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Centrality dependence of pion freeze-out radii in Pb-Pb collisions at √ s N N = 2.76 TeV
ALICE Collaboration Adam, J. Tapia Takaki, Daniel
ALICE Collaboration
Adam, J.
Tapia Takaki, Daniel
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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 onedimensional 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.
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2016-02-04
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American Physical Society
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J. Adam et al. ALICE Collaboration. Phys. Rev. C 93, 024905 (2016) https://doi.org/10.1103/PhysRevC.93.024905