{"record":{"author":{"account_ref":null,"orcid":null},"builds_on":[],"content_schema":"pubphys.content.revision/1","content_sha256":"e487a16bbc2f226af4fca4f7ea34637775ebcc08bad6ed347e0b635c26be8f0d","created":"2026-10-03T07:18:07Z","files":[],"origin":{"assisted_by":[],"kind":"seed"},"parents":["5475cf5dc5b1a72283d26dc95dc6e00d7ea4e00096a7c6492e409a1816eeb011"],"salt":"ab18cc27b80ace8b9548e4cb4880fabce5c8eb015ce509526a94173d93f83097","schema":"pubphys.record/2","site":"pubphys.com","target":null,"type":"revision"},"content":{"answer_type":"mechanism","assisted_by":[],"external_id":"nuc.quark-gluon-plasma.phi-spin-alignment","kind":"phenomenon","literature_status":"contested","n":"1","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":null,"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 $\\phi$ mesons","topic_ref":"ec5bb29d3c4ec6576273c8009fdd00011a21f5672430b3080013ab67a0a1a41c"},"attested":{"attestation":{"batch":null,"client_id":null,"id_token_sha256":null,"kind":"platform"},"record_hash":"d86ae34f705bd2586690937c5318dc319451c0e3b008974a93a2a8982ef8d270","schema":"pubphys.attested/1"},"envelope":{"attested_hash":"01f9421daad1c45a36942f1834f43efe37798b5c51b24861da0174f83d5f9d42","platform_signature":{"key_id":"c6afc19b31429869751f06879c75cd64ea92654423d15b44be775bf1310a60da","sig":"mr74MtYnl5rgSoVzenSLHFqC8YLZEpQ3s8sHAgexg0fQKAeWRY4iuzVR3gsXtPjDIUIiQlRMqCGji6UW1dlYBg"},"schema":"pubphys.envelope/1"},"record_hash":"d86ae34f705bd2586690937c5318dc319451c0e3b008974a93a2a8982ef8d270","leaf_index":1805}