Centrality dependence of pion freeze-out radii in Pb-Pb collisions at √sNN = 2.76 TeV
ALICE Collaboration. (2016). Centrality dependence of pion freeze-out radii in Pb-Pb collisions at √sNN = 2.76 TeV. Physical Review C, 93(2), Article 024905. https://doi.org/10.1103/PhysRevC.93.024905
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2016Copyright
©2016 CERN, for the ALICE Collaboration. Published by the American Physical Society under the terms of the Creative Commons Attribution 3.0 License.
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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Except where otherwise noted, this item's license is described as ©2016 CERN, for the ALICE Collaboration. Published by the American Physical Society under the terms of the Creative Commons Attribution 3.0 License.
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