Roles of pairing dynamics in fusion enhancement or suppression in Sn124+Ca40,48 and Sn132+Ni58 reactions at sub-barrier energies

Abstract

Background: The absence of large fusion enhancement at sub-barrier energies was experimentally observed in the $^{132}\mathrm{Sn}+^{58}\mathrm{Ni}$ system even though the $^{132}\mathrm{Sn}+^{58}\mathrm{Ni}$ system has many positive $Q$-value neutron transfer channels, like the $^{124,132}\mathrm{Sn}+^{40}\mathrm{Ca}$ systems.Purpose: We elucidate the roles of pairing dynamics in the enhancement and absence of enhancement of fusion reactions at near- and sub-barrier energies, as the dynamical pairing correlations were found recently to play an important role.Method: The real space density-constrained time-dependent Hartree-Fock-Bogoliubov (rDC-TDHFB) method, proposed in Phys. Rev. C 105, 014613 (2022), is exploited to investigate $^{124}\mathrm{Sn}+^{40,48}\mathrm{Ca}$ and $^{132}\mathrm{Sn}+^{58}\mathrm{Ni}$ reactions at near- and sub-barrier energies.Results: The experimental data of $^{124}\mathrm{Sn}+^{40,48}\mathrm{Ca}$ and $^{132}\mathrm{Sn}+^{58}\mathrm{Ni}$ fusion cross sections at near- and sub-barrier energies were finely reproduced when the pairing correlations were self-consistently considered in the microscopic simulations of collision dynamics. Pairing dynamics significantly raises the barrier height and reduces the fusion cross sections. The suppressions of fusion reactions at sub-barrier energies, as observed in the $^{132}\mathrm{Sn}+^{58}\mathrm{Ni}$ reaction, are correlated with pairing energy sharing among projectilelike and targetlike subsystems in colliding nuclei, and also affect nucleon transfers.Conclusions: Pairing correlations were found to play an important role in fusion reactions, and a large pairing energy sharing is strongly favored in the reactions lacking large fusion enhancements.