Centrality-dependent analysis of hadrons and light nuclei for phase transition insights in intermediate-energy Au-Au collisions

This study investigates various hadron species and light nuclei in Au-Au collisions at $\sqrt{s_{NN}}$ =27 and 39 GeV. The analytical approach employs a two-component standard distribution to extract important parameters, including effective temperature (T), mean transverse momentum ($⟨$p${}_T⟩$), initial temperature (T${}_i$), and multiplicity parameter (N${}_0$). The average kinetic freeze-out temperature ($⟨$T${}_0⟩$) and transverse flow velocity ($⟨$β${}_T⟩$) are determined using an alternative method. Results indicate that the first indication of the phase transition, characterized by a plateau-type region in temperature and/or other parameters, appears in the first three centralities at 27 GeV and then in the first four centralities at 39 GeV for all hadron species. This suggests that with increasing the collision energies, the interval of collision centrality for the potential onset of the phase transition shifts toward the periphery. The parameters, except the N${}_0$, show a slight increase with collision energy, maintaining the same values at specific centralities linked to the phase transition. This supports the transition from hadronic matter to QCD matter. Furthermore, various parameters exhibit an incline or decline nature with collision energy (centrality), and they increase corresponding to the mass of produced particles, confirming a multiple freeze-out scenario. The inequality $⟨$T${}_i⟩$ >$⟨$T$⟩$ >$⟨$T${}_0⟩$ is verified, consistent with the time evolution of the QGP droplet. The analyzed value of $⟨$T${}_0⟩$ for centrality bins responsible for the phase transition is 140 MeV, very close to the QCD predicted QGP's critical temperature range.