Bayesian reconstruction of anisotropic flow fluctuations at fixed impact parameter

Abstract

The cumulants of the distribution of anisotropic flow are measured accurately in Pb+Pb collisions at the LHC as a function of centrality classifiers (charged multiplicity and/or transverse energy). Using Bayesian inference, we reconstruct from these measurements the probability distribution of anisotropic flow in the ``theorists' frame'' where the impact parameter has a fixed magnitude and orientation, up to $\sim 70\%$ centrality. The variation of flow fluctuations with impact parameter displays direct evidence of viscous damping, which is larger for higher Fourier harmonics, in line with expectations from hydrodynamics. We use intensive measures of non-Gaussian flow fluctuations, which have reduced dependence on centrality. We infer from ATLAS data the magnitude of these intensive non-Gaussianities in each Fourier harmonic. They provide data-driven estimates of response coefficients to initial anisotropies, without resorting to any specific microscopic model of initial conditions. These estimates agree with viscous hydrodynamic calculations.

16 pages, 8 figures

References in corpus (12)

• Glauber Modeling in High Energy Nuclear Collisions
• Viscosity Information from Relativistic Nuclear Collisions: How Perfect is the Fluid Observed at RHIC?
• Elliptic and triangular flow in event-by-event (3+1)D viscous hydrodynamics
• Alternative ansatz to wounded nucleon and binary collision scaling in high-energy nuclear collisions
• Triangularity and Dipole Asymmetry in Heavy Ion Collisions
• Elliptic flow in the Gaussian model of eccentricity fluctuations
• Momentum spectra, anisotropic flow, and ideal fluids
• $v_4$, $v_5$, $v_6$, $v_7$: nonlinear hydrodynamic response versus LHC data
• Skewness of elliptic flow fluctuations
• Eccentricity distributions in nucleus-nucleus collisions
• Continuous description of fluctuating eccentricities
• The fluctuations of quadrangular flow