# Rapidity scan with multistage hydrodynamic and statistical thermal models

## TL;DR

This paper calibrates a multistage hydrodynamic and statistical thermal model to experimental data from heavy-ion collisions, studying the thermodynamics and phase diagram of nuclear matter across rapidities, and proposing an improved thermal model at low energies.

## Contribution

It introduces a hybrid framework combining hydrodynamics and thermal models to analyze rapidity-dependent data and proposes a new thermal model incorporating flow effects for low-energy collisions.

## Key findings

- Significant uncertainties in thermal model parameters away from midrapidity.
- Successful calibration of the hybrid model to experimental rapidity distributions.
- Proposal of a thermal model with flow effects for low-energy nuclear matter.

## Abstract

We calibrate a (3+1)-dimensional multistage hybrid framework using the measured pseudo-rapidity distribution of charged particles and rapidity distribution of net protons for central Au+Au collisions at $\sqrt{s_{\rm NN}}=7.7,\,19.6,\,62.4,\,200$ GeV. We then study the thermodynamic properties of the nuclear matter along the beam direction, and the phase diagram regions probed by the hadronization process near the chemical freeze-out. Using the rapidity-dependent thermal yields of identified particles with full rapidity coverage from the hybrid framework, we apply different scenarios of the statistical thermal model to extract the thermodynamic parameters at the freeze-out, with the known system properties from the hybrid model as a closure test. We find significant theoretical uncertainties in the thermal models when applied to regions away from midrapidity. We also propose a thermal model inspired by the hybrid approach that includes thermal smearing and longitudinal flow for the nuclear matter created at low beam energies.