{"record":{"author":{"account_ref":null,"orcid":null},"builds_on":[],"content_schema":"pubphys.content.revision/1","content_sha256":"422811f2f41870a923d1a7b68ebfcecd67299b24220cb3f9ba98f91fe28612e4","created":"2026-10-15T23:43:22Z","files":[],"origin":{"assisted_by":[],"kind":"seed"},"parents":["02ea08734e6f7503d0222ff513d71aa481eb674b5da50e563ee8a8a626fb168a","ce59fb6cd812fc05906d0c60a71c75ea22bc686bcf38e7c3ef7010834d98ee7b"],"salt":"83629b6ff59f858a009095068253a433103a041206167c138230c75b6cfbf500","schema":"pubphys.record/2","site":"pubphys.com","target":null,"type":"revision"},"content":{"answer_type":"value","assisted_by":[],"external_id":"hep.neutrino-mass.absolute-mass","kind":"well-posed","literature_status":"open","n":"2","parents":[],"plain":"Oscillations measure only differences of neutrino masses. The overall scale must come from precise $\\beta$ decay spectra or from how neutrinos affected the growth of cosmic structure.","posed_since":"","precise":"Determine $m_{\\mathrm{lightest}}$, or equivalently $m_{\\beta}=(\\sum\\left|U_{ei}\\right|^{2}m_i^{2})^{1/2}$ and $\\sum m_{\\nu}$. KATRIN (2025) gives $m_{\\beta}<0.45\\ \\mathrm{eV}$ (90 percent CL); oscillations require $\\sum m_{\\nu}\\ge \\sim 0.059\\ \\mathrm{eV}$ (normal) or $\\sim 0.10\\ \\mathrm{eV}$ (inverted). An answer is a nonzero value with $\\sim 20\\%$ uncertainty or a consistent upper limit across laboratory and cosmology.","problem_ref":"02ea08734e6f7503d0222ff513d71aa481eb674b5da50e563ee8a8a626fb168a","references":"","settled_by":"Cosmological detection of sum $m_{\\nu}$ at $\\ge 3\\sigma$ (DESI, Euclid, CMB-S4) cross-checked by a laboratory direct measurement (Project 8 or successors) reaching $m_{\\beta} \\sim 40\\,\\mathrm{meV}$.","status_note":"DESI DR2 plus CMB (2025) gives sum $m_{\\nu} < 0.064\\,\\mathrm{eV}$ (95 percent, LCDM), in tension with the oscillation minimum; the tension relaxes in evolving dark energy fits.","title":"What is the mass of the lightest neutrino?","topic_ref":null},"attested":{"attestation":{"batch":null,"client_id":null,"id_token_sha256":null,"kind":"platform"},"record_hash":"846959f5fe86248dafaccef362e37171a367f57e23eedd965070d9aae82b11c7","schema":"pubphys.attested/1"},"envelope":{"attested_hash":"5a310edd34f13baf506212d595f189fb1f5349d40c1923c56016b18e5cada6c8","platform_signature":{"key_id":"c6afc19b31429869751f06879c75cd64ea92654423d15b44be775bf1310a60da","sig":"R74NyWKkCimlqPxqhrWM_lH68ZBO_RF0ZmWxatDjvYi7_1IxXEHhwOT7NvDn1BQw_wxNLdXLBVN8ET7Hx80oAA"},"schema":"pubphys.envelope/1"},"record_hash":"846959f5fe86248dafaccef362e37171a367f57e23eedd965070d9aae82b11c7","leaf_index":3372}