Speaker
Description
We explore the impact of the equation of state (EoS) on heavy-ion collision observables using a Chiral Mean Field (CMF) framework constrained by astrophysical and lattice-QCD inputs. By varying the relative vector and scalar–vector couplings of $\Delta$ resonances and the scalar $\sigma$ field with respect to nucleons, we identify a family of EoS that simultaneously reproduce neutron stars with masses above two solar masses and exhibit a first-order phase transition around 2 times the nuclear saturation density. These EoS also reproduce the QCD trace anomaly at finite temperature. We implement both, the default CMF EoS and the modified EoS featuring a phase transition into the UrQMD transport model and study Au+Au collisions at beam energies of 0.5–3 GeV, the GSI/FAIR energy range of the HADES and CBM experiments. We analyze rapidity and transverse-momentum distributions for protons, $\pi^+, \pi^-, K^+$, and deuterons, compute directed flow ($v_1$) and its slope near midrapidity, and evaluate the $K^+/\pi^+$ ratio. Clear differences emerge between the results obtained with the default CMF EoS, the modified EoS, and the cascade mode, particularly in pions $v_1$ slopes and strangeness production. These findings demonstrate the sensitivity of low energy heavy ion observables to the nuclear EoS and highlight potential experimental signatures of a hadron–quark phase transition.