Anisotropic flow fluctuations in hydro-inspired freeze-out model for relativistic heavy ion collisions

L V Bravina,I P Lokhtin,E N Nazarova,E S Fotina,L V Malinina,E E Zabrodin,V L Korotkikh,A M Snigirev,S V Petrushanko

doi:10.1140/epjc/s10052-015-3815-9

Abstract

The LHC data on event-by-event harmonic flow coefficients measured in PbPb collisions at center-of-mass energy 2.76 TeV per nucleon pair are analyzed and interpreted within the HYDJET++ model. To compare the model results with the experimental data the unfolding procedure is employed. The essentially dynamical origin of the flow fluctuations in hydro-inspired freeze-out approach has been established. It is shown that the simple modification of the model via introducing the distribution over spatial anisotropy parameters permits HYDJET++ to reproduce both elliptic and triangular flow fluctuations and related to it eccentricity fluctuations of the initial state at the LHC energy.

Highlights

Azimuthal anisotropy of multi-particle production in relativistic heavy ion collisions is a powerful probe of collective properties of sub-nuclear matter created at extremely high densities and temperatures
At the LHC, a number of interesting measurements involving momentum and centrality dependencies of second- an√d higher-order harmonic coefficients in PbPb collisions at sNN = 2.76 TeV have been done by ALICE [7,8,9], ATLAS [10,11,12,13,14,15] and CMS [16,17,18,19,20] Collaborations
Other important observations are the azimuthal anisotropy of jet [21] and charmed meson [22,23] yields in PbPb collisions, and elliptic v2 and triangular v3 flow of inclusive [24,25,26] and identified [27] hadrons in pPb collisions

Summary

Introduction

Azimuthal anisotropy of multi-particle production in relativistic heavy ion collisions is a powerful probe of collective properties of sub-nuclear matter created at extremely high densities and temperatures (see, e.g., recent reviews [1,2] and references therein). To get some notion for the inherent model fluctuations, we start with HYDJET++ simulations for the simplest case of central PbPb collisions (b = 0) in which all azimuthal anisotropy parameters (b), δ(b), and 3(b) are equal to zero. The simplest modification for this purpose is to introduce EbyE Gaussian smearing of the spatial anisotropy parameters (b) and 3(b) with the widths proportional to its “unsmeared” values The coefficients of this proportionality are independent on event centrality and tuned to fit the data. Both model versions, with and without the smearing, are employed for the extraction of the flow fluctuations and comparison with the available experimental data

Unfolding procedure for flow fluctuations analysis

Findings

Conclusions