Interferometry Radii at RHIC BES Energies within the integrated HydroKinetic Model

Abstract

This study presents a correlation femtoscopy analysis of relativistic heavy-ion collisions at RHIC Beam Energy Scan (BES) energies using the extended integrated HydroKinetic Model (iHKMe). The model combines initial conditions from UrQMD transport simulations, a gradual pre-equilibrium relaxation stage, viscous hydrodynamic evolution, and a hadronic cascade, providing a comprehensive description of the system's full dynamical evolution. Special emphasis is placed on the impact of extended nuclear overlap times and partial thermalization, which are characteristic of intermediate collision energies (sqrt(s_NN) = 7.7-39 GeV). The corresponding correlation femtoscopy scales, or interferometry (HBT) radii, are calculated across a range of collision energies and compared with experimental data to assess the sensitivity of femtoscopic observables to the equation of state (EoS). Two EoS scenarios are explored. The model demonstrates good agreement with experimental femtoscopy measurements, particularly at lower BES energies. These results enhance our understanding of the space-time structure of the particle-emitting source and provide valuable insight into the nature of the QCD phase transition in the intermediate energy regime.