlations of particles with opposite quantum numbers provide insight into quark production mechanisms and time scales, collective motion, and re-scattering in the hadronic phase. The longitudinal and azimuthal widths of balance functions for charged kaons and charged pions are used to examine the two-wave quark production model proposed to explain quark-antiquark production within the QGP, which predicts a large increase in up and down quark pairs relative to strange quark pairs around the time of hadronization. Balance functions are also analyzed in small collision systems such as p--Pb and pp to study fragmentation effects and possible collective effects in high-multiplicity events. A comprehensive set of balance functions has been measured using the ALICE detector, including results for unidentified hadrons in Pb--Pb and p--Pb collisions at $\sqrt{s_{\rm{NN}}}=5.02$ TeV, for charged pions in Pb--Pb collisions at $\sqrt{s_{\rm{NN}}}=2.76$ TeV, p--Pb collisions at $\sqrt{s_{\rm{NN}}}=5.02$ TeV and pp collisions at $\sqrt{s}=7$ TeV, and for charged kaons in Pb--Pb collisions at $\sqrt{s_{\rm{NN}}}=2.76$ TeV. The first balance function yield results are also presented.