Neutrinoless $ββ$ decay nuclear matrix elements complete up to N$^2$LO in heavy nuclei
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arXiv
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2024
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| author | Castillo, Daniel Jokiniemi, Lotta Soriano, Pablo Menéndez, Javier |
| author_facet | Castillo, Daniel Jokiniemi, Lotta Soriano, Pablo Menéndez, Javier |
| contents | We evaluate all nuclear matrix elements (NMEs) up to next-to-next-to leading order (N$^2$LO) in chiral effective field theory ($χ$EFT) for the neutrinoless double-beta ($0νββ$) decay of the nuclei most relevant for experiments, including $^{76}$Ge, $^{100}$Mo, and $^{136}$Xe. We use the proton-neutron quasiparticle random-phase approximation (pnQRPA) and the nuclear shell model to calculate the N$^2$LO NMEs from very low-momentum (ultrasoft) neutrinos and from loop diagrams usually neglected in $0νββ$ studies. Our results indicate that the overall N$^2$LO contribution is centered around $-(5$-$10)\%$ for the shell model and $+(10$-$15)\%$ for the pnQRPA, with sizable uncertainties due to the scale dependence of the ultrasoft NMEs and the short-range nature of the loop NMEs. The sign discrepancy between many-body methods is common to all studied nuclei and points to the different behaviour of the intermediate states of the $0νββ$ decay. Within uncertainties, our results for the ultrasoft NME are of similar size as contributions usually referred to as ``beyond the closure approximation''. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2408_03373 |
| institution | arXiv |
| publishDate | 2024 |
| record_format | arxiv |
| spellingShingle | Neutrinoless $ββ$ decay nuclear matrix elements complete up to N$^2$LO in heavy nuclei Castillo, Daniel Jokiniemi, Lotta Soriano, Pablo Menéndez, Javier Nuclear Theory High Energy Physics - Experiment High Energy Physics - Phenomenology Nuclear Experiment We evaluate all nuclear matrix elements (NMEs) up to next-to-next-to leading order (N$^2$LO) in chiral effective field theory ($χ$EFT) for the neutrinoless double-beta ($0νββ$) decay of the nuclei most relevant for experiments, including $^{76}$Ge, $^{100}$Mo, and $^{136}$Xe. We use the proton-neutron quasiparticle random-phase approximation (pnQRPA) and the nuclear shell model to calculate the N$^2$LO NMEs from very low-momentum (ultrasoft) neutrinos and from loop diagrams usually neglected in $0νββ$ studies. Our results indicate that the overall N$^2$LO contribution is centered around $-(5$-$10)\%$ for the shell model and $+(10$-$15)\%$ for the pnQRPA, with sizable uncertainties due to the scale dependence of the ultrasoft NMEs and the short-range nature of the loop NMEs. The sign discrepancy between many-body methods is common to all studied nuclei and points to the different behaviour of the intermediate states of the $0νββ$ decay. Within uncertainties, our results for the ultrasoft NME are of similar size as contributions usually referred to as ``beyond the closure approximation''. |
| title | Neutrinoless $ββ$ decay nuclear matrix elements complete up to N$^2$LO in heavy nuclei |
| topic | Nuclear Theory High Energy Physics - Experiment High Energy Physics - Phenomenology Nuclear Experiment |
| url | https://arxiv.org/abs/2408.03373 |