Azimuthally Differential Pion Femtoscopy in Pb-Pb Collisions at √sNN=2.76 TeV

Adamova, D. and Antičić, Tome and Erhardt, Filip and Gotovac, Sven and Jerčić, Marko and Lončar, P. and Mudnić, Eugen and Planinić, Mirko and Poljak, Nikola and Simatović, Goran and Utrobičić, Antonija and Vicković, Linda and Zmeskal, J. (ALICE Collaboration) (2017) Azimuthally Differential Pion Femtoscopy in Pb-Pb Collisions at √sNN=2.76 TeV. Physical Review Letters, 118 (22). pp. 222301-12. ISSN 0031-9007

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We present the first azimuthally differential measurements of the pion source size relative to the second harmonic event plane in Pb-Pb collisions at a center-of-mass energy per nucleon-nucleon pair of √sNN=2.76  TeV. The measurements have been performed in the centrality range 0%–50% and for pion pair transverse momenta 0.2<kT<0.7 GeV/c. We find that the Rside and Rout radii, which characterize the pion source size in the directions perpendicular and parallel to the pion transverse momentum, oscillate out of phase, similar to what was observed at the Relativistic Heavy Ion Collider. The final-state source eccentricity, estimated via Rside oscillations, is found to be significantly smaller than the initial-state source eccentricity, but remains positive—indicating that even after a stronger expansion in the in-plane direction, the pion source at the freeze-out is still elongated in the out-of-plane direction. The 3+1D hydrodynamic calculations are in qualitative agreement with observed centrality and transverse momentum Rside oscillations, but systematically underestimate the oscillation magnitude.

Item Type: Article
Date: 2 June 2017
Subjects: NATURAL SCIENCES > Physics
Additional Information: © 2017 CERN, for the ALICE Collaboration. Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Received 21 February 2017. Published 2 June 2017.
Divisions: Faculty of Science > Department of Physics
Publisher: American Physical Society
Depositing User: Gordana Stubičan Ladešić
Date Deposited: 20 Sep 2017 18:15
Last Modified: 20 Sep 2017 18:15

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