Abstract
We report on the measurement of freeze-out radii for pairs of identical-charge pions measured in Pb-Pb collisions at TeV as a function of collision centrality and the average transverse momentum of the pair . Three-dimensional sizes of the system (femtoscopic radii), as well as direction-averaged one-dimensional radii are extracted. The radii decrease with , 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 . This behavior is compared to world data on femtoscopic radii in heavy-ion collisions. While the dependence is qualitatively similar to results at smaller , a decrease in the ratio 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.
2 More- Received 29 July 2015
DOI:https://doi.org/10.1103/PhysRevC.93.024905
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©2016 CERN, for the ALICE Collaboration