Freeze-out radii extracted from three-pion cumulants in pp, p–Pb and Pb–Pb collisions at the LHC

B. Abelev, J. Adam, D. Adamová, M.M. Aggarwal, Ian Bearden, Hans Bøggild, Christian Holm Christensen, Kristjan Herlache Gulbrandsen, Jens Jørgen Gaardhøje, Børge Svane Nielsen, Alexander Colliander Hansen, Ante Bilandzic, Marek Chojnacki, Valentina Zaccolo

44 Citations (Scopus)

Abstract

In high-energy collisions, the spatio-temporal size of the particle production region can be measured using the Bose-Einstein correlations of identical bosons at low relative momentum. The source radii are typically extracted using two-pion correlations, and characterize the system at the last stage of interaction, called kinetic freeze-out. In low-multiplicity collisions, unlike in high-multiplicity collisions, two-pion correlations are substantially altered by background correlations, e.g. mini-jets. Such correlations can be suppressed using three-pion cumulant correlations. We present the first measurements of the size of the system at freeze-out extracted from three-pion cumulant correlations in pp, p-Pb and Pb-Pb collisions at the LHC with ALICE. At similar multiplicity, the invariant radii extracted in p-Pb collisions are found to be 5-15% larger than those in pp, while those in Pb-Pb are 35-55% larger than those in p-Pb. Our measurements disfavor models which incorporate substantially stronger collective expansion in p-Pb as compared to pp collisions at similar multiplicity.

Original languageEnglish
JournalPhysics Letters B
Volume739
Pages (from-to)139-151
ISSN0370-2693
DOIs
Publication statusPublished - 2 Dec 2014

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