Centrality dependence of pion freeze-out radii in Pb-Pb collisions at sNN =2.76 TeV

Summary, in English

We report on the measurement of freeze-out radii for pairs of identical-charge pions measured in Pb-Pb collisions at sNN=2.76 TeV as a function of collision centrality and the average transverse momentum of the pair kT. Three-dimensional sizes of the system (femtoscopic radii), as well as direction-averaged one-dimensional radii are extracted. The radii decrease with kT, following a power-law behavior. This is qualitatively consistent with expectations from a collectively expanding system, produced in hydrodynamic calculations. The radii also scale linearly with (dNch/dη)1/3. This behavior is compared to world data on femtoscopic radii in heavy-ion collisions. While the dependence is qualitatively similar to results at smaller sNN, a decrease in the ratio Rout/Rside is seen, which is in qualitative agreement with a specific prediction from hydrodynamic models: a change from inside-out to outside-in freeze-out configuration. The results provide further evidence for the production of a collective, strongly coupled system in heavy-ion collisions at the CERN Large Hadron Collider. © 2016 CERN.

• Author: Adam J.; P. Christiansen; H. Ljunggren; A. Oskarsson; T. Richert; D. Silvermyr; C. Søgaard; E. Stenlund; V. Vislavicius; Zyzak M.
• Department/s: Particle and nuclear physics; eSSENCE: The e-Science Collaboration
• Publishing year: 2016
• Language: English
• Publication/Series: Physical Review C
• Volume: 93
• Issue: 2
• Links: http://dx.doi.org/10.1103/PhysRevC.93.024905
• Document type: Journal article
• Publisher: American Physical Society
• Topic: Subatomic Physics
• Status: Published
• ISBN/ISSN/Other: ISSN: 2469-9985