Rapidity decorrelation caused by hydrodynamic fluctuations and initial longitudinal fluctuations

Factorisation breaking of the anisotropic flow coefficients is actively studied to understand the longitudinal dynamics of the quark-gluon plasma produced in high-energy nuclear collisions. Yet no hydrodynamic models have successfully described the centrality dependence of the factorisation breaking in various collisions systems. In this study, we reproduce the centrality dependence of the factorisation ratio in Pb+Pb collisions at LHC by constructing an integrated dynamical model with hydrodynamic fluctuations and initial longitudinal fluctuations. Hydrodynamic fluctuations are thermal fluctuations arising during the hydrodynamic stage of the high-energy nuclear collisions. We include the hydrodynamic fluctuations obeying the fluctuation-dissipation theorem. For the initial longitudinal fluctuations, we run PYTHIA for each binary p+p collision, scale the distribution of the produced particles by the number of participants and assume the distribution to be the entropy density distribution. We switch on and off the hydrodynamic fluctuations to investigate the effects on the longitudinal rapidity decorrelation.