Abstract
We report on a study of the Gamow-Teller matrix element contributing to decay with similarity renormalization group (SRG) versions of momentum- and configuration-space two-nucleon interactions. These interactions are derived from two different formulations of chiral effective field theory (—without and with the explicit inclusion of isobars. We consider evolution parameters in the range between 1.2 and 2.0 and, for the -less case, also the unevolved (bare) interaction. The axial current contains one- and two-body terms, consistently derived at tree level (no loops) in the two distinct formulations we have adopted here. The and ground-state wave functions are obtained from hyperspherical-harmonics (HH) solutions of the nuclear many-body problem. In systems, the HH method is limited at present to treat only two-body interactions and non-SRG evolved currents. Our results exhibit a significant dependence on of the contributions associated with two-body currents, suggesting that a consistent SRG-evolution of these is needed in order to obtain reliable estimates. We also show that the contributions from one-pion-exchange currents depend strongly on the model (chiral) interactions and on the momentum- or configuration-space cutoffs used to regularize them. These results might prove helpful in clarifying the origin of the sign difference recently found in no-core-shell-model and quantum Monte Carlo calculations of the Gamow-Teller matrix element.
- Received 15 June 2021
- Accepted 25 August 2021
DOI:https://doi.org/10.1103/PhysRevC.104.035501
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