{"record":{"author":{"account_ref":null,"orcid":null},"builds_on":[],"content_schema":"pubphys.content.revision/1","content_sha256":"cc1bae0dfd9a2aaf88d89a25869c6fb48e38635754d5e45b96fbc34883885770","created":"2026-10-15T23:43:22Z","files":[],"origin":{"assisted_by":[],"kind":"seed"},"parents":["65cad78542e44a39679ea3d379ed3054dc7d8a4646c2b5074fca3f9f2164231f","ce59fb6cd812fc05906d0c60a71c75ea22bc686bcf38e7c3ef7010834d98ee7b"],"salt":"f1b36d0b40db6e81909acde89093e3c75064a8bed1259827563db4e2a40742e6","schema":"pubphys.record/2","site":"pubphys.com","target":null,"type":"revision"},"content":{"answer_type":"value","assisted_by":[],"external_id":"nuc.proton-structure.gluon-helicity","kind":"well-posed","literature_status":"open","n":"2","parents":[],"plain":"Gluons, the particles that bind quarks, can carry spin aligned with the proton's. Collider data show a positive contribution from medium-momentum gluons, but the part from very low-momentum gluons is unknown.","posed_since":"","precise":"Determine $\\Delta G(\\mu^{2})=\\int_{0}^{1}\\mathrm{d}x\\ \\Delta g(x,\\mu^{2})$ at $\\mu^{2}=10\\ \\mathrm{GeV}^{2}$, where $\\Delta g$ is the gluon helicity distribution and x the gluon momentum fraction. RHIC polarized pp data give $\\int_{0.05}^{0.2}\\Delta g\\ \\mathrm{d}x=0.20\\ (+0.06,-0.07)$ (de Florian et al., 2014) under a positivity assumption; the open part is $x<0.01$, where no data exist, together with the residual dependence of the sign on high-x and $\\mathrm{SU}(3)$ assumptions. Answer: $\\Delta G$ with total uncertainty below 0.05.","problem_ref":"65cad78542e44a39679ea3d379ed3054dc7d8a4646c2b5074fca3f9f2164231f","references":"","settled_by":"Scaling violations of the polarized structure function $g_{1}$ measured at the EIC over $10^{-4} < x < 0.5$, combined in a global fit with RHIC data.","status_note":"Fits without positivity admitted negative $\\Delta g$ (JAM, 2022); lattice Ioffe-time data could not fix the sign (Karpie et al., 2023), but adding high-x polarized DIS data disfavored the negative solution (Hunt-Smith et al., 2024); the $x < 0.01$ contribution remained unmeasured as of 2026.","title":"Total gluon spin contribution $\\Delta G$ to the proton spin","topic_ref":null},"attested":{"attestation":{"batch":null,"client_id":null,"id_token_sha256":null,"kind":"platform"},"record_hash":"5f16c95ef7800280d40ca22a682434ad405547ab3988678e4025a65c74f108d9","schema":"pubphys.attested/1"},"envelope":{"attested_hash":"b651da328c733b3da068a87fe262f5e15b2b561bbb567f9b5963f561717317cd","platform_signature":{"key_id":"c6afc19b31429869751f06879c75cd64ea92654423d15b44be775bf1310a60da","sig":"PMrfoYb6nPQe0HbE3RF1nH0HHkDEJ4ZRx2vlZxcf4iY9k4xHVau8naTSSEDRuV5Z6VUs9p3B8PvNOa1xYcx2Cg"},"schema":"pubphys.envelope/1"},"record_hash":"5f16c95ef7800280d40ca22a682434ad405547ab3988678e4025a65c74f108d9","leaf_index":3522}