Improved short-range correlations and 0nbb nuclear matrix elements of 76Ge and 82Se

TL;DR

This paper improves calculations of nuclear matrix elements for neutrinoless double beta decay in 76Ge and 82Se by using advanced correlation methods, significantly impacting experimental detectability.

Contribution

It introduces the use of the unitary correlation operator method (UCOM) for short-range correlations, replacing Jastrow functions, leading to larger matrix element estimates.

Findings

UCOM increases the magnitude of matrix elements compared to Jastrow.

Enhanced matrix elements suggest better prospects for detecting 0νββ decay.

Results impact the interpretation of experimental sensitivities.

Abstract

We calculate the nuclear matrix elements of the neutrinoless double beta ($0\nu\beta\beta$) decays of $^{76}$Ge and $^{82}$Se for the light-neutrino exchange mechanism. The nuclear wave functions are obtained by using realistic two-body forces within the proton-neutron quasiparticle random-phase approximation (pnQRPA). We include the effects that come from the finite size of a nucleon, from the higher-order terms of nucleonic weak currents, and from the nucleon-nucleon short-range correlations. Most importantly, we improve on the presently available calculations by replacing the rudimentary Jastrow short-range correlations by the more advanced unitary correlation operator method (UCOM). The UCOM corrected matrix elements turn out to be notably larger in magnitude than the Jastrow corrected ones. This has drastic consequences for the detectability of $0\nu\beta\beta$ decay in the present and future double beta experiments.