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), 024905. doi:10.1103/PhysRevC.93.024905
Published inPhysical Review C
Rak, Jan |
©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. ...