Effects of a phase transition on two-pion interferometry in heavy ion collisions at■=2.4-7.7 GeV

作者：Pengcheng Li; Jan Steinheimer; Tom Reichert; Apiwit Kittiratpattana; Marcus Bleicher; Qingfeng Li^*

来源：Science China Physics,Mechanics & Astronomy, 2023, 66(03): 92-101.

Hanbury-Brown-Twiss(HBT) correlations for charged pions in central Au+Au collisions at■=2.4-7.7 GeV(corresponding to beam kinetic energies in the fixed target frame from Elab=1.23 to 30 GeV/nucleon) are calculated using the ultra-relativistic quantum molecular dynamics model with different equations of state(EoSs).The effects of a phase transition at high baryon densities are clearly observed in the explored HBT parameters.The results show that the available data on the HBT radii,RO/RS and RO2-RS2,in the investigated energy region favor a relatively stiff EoS at low beam energies,which then turns into a soft EoS at high collision energies consistent with astrophysical constraints on the high-density EoS of quantum chromodynamics(QCD).The specific effects of two different phase transition scenarios on RO/RS and RO2-RS2 are investigated.A phase transition with a significant softening of the EoS below four times the nuclear saturation density can be excluded using HBT data.Our results highlight that the pion’s RO/RS and RO2-RS2 are sensitive to the stiffness of the EoS and can be used to constrain and understand the QCD EoS in a high baryon density region.