Generator-coordinate reference states for spectra and $0\ensuremath{\nu}\ensuremath{\beta}\ensuremath{\beta}$ decay in the in-medium similarity renormalization group

Generator-coordinate reference states for spectra and $0 ν β β$ decay in the in-medium similarity renormalization group

J. M. Yao, J. Engel, L. J. Wang, C. F. Jiao, and H. Hergert

Phys. Rev. C 98, 054311 – Published 16 November 2018

Abstract

We use a reference state based on symmetry-restored states from deformed mean-field or generator-coordinate-method (GCM) calculations in conjunction with the in-medium similarity-renormalization group (IMSRG) to compute spectra and matrix elements for neutrinoless double-beta ( $0 ν β β$ ) decay. Because the decay involves ground states from two nuclei, we use evolved operators from the IMSRG in one nucleus in a subsequent GCM calculation in the other. We benchmark the resulting IMSRG+GCM method against complete shell-model diagonalization for both the energies of low-lying states in ${}^{48}{Ca}$ and ${}^{48}{Ti}$ and the $0 ν β β$ matrix element for the decay of ${}^{48}{Ca}$ , all in a single valence shell. Our approach produces better spectra than either the IMSRG with a spherical-mean-field reference or GCM calculations with unevolved operators. For the $0 ν β β$ matrix element the improvement is slight.

Received 29 July 2018

DOI:https://doi.org/10.1103/PhysRevC.98.054311

Physics Subject Headings (PhySH)

Neutrinoless double beta decay Nuclear many-body theory Shell model

39 ≤ A ≤ 58

Nuclear Physics

Authors & Affiliations

J. M. Yao

Department of Physics and Astronomy, University of North Carolina, Chapel Hill, North Carolina 27516-3255, USA and FRIB/NSCL, Michigan State University, East Lansing, Michigan 48824, USA

J. Engel and L. J. Wang

Department of Physics and Astronomy, University of North Carolina, Chapel Hill, North Carolina 27516-3255, USA

C. F. Jiao

Department of Physics and Astronomy, University of North Carolina, Chapel Hill, North Carolina 27516-3255, USA and Department of Physics, San Diego State University, San Diego, California 92182-1233, USA

H. Hergert