{"record":{"author":{"account_ref":null,"orcid":null},"builds_on":[],"content_schema":"pubphys.content.revision/1","content_sha256":"2dd2603609888fe4c991a096ed095b49a231ad141247de8e61ce8ed32fd6d38c","created":"2026-10-03T07:18:07Z","files":[],"origin":{"assisted_by":[],"kind":"seed"},"parents":["5475cf5dc5b1a72283d26dc95dc6e00d7ea4e00096a7c6492e409a1816eeb011"],"salt":"df2051c42f550ebb235215b91862ba66da5fbed973bd5c06521c2f783839f904","schema":"pubphys.record/2","site":"pubphys.com","target":null,"type":"revision"},"content":{"answer_type":"value","assisted_by":[],"external_id":"nuc.double-beta-nme.contact-term-coupling","kind":"well-posed","literature_status":"partially-resolved","n":"1","parents":[],"plain":"Effective field theory showed in 2018 that the leading neutrinoless double beta decay operator needs a short-range two-nucleon term whose strength is not fixed by symmetry. Its value changes the matrix elements by tens of percent.","posed_since":"2018","precise":"Determine the leading-order low-energy constant $g_{\\nu}^{NN}$ of the $\\mathrm{nn} \\to \\mathrm{pp}\\,\\mathrm{e}\\,\\mathrm{e}$ contact operator in chiral EFT (Cirigliano et al., PRL 120, 202001, 2018), from a lattice QCD calculation of the $\\mathrm{nn} \\to \\mathrm{pp}$ amplitude or from the dispersive estimate (Cirigliano et al., PRL 126, 172002, 2021). Answer: $g_{\\nu}^{NN}$ with 20 percent uncertainty in a stated regulator scheme, and its effect on $M^{0\\nu}$ for 76Ge and 136Xe.","problem_ref":null,"references":"","settled_by":"A lattice QCD calculation of the two-nucleon $\\mathrm{nn} \\to \\mathrm{pp}\\, e\\, e$ amplitude at physical quark masses matched to chiral EFT.","status_note":"The 2021 dispersive estimate fixed $g_{\\nu}^{\\mathrm{NN}}$ to about 30 percent and ab initio studies found the term changes $M^{0\\nu}$ by tens of percent; no physical-point lattice QCD determination existed as of 2026.","title":"Short-range contact coupling in neutrinoless double beta decay","topic_ref":"4f4c723b8298474d47f16416d8eb15f7bae4b6a7810849f79c8cbc3d0064c494"},"attested":{"attestation":{"batch":null,"client_id":null,"id_token_sha256":null,"kind":"platform"},"record_hash":"73df88baa2b5b445a99e34d27bb37414d11a8433e4878576f44817129b4d039f","schema":"pubphys.attested/1"},"envelope":{"attested_hash":"6086e0ac7ac89fd673b2d51c81c29be6bd268fad1438999cc9593f8c4b1ded22","platform_signature":{"key_id":"c6afc19b31429869751f06879c75cd64ea92654423d15b44be775bf1310a60da","sig":"gQU2xG7SAKmx2Tz1VDr7l3ZBq1GTQSgkVgYdATAwgI2iK-x-41Z6kuOzCQFVxcFo7zJ2QZ4nmLtCdvtgM0PIDw"},"schema":"pubphys.envelope/1"},"record_hash":"73df88baa2b5b445a99e34d27bb37414d11a8433e4878576f44817129b4d039f","leaf_index":1736}