Effects of hydrodynamic fluctuations in heavy ion collisions*

Fluctuations have been playing an important role in understanding observables in high-energy nuclear collisions. For example, event-by-event initial fluctuations of transverse profiles are discussed to understand higher harmonics of azimuthal angle distributions. Recently, to understand the rapidity decorrelation, initial fluctuations in longitudinal direction and thermal fluctuations during hydrodynamic evolution of the QGP fluids are studied. In this presentation, we focus on the effect of thermal fluctuations on rapidity decorrelation.

We employ an integrated dynamical model which combines full three-dimensional relativistic hydrodynamics with a Monte-Carlo version of the Glauber model for event-by-event initialization and the hadronic cascade model in the late rescattering stage. By using this model, we first tune initial parameters and transport coefficients to reproduce pseudorapidity distribution, and centrality dependence of integrated elliptic flow coefficients in Pb+Pb collisions at the LHC energy. We next analyze the n-th order factorization ratios, which quantify rapidity decorrelation. By switching on and off hydrodynamic fluctuations in the hydrodynamic stage, we see how hydrodynamic fluctuations affect rapidity decorrelation.