Directed flow of charged particles at mid-rapidity relative to the spectator plane in Pb-Pb collisions at $\sqrt{s_\rm{NN}}$=2.76 TeV

Abstract

The directed flow of charged particles at mid-rapidity is measured in Pb-Pb collisions at $\sqrt{s_\rm{NN}}=2.76$ TeV relative to the collision symmetry plane defined by the spectator nucleons. A negative slope of the rapidity-odd directed flow component with approximately 3 times smaller magnitude than found at the highest RHIC energy is observed. This suggests a smaller longitudinal tilt of the initial system and disfavors the strong fireball rotation predicted for the LHC energies. The rapidity-even directed flow component is measured for the first time with spectators and found to be independent of pseudorapidity with a sign change at transverse momenta $p_{\mathrm{T}}$ between $1.2$ and $1.7$ GeV/$c$. Combined with the observation of a vanishing rapidity-even $p_{\mathrm{T}}$ shift along the spectator deflection this is strong evidence for dipole-like initial density fluctuations in the overlap zone of the nuclei. Similar trends in the rapidity-even directed flow and the estimate from two-particle correlations at mid-rapidity, which is larger by about a factor of 40, indicate a weak correlation between fluctuating participant and spectator symmetry planes. These observations open new possibilities for investigation of the initial conditions in heavy-ion collisions with spectator nucleons.

17 pages, 4 captioned figures, authors from page 12, published version, figures at http://aliceinfo.cern.ch/ArtSubmission/node/463

References in corpus (12)

• The Chiral Magnetic Effect
• Triangularity and Dipole Asymmetry in Heavy Ion Collisions
• Centrality determination of Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}}}$ = 2.76 TeV with ALICE
• Suppression of elliptic flow in a minimally viscous quark-gluon plasma
• Charge separation relative to the reaction plane in Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}}}=2.76$ TeV
• Directed flow in ultrarelativistic heavy-ion collisions
• Third Harmonic Flow of Charged Particles in Au+Au Collisions at sqrtsNN = 200 GeV
• System-size independence of directed flow at the Relativistic Heavy-Ion Collider
• Effects of non-uniform acceptance in anisotropic flow measurement
• Directed flow at mid-rapidity in event-by-event hydrodynamics
• Beam Fragmentation in Heavy Ion Collisions with Realistically Correlated Nuclear Configurations
• Anisotropic flow in Pb+Pb collisions at LHC from the quark gluon string model with parton rearrangement

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