Rapidity Correlation Structures from Causal Hydrodynamics

TL;DR

This paper investigates how second order causal hydrodynamics with stochastic noise can explain unexpected rapidity structures in two-particle transverse momentum fluctuations observed at RHIC, beyond what classical Navier-Stokes theory predicts.

Contribution

It introduces a causal hydrodynamics model with stochastic noise to explain novel rapidity correlation structures in heavy-ion collisions.

Findings

Classical Navier-Stokes explains rapidity broadening but not the additional structure.

Second order Israel-Stewart hydrodynamics with noise accounts for the observed structures.

Provides a new theoretical framework for understanding fluctuation structures in relativistic heavy-ion collisions.

Abstract

Viscous diffusion can broaden the rapidity dependence of two-particle transverse momentum fluctuations. Surprisingly, measurements at RHIC by the STAR collaboration demonstrate that this broadening is accompanied by the appearance of unanticipated structure in the rapidity distribution of these fluctuations in the most central collisions. Although a first order classical Navier-Stokes theory can roughly explain the rapidity broadening, it cannot explain the additional structure. We propose that the rapidity structure can be explained using the second order causal Israel-Stewart hydrodynamics with stochastic noise.