Breaking of factorization of two-particle correlations in hydrodynamics

Abstract

The system formed in ultrarelativistic heavy-ion collisions behaves as a nearly-perfect fluid. This collective behavior is probed experimentally by two-particle azimuthal correlations, which are typically averaged over the properties of one particle in each pair. In this Letter, we argue that much additional information is contained in the detailed structure of the correlation. In particular, the correlation matrix exhibits an approximate factorization in transverse momentum, which is taken as a strong evidence for the hydrodynamic picture, while deviations from the factorized form are taken as a signal of intrinsic, "nonflow" correlations. We show that hydrodynamics in fact predicts factorization breaking as a natural consequence of initial state fluctuations and averaging over events. We derive the general inequality relations that hold if flow dominates, and which are saturated if the matrix factorizes. For transverse momenta up to 5 GeV, these inequalities are satisfied in data, but not saturated. We find at least as large factorization breaking in event-by-event ideal hydrodynamic calculations as in data, and argue that this phenomenon opens a new window on the study of initial fluctuations.

5 pages, 2 figures. Minor revision

References in corpus (37)

• Viscosity Information from Relativistic Nuclear Collisions: How Perfect is the Fluid Observed at RHIC?
• Elliptic flow of charged particles in Pb-Pb collisions at 2.76 TeV
• Elliptic and triangular flow in event-by-event (3+1)D viscous hydrodynamics
• Elliptic Flow of Identified Hadrons in Au+Au Collisions at sqrt(s_NN) = 200 GeV
• Elliptic flow in Au+Au collisions at sqrt(s_NN) = 130 GeV
• Measurement of the azimuthal anisotropy for charged particle production in sqrt(s_NN) = 2.76 TeV lead-lead collisions with the ATLAS detector
• Parton-Based Gribov-Regge Theory
• System Size, Energy, Pseudorapidity, and Centrality Dependence of Elliptic Flow
• Mapping the hydrodynamic response to the initial geometry in heavy-ion collisions
• Centrality dependence of dihadron correlations and azimuthal anisotropy harmonics in PbPb collisions at sqrt(s[NN]) = 2.76 TeV
• Harmonic decomposition of two-particle angular correlations in Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}}}$ = 2.76 TeV
• Effects of initial flow velocity fluctuation in event-by-event (3+1)D hydrodynamics
• Topology studies of hydrodynamics using two particle correlation analysis
• Centrality and pseudorapidity dependence of elliptic flow for charged hadrons in Au+Au collisions at sqrt(sNN) = 200 GeV
• Radiative energy loss and v2 spectra for viscous hydrodynamics
• Relativistic Theory of Hydrodynamic Fluctuations with Applications to Heavy Ion Collisions
• Long range two-particle rapidity correlations in A+A collisions from high energy QCD evolution
• Topics on Hydrodynamic Model of Nucleus-Nucleus Collisions
• Torqued fireballs in relativistic heavy-ion collisions
• The Fate of the Initial State Fluctuations in Heavy Ion Collisions. II The Fluctuations and Sounds
• Importance of Granular Structure in the Initial Conditions for the Elliptic Flow
• Collective flow and long-range correlations in relativistic heavy ion collisions
• Anisotropic flow in event-by-event ideal hydrodynamic simulations of sqrt(s_{NN})=200 GeV Au+Au collisions
• Super-horizon fluctuations and acoustic oscillations in relativistic heavy-ion collisions
• Non-flow correlations and elliptic flow fluctuations in gold-gold collisions at sqrt(s_NN)= 200 GeV
• The Fate of the Initial State Fluctuations in Heavy Ion Collisions. III The Second Act of Hydrodynamics
• Flow fluctuations and long-range correlations: elliptic flow and beyond
• Implications of space-momentum correlations and geometric fluctuations in heavy-ion collisions
• Directed flow at mid-rapidity in event-by-event hydrodynamics
• Directed flow at midrapidity in sqrt(s_NN)=2.76 TeV Pb+Pb collisions
• Effects of HBT correlations on flow measurements
• Measurement of elliptic and higher order flow from ATLAS experiment at the LHC
• Identified particles in pp and Pb-Pb collisions at LHC energies with the ALICE detector
• Temporal evolution of tubular initial conditions and their influence on two-particle correlations in relativistic nuclear collisions
• Effects of initial state fluctuations in the final state elliptic flow measurements using the NeXSPheRIO model
• Nonflow "factorization" and a novel method to disentangle anisotropic flow and nonflow
• Triggered di-hadron correlations in Pb--Pb collisions from the ALICE experiment

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