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arXiv · 1510.06824

Testing the importance of collective correlations in neutrinoless $ββ$ decay

J. Menéndez·N. Hinohara·J. Engel·G. Martínez-Pinedo·T. R. Rodríguez
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Abstract

We investigate the extent to which theories of collective motion can capture the physics that determines the nuclear matrix elements governing neutrinoless double-beta decay. To that end we calculate the matrix elements for a series of isotopes in the full $pf$ shell, omitting no spin-orbit partners. With the inclusion of isoscalar pairing, a separable collective Hamiltonian that is derived from the shell model effective interaction reproduces the full shell-model matrix elements with good accuracy. A version of the generator coordinate method that includes the isoscalar pairing amplitude as a coordinate also reproduces the shell model results well, an encouraging result for theories of collective motion, which can include more single-particle orbitals than the shell model. We briefly examine heavier nuclei relevant for experimental double-beta decay searches, in which shell-model calculations with all spin-orbit partners are not feasible; our estimates suggest that isoscalar pairing also plays a significant role in these nuclei, though one we are less able to quantify precisely.

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J. Menéndez, N. Hinohara, J. Engel, G. Martínez-Pinedo, T. R. Rodríguez. 2016-01-12. Testing the importance of collective correlations in neutrinoless $ββ$ decay. https://doi.org/10.1103/physrevc.93.014305

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