https://doi.org/10.1140/epja/s10050-025-01484-x
Regular Article - Theoretical Physics
Neutrinoless 
-decay in DCEQTDA
1
School of Engineering and Sciences, São Paulo State University (UNESP), 19274-000, Rosana, SP, Brazil
2
Departamento de Ciências Exatas, Universidade Estadual de Santa Cruz, Campus Soane Nazaré de Andrade, Rod. Jorge Amado Km 16, 45662-900, Ilhéus, BA, Brazil
3
Centro de Ciências Exatas e Tecnológicas, Universidade Federal do Recôncavo da Bahia, 44380-000, Cruz das Almas, BA, Brazil
4
Departamento de Física, Universidad Nacional de La Plata, C.C. 67, 1900, La Plata, Argentina
5
Instituto de Física La Plata, CONICET, 1900, La Plata, Argentina
Received:
21
April
2024
Accepted:
6
January
2025
Published online:
18
February
2025
We have recently developed a nuclear model, which is a natural extension of the pn-QRPA model, specially designed to describe double charge exchange (DCE) processes generated by two-body DCE transition operators. It is based on the Quasiparticle Tamm–Dancoff approximation (QTDA) for pn and 2p2n excitations in intermediate and final nuclei, respectively, and will be called DCEQTDA. As such, this model, having the same number of free parameters as the pn-QRPA, also brings into play the excitations of four quasiparticles to build up the final nuclear states, which are then used to evaluate the nuclear matrix elements (NMEs) for all 
and 
final states, including resonances, and not just for the ground state as in pn-QRPA. In addition, it allows us to evaluate: (a) the values of 
, (b) the excitation energies in final nuclei, and (c) the DCE sum rules, which are fulfilled in the DCEQTDA. So far, this model has been used mainly to calculate double beta decays with the emission of two neutrinos (
-decay). Here, we extend it to the study of these processes when no neutrinos are emitted (
-decay), evaluating them in a series of nuclei, but paying special to: (i) 
Se, which have been measured recently in the GERDA and MAJORANA experiments, and (ii) 
Te, for which the first direct observation of the double electron capture 
has been performed with the XENON1T dark matter detector. We obtain good agreement with the data for both the ground state and the excited states. The validity of the DCEQTDA model is checked by comparing the calculation with the experimental data for the 
NMEs, and for the , in a series of nuclei.
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© The Author(s), under exclusive licence to Società Italiana di Fisica and Springer-Verlag GmbH Germany, part of Springer Nature 2025
Springer Nature or its licensor (e.g. a society or other partner) holds exclusive rights to this article under a publishing agreement with the author(s) or other rightsholder(s); author self-archiving of the accepted manuscript version of this article is solely governed by the terms of such publishing agreement and applicable law.
