{"record":{"author":{"account_ref":null,"orcid":null},"builds_on":[],"content_schema":"pubphys.content.revision/1","content_sha256":"9dc04878e66d6076ca8c192b104f8ee9ccdc1ec05a3c30ee8d2f1cfb404c5cbb","created":"2026-10-03T07:18:07Z","files":[],"origin":{"assisted_by":[],"kind":"seed"},"parents":["5475cf5dc5b1a72283d26dc95dc6e00d7ea4e00096a7c6492e409a1816eeb011"],"salt":"ba5e410ae94a68677f9f2762419f9d758cfd7cc637f9b25cfa8d383d905fa8ca","schema":"pubphys.record/2","site":"pubphys.com","target":null,"type":"revision"},"content":{"answer_type":"value","assisted_by":[],"external_id":"nuc.double-beta-nme.nme-key-isotopes","kind":"well-posed","literature_status":"open","n":"1","parents":[],"plain":"Different nuclear models give matrix elements differing by factors of two to three for the same nucleus. Pinning them down for the isotopes used in experiments is the central task.","posed_since":"","precise":"For light Majorana neutrino exchange, compute $M^{0\\nu}$ for 76Ge, 82Se, 100Mo, 130Te and 136Xe including long-range, short-range contact and two-body-current terms, with quantified uncertainty below 30 percent. Shell model, QRPA (quasiparticle random-phase approximation), energy density functional and ab initio (in-medium similarity renormalization group, coupled cluster) results span roughly a factor of 3. Answer: $M^{0\\nu}$ with uncertainties, validated on related observables (2nubb rates, double Gamow-Teller strengths, muon capture).","problem_ref":null,"references":"","settled_by":"Converged ab initio calculations with Bayesian uncertainty for 76Ge and 136Xe agreeing across at least two many-body methods.","status_note":"Ab initio calculations for 76Ge gave values at the low end of the model range (Belley et al., PRL 2021), and the first Bayesian uncertainty quantification for 76Ge gave $M^{0\\nu} = 2.60 (+1.28, -1.36)$ (Belley et al., PRL 132, 182502, 2024); agreement across many-body methods for 136Xe was not established as of 2026.","title":"Neutrinoless double beta matrix elements to 30 percent uncertainty","topic_ref":"4f4c723b8298474d47f16416d8eb15f7bae4b6a7810849f79c8cbc3d0064c494"},"attested":{"attestation":{"batch":null,"client_id":null,"id_token_sha256":null,"kind":"platform"},"record_hash":"2a1dd7accf1760ad22f528fae4979e263df27d45d49902b9c2768600e1be6217","schema":"pubphys.attested/1"},"envelope":{"attested_hash":"3772f6388221762ca2df2dc3bacec0a19d770a87374c55c212f3c30a12985b96","platform_signature":{"key_id":"c6afc19b31429869751f06879c75cd64ea92654423d15b44be775bf1310a60da","sig":"iK-qjg2Gr7P0h5qRpNj74LaEpzGFLcsJR9mfu4-NtrO51mgE0PycML87VzC_bryR_0_7KCQSL0JvYjK_q2KjDA"},"schema":"pubphys.envelope/1"},"record_hash":"2a1dd7accf1760ad22f528fae4979e263df27d45d49902b9c2768600e1be6217","leaf_index":1739}