Azimuthally differential pion femtoscopy in Pb-Pb collisions at $\sqrt{s_{\rm NN}}=2.76$ TeV

Abstract : 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 $\sqrt{s_{\rm NN}}=2.76$ TeV. The measurements have been performed in the centrality range 0-50% and for pion pair transverse momenta $0.2 < k_{\rm T} < 0.7$ GeV/$c$. We find that the $R_{\rm side}$ and $R_{\rm out}$ 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 (RHIC). The final-state source eccentricity, estimated via $R_{\rm side}$ 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 $R_{\rm side}$ oscillations, but systematically underestimate the oscillation magnitude.
Type de document :
Pré-publication, Document de travail
SUBATECH-Plasma. 16 pages, 4 captioned figures, authors from page 11, figures at http://aliceinfo.cern.ch/ArtSubmi.. 2017
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http://hal.in2p3.fr/in2p3-01458788
Contributeur : Sylvie Flores <>
Soumis le : mardi 7 février 2017 - 07:51:19
Dernière modification le : mardi 16 janvier 2018 - 16:37:04

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  • HAL Id : in2p3-01458788, version 1
  • ARXIV : 1702.01612

Citation

D. Adamova, A. Baldisseri, H. Borel, J. Castillo Castellanos, J.L. Charvet, et al.. Azimuthally differential pion femtoscopy in Pb-Pb collisions at $\sqrt{s_{\rm NN}}=2.76$ TeV. SUBATECH-Plasma. 16 pages, 4 captioned figures, authors from page 11, figures at http://aliceinfo.cern.ch/ArtSubmi.. 2017. 〈in2p3-01458788〉

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