Two-pion Bose-Einstein correlations in Pb-Pb collisions at sqrt(s_NN) = 2.76 TeV measured with the ALICE experiment

TL;DR

This paper reports on measurements of pion source radii in Pb-Pb collisions at 2.76 TeV using the ALICE experiment, revealing larger source sizes at LHC and evidence of collective expansion, which constrains dynamical models of medium evolution.

Contribution

First measurement of pion Bose-Einstein correlations at LHC energies, providing new insights into source size and expansion dynamics in heavy-ion collisions.

Findings

Source radii larger at LHC than at RHIC

Source radii decrease with pair momentum, indicating expansion

Results suggest higher temperature and longer lifetime of the fireball

Abstract

The measurement of pion source radii in Pb-Pb collisions with the ALICE experiment at LHC is presented. By the analysis of Bose-Einstein enhancement in the correlation function of identical pions information on the size and evolution of the source region in space-time can be obtained. The source radii observed at LHC are larger than at RHIC, approximately scaling with the cube root of the particle multiplicity. A decrease of source radii with increasing pair momentum, indicating a collective expansion of the medium, was observed at RHIC and SPS and is also expected at LHC energies. The ALICE data confirm this and provide strict constraints on dynamical models describing the medium expansion. The results suggest that the created fireball has a higher temperature and a longer lifetime as compared to lower energies.