Baseline predictions of elliptic flow and fluctuations at the RHIC Beam Energy Scan using response coefficients

TL;DR

This paper predicts elliptic flow and fluctuations at RHIC Beam Energy Scan energies using response coefficients, adapting hydrodynamic models for baryon-rich matter, and compares these predictions with preliminary STAR data.

Contribution

It provides baseline predictions for elliptic flow and fluctuations at low energies by extrapolating high-energy physics and discusses adaptations needed for baryon-rich matter.

Findings

Initial eccentricities are nearly identical across energies.

Flow predictions are based on linear+cubic response models.

Preliminary STAR results inform response coefficient implications.

Abstract

Currently the RHIC Beam Energy Scan is exploring a new region of the Quantum Chromodynamic phase diagram at large baryon densities that approaches nuclear astrophysics regimes. This provides an opportunity to study relativistic hydrodynamics in a regime where the net conserved charges of baryon number, strangeness, and electric charge play a role, which will significantly change the theoretical approach to simulating the baryon-dense Quark-Gluon Plasma. Here we detail many of the important changes needed to adapt both initial conditions and the medium to baryon-rich matter. Then, we make baseline predictions for the elliptical flow and fluctuations based on extrapolating the physics at LHC and top RHIC energies to support future analyses of where and how the new baryon-dense physics causes these extrapolations to break down. First we compare eccentricities across beam energies, exploring their underlying assumptions; we find the the extrapolated initial state is predicted to be nearly identical to that at AuAu $\sqrt{s_{NN}}=200$ GeV. Then the final flow harmonic predictions are based on linear+cubic response. We discuss preliminary STAR results in order to determine the implications that they have for linear+cubic response coefficients at the lowest beam energy of AuAu $\sqrt{s_{NN}}=7$ GeV.