{"schema":"pubphys.bundle/1","record":{"author":{"account_ref":null,"orcid":null},"builds_on":[],"content_schema":"pubphys.content.revision/1","content_sha256":"69a9dbe06467d0ad5a72a29e41e6b3e51a6e8442cd4fb5166285618458e6e76c","created":"2026-10-15T23:43:22Z","files":[],"origin":{"assisted_by":["ai:gpt-5.5"],"kind":"seed"},"parents":["ce59fb6cd812fc05906d0c60a71c75ea22bc686bcf38e7c3ef7010834d98ee7b","d86ae34f705bd2586690937c5318dc319451c0e3b008974a93a2a8982ef8d270"],"salt":"71254cbe14594191b4c6f6bbc45dce6cde677de56550610810365ebd00f959d4","schema":"pubphys.record/2","site":"pubphys.com","target":null,"type":"revision"},"content":{"answer_type":"mechanism","assisted_by":["ai:gpt-5.5"],"external_id":"nuc.quark-gluon-plasma.phi-spin-alignment","kind":"phenomenon","literature_status":"contested","n":"2","parents":[],"plain":"In off-center heavy-ion collisions the produced matter rotates, and spinning particles should line up slightly with the rotation. STAR found that $\\phi$ mesons (strange quark plus strange antiquark) line up far more than expected, while $K*0$ mesons do not.","posed_since":"","precise":"STAR measured the spin density-matrix element $\\rho_{00}$ of $\\phi$ and $K*0$ relative to the reaction plane in $\\mathrm{Au}+\\mathrm{Au}$ collisions at RHIC (Nature, 2023, doi 10.1038/s41586-022-05557-5): $\\rho_{00}(\\phi)$ exceeds $1/3$ well beyond the size expected from vorticity and electromagnetic fields, while $\\rho_{00}(K*0)$ is consistent with $1/3$. Determine the mechanism. Answer: a model reproducing $\\rho_{00}$ for $\\phi$ and $K*0$ versus collision energy, centrality and $p_{T}$, with predictions for $J/\\psi$ and other vector mesons.","problem_ref":"d86ae34f705bd2586690937c5318dc319451c0e3b008974a93a2a8982ef8d270","references":"","settled_by":"Measurements of $\\rho_{00}$ for $\\phi$, $K*0$ and $J/\\psi$ versus energy, rapidity and system size, compared with models that include fluctuating strong-interaction vector fields and hadronization effects.","status_note":"The 2023 result was attributed by some authors to local fluctuations of strong-force fields, without consensus as of 2026.","title":"Origin of the large global spin alignment of $\\phi$ 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