Time-dependent random phase approximation for particle-number fluctuations and correlations in deep-inelastic collisions of $^{144}$Sm+$^{144}$Sm and $^{154}$Sm+$^{154}$Sm (2504.09436v1)

Abstract: The fluctuation-dissipation mechanism underlying non-equilibrium transport in low-energy heavy-ion reactions remains unclear. Although the time-dependent Hartree-Fock (TDHF) method provides a reasonable description of average reaction outcomes and one-body dissipation, it is known to significantly underestimate fluctuations of observables. The purpose of this work is to investigate deep-inelastic collisions of 144Sm+144Sm and 154Sm+154Sm with microscopic mean-field approaches and to show a predominant role of one-body dissipation as well as one-body fluctuations and correlation in low-energy heavy-ion reactions. Three dimensional TDHF calculations are carried out for 144Sm+144Sm at Ecm=500 MeV and 154Sm+154Sm at Ecm=485 MeV for a range of impact parameters with Skyrme SLy5 energy density functional. Backward time evolutions are performed as well to evaluate fluctuations and correlation in nucleon numbers within time-dependent random phase approximation (TDRPA). With TDRPA we calculate mass- and charge-number fluctuations, as well as the correlation between neutron and proton transfers, for each impact parameter. We demonstrate that TDRPA quantitatively reproduces the experimental \sigma_{AA}^2-TKEL distributions, whereas it systematically underestimates the charge fluctuation, \sigma_{ZZ}. The double-differential cross sections of reaction products are calculated, showing good agreement with the experimental data. We confirm a long-thought characteristic property that the closed-shell structure limits nucleon transfer at small energy losses, based on our microscopic TDHF and TDRPA calculations.