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

Submission Date: 
17/04/2014
Article Information
Submission Form
System: 
p-p
System: 
Pb-Pb
System: 
p-Pb
Energy: 
2.76 TeV
Energy: 
5.02 TeV
Energy: 
7 TeV
Abstract Plain Text: 

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.

Supplemental figures note: https://cds.cern.ch/record/1971436