p/pi Ratio in Di-Hadron Correlations

TL;DR

This study measures the p/pi ratio in di-hadron correlations in Pb--Pb collisions at 2.76 TeV, revealing differences between jet peak and bulk regions, and comparing with PYTHIA predictions to understand particle production mechanisms.

Contribution

It provides the first detailed measurement of the p/pi ratio in di-hadron correlations in heavy-ion collisions at LHC energies, distinguishing jet and bulk contributions.

Findings

p/pi ratio in bulk matches inclusive measurements

p/pi ratio in jet peak aligns with PYTHIA vacuum fragmentation

Bulk p/pi ratio is significantly larger than jet peak ratio

Abstract

Particle ratios are important observables used to constrain models of particle production in heavy-ion collisions. In this work we report on a measurement of the p/pi ratio in the transverse momentum range 2.0 < p_{T,assoc} < 4.0 GeV/c, associated with a charged trigger particle of 5.0 < p_{T,trig} < 10.0 GeV/c, in 0-10% central Pb--Pb collisions at sqrt{s_{NN}}=2.76 TeV. The ratio is measured in the jet peak and in a region at large Delta eta separation from the peak (bulk region). The presented results are based on 14M minimum-bias Pb--Pb collisions, recorded by the ALICE detector. It is observed that the p/pi ratio in the bulk region is compatible with the p/pi ratio of an inclusive measurement, and is much larger than the p/pi ratio in the jet peak. The p/pi ratio in the jet peak is compatible with a PYTHIA reference, in which fragmentation in the vacuum is the dominant mechanism of particle production.