Two-pion Bose-Einstein correlations in Pb-Pb collisions at 2.76 TeV with ALICE

TL;DR

This paper reports the first measurement of pion source radii in Pb-Pb collisions at 2.76 TeV, revealing collective expansion effects and larger radii compared to lower-energy collisions, consistent with multiplicity scaling.

Contribution

It provides the first measurement of two-pion Bose-Einstein correlations at LHC energies, extending previous lower-energy studies and analyzing their dependence on transverse momentum.

Findings

Radii decrease with increasing transverse momentum.

Radii are larger than at RHIC, scaling with cube root of multiplicity.

Evidence of collective expansion in high-energy heavy-ion collisions.

Abstract

We present the first measurement of pion source radii in Pb-Pb collisions at the LHC. The radii were obtained by analyzing the Bose-Einstein enhancement in two-pion correlation functions. Like at lower energies, the radii drop with increasing transverse momentum, indicating presence of collective expansion. In absolute terms, all three radii (Rout, Rside, Rlong) are larger than at RHIC, roughly consistent with a linear scaling with the cube root of the particle multiplicity.