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

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Abstract

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.

Journal

  • Physical review C

    Physical review C 93(2), 024905, 2016-02

    American Physical Society

Keywords

Codes

  • NII Article ID (NAID)
    120006545238
  • NII NACSIS-CAT ID (NCID)
    AA00773613
  • Text Lang
    ENG
  • Article Type
    journal article
  • ISSN
    2469-9985
  • Data Source
    IR 
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