Azimuthally differential pion femtoscopy in Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}}}=2.76$ 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 $\sqrt{s_{\mathrm{NN}}}=2.76$ TeV. The measurements have been performed in the centrality range 0-50% and for pion pair transverse momenta $0.2<k_{\mathrm{T}}<0.7$ GeV/$c$. We find that the $R_{\mathrm{side}}$ and $R_{\mathrm{out}}$ 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 $R_{\mathrm{side}}$ 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 $R_{\mathrm{side}}$ oscillations, but systematically underestimate the oscillation magnitude.

arXiv comment16 pages, 4 captioned figures, authors from page 11, published version figures at http://aliceinfo.cern.ch/ArtSubmission/node/3419

References in corpus (23)

• Methods for analyzing anisotropic flow in relativistic nuclear collisions
• Performance of the ALICE Experiment at the CERN LHC
• Femtoscopy in Relativistic Heavy Ion Collisions: Two Decades of Progress
• Centrality dependence of the charged-particle multiplicity density at mid-rapidity in Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}}}$ = 2.76 TeV
• Performance of the ALICE VZERO system
• Observable implications of geometrical and dynamical aspects of freeze-out in heavy ion collisions
• Pion interferometry in Au+Au collisions at $\sqrt{{\mathrm{s}}_{{}_{\mathrm{NN}}}}$ = 200 GeV
• Observation of Anisotropic Event Shapes and Transverse Flow in Au+Au Collisions at AGS Energy
• Energy and Charged Particle Flow in 10.8 A GeV/c Au+Au Collisions
• Azimuthally sensitive Hanbury Brown-Twiss interferometry in Au+Au collisions at sqrt(s_{NN}) = 200 GeV
• Centrality dependence of pion freeze-out radii in Pb-Pb collisions at $\sqrt{{\mathbf{s}}_{\mathbf{NN}}}$=2.76 TeV
• Azimuthal Dependence of Pion Interferometry at the AGS
• Tilted Pion Sources from Azimuthally Sensitive HBT Interferometry
• Hbt Analysis of Anisotropic Transverse Flow
• Systematic study of charged-pion and kaon femtoscopy in Au$+$Au collisions at $\sqrt{s_{{}_{NN}}}$=200 GeV
• Anisotropic Transverse Flow and the HBT Correlation Function
• Shape analysis of strongly-interacting systems: the heavy ion case
• HBT interferometry relative to the triangular flow plane in heavy-ion collisions
• Azimuthally sensitive femtoscopy in event-by-event hydrodynamics
• Femtoscopy of the system shape fluctuations in heavy ion collisions
• Azimuthal-angle dependence of charged-pion-interferometry measurements with respect to 2${}^{\mathrm{nd}}$- and $3^{\mathrm{rd}}$-order event planes in Au$+$Au collisions at $\sqrt{s_{{}_{NN}}}=200$ GeV
• Viscous Flow in Heavy-Ion Collisions from RHIC to LHC
• Initial conditions from the shadowed Glauber model for Pb+Pb at $\sqrt{s_{\mathrm{NN}}}=2.76$ TeV

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