Gamow-Teller Strength in ^{48}Ca and ^{78}Ni with the Charge-Exchange Subtracted Second Random-Phase Approximation

Area of Science:

• Nuclear Physics
• Quantum Many-Body Theory

Background:

• Accurate calculations of nuclear excitations are crucial for understanding nuclear structure and reactions.
• Previous models often required empirical quenching factors to match experimental data for Gamow-Teller transitions.

Purpose of the Study:

• To develop a self-consistent theoretical framework for charge-exchange processes.
• To investigate Gamow-Teller excitations and beta-decay rates in specific nuclei using this new method.

Main Methods:

• Implementation of a fully self-consistent subtracted second random-phase approximation.
• Application of Skyrme energy-density functionals.
• Study of Gamow-Teller excitations in Calcium-48 and Nickel-78.

Main Results:

• Calculated Gamow-Teller strength below 30 MeV is significantly reduced compared to other energy-density functional calculations.
• The results show improved agreement with experimental data for Calcium-48 and Nickel-78's beta-decay rate.
• The inclusion of two-particle-two-hole configurations naturally explains the observed spectral distributions.

Conclusions:

• The developed method provides a more accurate description of charge-exchange processes without ad-hoc parameters.
• The findings have implications for nuclear astrophysics and the study of neutrinoless double-beta decay.