Elsevier

Physics Letters B

Volume 739, 12 December 2014, Pages 139-151
Physics Letters B

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

https://doi.org/10.1016/j.physletb.2014.10.034Get rights and content
Under a Creative Commons license
open access

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.

Cited by (0)

i

Also at: St. Petersburg State Polytechnical University.

ii

Deceased.

iii

Also at: Department of Applied Physics, Aligarh Muslim University, Aligarh, India.

iv

Also at: M.V. Lomonosov Moscow State University, D.V. Skobeltsyn Institute of Nuclear Physics, Moscow, Russia.

v

Also at: University of Belgrade, Faculty of Physics and “Vinča” Institute of Nuclear Sciences, Belgrade, Serbia.

vi

Permanent Address: Konkuk University, Seoul, South Korea.

vii

Also at: Institute of Theoretical Physics, University of Wroclaw, Wroclaw, Poland.

viii

Also at: University of Kansas, Lawrence, KS, United States.

E-mail address: [email protected].