{"record":{"author":{"account_ref":null,"orcid":null},"builds_on":[],"content_schema":"pubphys.content.revision/1","content_sha256":"4294a6a3906765fb80f6a0b004505ef7baeee54fb5f87d324c0106c7154d6ba7","created":"2026-10-03T07:18:07Z","files":[],"origin":{"assisted_by":[],"kind":"seed"},"parents":["5475cf5dc5b1a72283d26dc95dc6e00d7ea4e00096a7c6492e409a1816eeb011"],"salt":"bda3061949f8fa9e2e1e1a39cd7bb23fb51a82eed725ad41167041a58ca9ac7b","schema":"pubphys.record/2","site":"pubphys.com","target":null,"type":"revision"},"content":{"answer_type":"classification","assisted_by":[],"external_id":"nuc.exotic-hadrons.hybrid-meson-spectrum","kind":"well-posed","literature_status":"open","n":"1","parents":[],"plain":"Hybrid mesons contain a quark, an antiquark and an excited gluon field, and some have spin-parity combinations impossible for a plain quark-antiquark pair. A few candidates exist, and whether they form the complete family predicted by lattice QCD is open.","posed_since":"","precise":"Lattice QCD predicts a lightest hybrid multiplet including a $J^{PC} = 1-+$ nonet between about $1.6\\text{ and }2.0\\ \\mathrm{GeV}$. Establish whether $\\pi1(1600)$ is the only isovector $1-+$ state below $2\\ \\mathrm{GeV}$ (a 2019 JPAC analysis described $\\pi1(1400)$ and $\\pi1(1600)$ as one pole), and whether $\\eta1(1855)$ (BESIII, 2022) and an isoscalar partner complete the nonet. Answer: masses, widths and decay patterns of the $1-+$ nonet members.","problem_ref":null,"references":"","settled_by":"Partial-wave analyses of GlueX photoproduction, COMPASS/AMBER pion-beam data and BESIII $J/\\psi$ decays establishing all members of the $1-+$ nonet.","status_note":"The single-pole pi1 interpretation (2019) and the eta1(1855) observation (2022) awaited independent confirmation as of 2026.","title":"Spectrum of light hybrid mesons with exotic quantum numbers","topic_ref":"0a95c0555eb6bb05e3999da7d5dca17d55ffdaf922ee81ba9f8dcd197324eda0"},"attested":{"attestation":{"batch":null,"client_id":null,"id_token_sha256":null,"kind":"platform"},"record_hash":"73aa0caa5dad93afeb574023ff7cca379c750b2257789f2607f170668ec499ee","schema":"pubphys.attested/1"},"envelope":{"attested_hash":"71db6e86dba3815a9710fe8d1252b5c56fc0d52703dd518080fdcc5bad321ae7","platform_signature":{"key_id":"c6afc19b31429869751f06879c75cd64ea92654423d15b44be775bf1310a60da","sig":"0v009JIBMLT2jvx7U1LLtmSk8IgUNGSXmknInEIJDOZkPyaYPSU9912eo_axBrs7rR2RkHB0oegfodrkSIvUBQ"},"schema":"pubphys.envelope/1"},"record_hash":"73aa0caa5dad93afeb574023ff7cca379c750b2257789f2607f170668ec499ee","leaf_index":1746}