Abstract
Benchmark comparisons between many-body methods are performed to assess the ingredients necessary for an accurate calculation of neutrinoless double beta decay matrix elements. Shell model and variational Monte Carlo (VMC) calculations are carried out for A=10 and 12 nuclei. Different variational wavefunctions are used to evaluate the uncertainties in the ab initio calculations, finding fairly small differences between the VMC double beta decay matrix elements. For shell model calculations, the role of model space truncation, radial wavefunction choices, and short-range correlation are investigated and all found to be important. Based on the detailed comparisons between the VMC and shell model approaches, we conclude that accurate descriptions of neutrinoless double beta decay matrix elements require a proper treatment of both long-range and short-range correlations.
Highlights
Neutrinoless double beta decay (0νββ) is a process in which two neutrons in a nucleus decay into two protons, with the emission of two electrons and no neutrinos, violating lepton number (L) by two units
The nuclear matrix elements of 48Ca have been calculated using the shell model [15,16,17,18], energy density functionals [19], the quasiparticle random-phase approximation (QRPA) [20], and the interacting boson model (IBM) [21], leading to results that differ by a factor of two or three
We concentrate on nuclei of mass 10 and 12, and we examine the role played by these different nuclear structure inputs in determining the predicted 0νββ nuclear matrix elements (NMEs)
Summary
Neutrinoless double beta decay (0νββ) is a process in which two neutrons in a nucleus decay into two protons, with the emission of two electrons and no neutrinos, violating lepton number (L) by two units. Isotopes of experimental interest for 0νββ searches, e.g. 48Ca, 76Ge, 82Se, 124Sn, 128Te, 130Te and 136Xe, are medium and heavy open-shell nuclei with very complex nuclear structure. For these nuclei, one is forced by current computational limitations to utilize approximate methods to solve the nuclear many-body problem, and to work in a truncated model spaces where correlations and many-body terms in both the nuclear interactions and currents may be insufficient or neglected. The goal of the present work is to benchmark shell model calculations of the relevant 0νββ NMEs in light nuclei to the aforementioned VMC results.
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