Coupling charge-exchange vibrations to nucleons in a relativistic framework: effect on Gamow-Teller transitions and beta-decay half-lives
Abstract
The nuclear response theory for isospin-transfer modes in the relativistic particle-vibration coupling framework is extended to include coupling of single nucleons to isospin-flip (charge-exchange) phonons, in addition to the usual neutral vibrations. This new coupling introduces dynamical pion and rho-meson exchange, beyond the Hartree-Fock approximation, up to infinite order. We investigate the impact of this new mechanism on the Gamow-Teller response of a few doubly-magic neutron-rich nuclei, namely 48Ca, 78Ni, 132Sn and 208Pb. It is found that the coupling to isospin-flip vibrations can have a non negligible impact on the strength distribution and quenching of the giant resonance, globally improving the agreement with the experimental data. The corresponding beta-decay half-lives of 78Ni and 132Sn are also calculated, and found to be decreased by a factor 2 by the inclusion of the new phonons.