Symmetry breaking of Gamow-Teller and magnetic-dipole transitions and its restoration in calcium isotopes

Abstract

Nuclear magnetic-dipole (M1) and Gamow-Teller (GT) transitions provide insight into the spin-isospin properties of atomic nuclei. By considering them as unified spin-isospin transitions, the M1/GT transition strengths and excitation energies are subject to isospin symmetry. The excitation properties associated to the M1/GT symmetry need to be clarified within consistent theoretical approach. In this work, the relationship between the M1 and GT transitions in Ca isotopes is investigated in a unified framework based on the relativistic energy-density functional (REDF) with point-coupling interactions, using the relativistic quasi-particle random-phase approximation (RQRPA). It is shown that the isovector-pseudovector (IV-PV) residual interaction affects both transitions, and the symmetry of M1 and giant-GT transitions is disrupted by this interaction in closed-shell nuclei. In open-shell Ca isotopes, the proton-neutron pairing in the residual RQRPA interaction also plays a role in GT transitions. Due to the interplay between these interactions, the M1/GT symmetry can be restored especially in the ${}^{42}$Ca nucleus, i.e., the giant-GT strength can become comparable to that of the M1 mode in terms of the unified spin-isospin transitions by adjusting the PN-pairing strength to reproduce the experimental low-lying GT-excitation energies. The mirror symmetry of both M1 and GT transitions is also demonstrated for open-shell mirror partners, ${}^{42}$Ca and ${}^{42}$Ti. Further improvements are required to achieve simultaneous reproduction of M1 and GT-transition energies in the REDF framework.

1 Table, 8 Figures, accepted in Phys. Rev. C

References in corpus (17)

• Relativistic Continuum Hartree Bogoliubov Theory for Ground State Properties of Exotic Nuclei
• Theory of Core-Collapse Supernovae
• Exotic modes of excitation in atomic nuclei far from stability
• Relativistic Nuclear Energy Density Functionals: adjusting parameters to binding energies
• DIRHB -- a relativistic self-consistent mean-field framework for atomic nuclei
• Current Status of r-Process Nucleosynthesis
• A new Skyrme interaction with improved spin-isospin properties
• Optimizing the relativistic energy density functional with nuclear ground state and collective excitation properties
• The Gamow-Teller response within Skyrme random-phase approximation plus particle-vibration coupling
• Electron capture in stars
• Skyrme-Rpa Description of Spin-Flip M1 Giant Resonance
• Continuum particle-vibration coupling method in coordinate-space representation for finite nuclei
• Nuclear charge-exchange excitations based on relativistic density-dependent point-coupling model
• Low-energy M1 excitations in ${}^{208}$Pb and the spin channel of the Skyrme energy-density functional
• Spin-orbit interaction in relativistic nuclear structure models
• Landau Migdal Theory of Interacting Fermi Systems: A Framework for Effective Theories in Nuclear Structure Physics
• Finite-temperature linear response theory based on relativistic Hartree Bogoliubov model with point-coupling interaction

Cited by in corpus (1)

• Magnetic quadrupole transitions in the relativistic energy density functional theory