Rapidity scan with multistage hydrodynamic and statistical thermal models

Abstract

We calibrate a ($3+1$)-dimensional multistage hybrid framework using the measured pseudorapidity distribution of charged particles and rapidity distribution of net protons for central Au $+$ Au collisions at $\sqrt{{s}_{NN}}=7.7,\phantom{\rule{0.16em}{0ex}}19.6,\phantom{\rule{0.16em}{0ex}}62.4,\phantom{\rule{0.16em}{0ex}}200$ 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.