{"record":{"author":{"account_ref":null,"orcid":null},"builds_on":[],"content_schema":"pubphys.content.revision/1","content_sha256":"095cd462e992623ec49075946bf106902c39552d3a3cb983a8308d9ba6b8852e","created":"2026-10-15T23:43:22Z","files":[],"origin":{"assisted_by":["ai:gpt-5.5"],"kind":"seed"},"parents":["24e1c781aa086d22f90ffb308030079c2dbee63dd58a84fd6b0dbfc8829e7d82","ce59fb6cd812fc05906d0c60a71c75ea22bc686bcf38e7c3ef7010834d98ee7b"],"salt":"be53f58becc30669971a4201437de44872675f879652a1717ab30cd7651447a8","schema":"pubphys.record/2","site":"pubphys.com","target":null,"type":"revision"},"content":{"answer_type":"value","assisted_by":["ai:gpt-5.5"],"external_id":"nuc.exotic-hadrons.x3872-compositeness","kind":"well-posed","literature_status":"open","n":"2","parents":[],"plain":"The chi_c1(3872), also called $X(3872)$, lies within about 0.2 MeV of the combined mass of two charmed mesons, $D0$ and $\\mathrm{anti}-D*0$. Measuring its exact position and line shape decides how much of it is a loose two-meson molecule.","posed_since":"2003","precise":"Determine the pole position of chi_c1(3872) relative to the D0 anti-$D*0$ threshold, including the finite D*0 width, and its Weinberg compositeness $1 - Z$ ($Z = 0\\ \\text{pure molecule}, Z = 1\\ \\text{compact state}$) from the $D0\\ \\text{anti-D0}\\ \\pi0\\ \\text{and}\\ J/\\psi\\ \\pi+\\ \\pi-$ line shapes. Answer: binding energy with about $10\\,\\mathrm{keV}$ precision and Z with uncertainty below 0.1.","problem_ref":"24e1c781aa086d22f90ffb308030079c2dbee63dd58a84fd6b0dbfc8829e7d82","references":"","settled_by":"A direct energy scan in antiproton-proton annihilation (PANDA at FAIR) or high-statistics $D0\\ \\mathrm{anti}-D0\\ \\pi0$ line shapes at LHCb or Belle II.","status_note":"LHCb line-shape analyses (2020) placed the pole very close to threshold, consistent with a quasi-bound state, without fixing Z.","title":"Compositeness of chi_c1(3872) from its line shape","topic_ref":null},"attested":{"attestation":{"batch":null,"client_id":null,"id_token_sha256":null,"kind":"platform"},"record_hash":"414e6bec9478096bb392320805b23ad1220903039fe0e53aa27996ec7d528316","schema":"pubphys.attested/1"},"envelope":{"attested_hash":"78bfd6b6f67e2d261d2f5010f299ee534822aa5ebd3845c37b80c300c42d2be2","platform_signature":{"key_id":"c6afc19b31429869751f06879c75cd64ea92654423d15b44be775bf1310a60da","sig":"ZyZGZRYUHOyNifbdY3zw2-Bfgopj1Yndbfd-K69IC0gEoYV_N3Tsds9ItMjFCBonOB5_Xj1F2ie5_-O7gy6cBA"},"schema":"pubphys.envelope/1"},"record_hash":"414e6bec9478096bb392320805b23ad1220903039fe0e53aa27996ec7d528316","leaf_index":3496}