{"record":{"author":{"account_ref":null,"orcid":null},"builds_on":[],"content_schema":"pubphys.content.revision/1","content_sha256":"6c154a8ceb69e131b48cbff479ce1063861c9bed8a78032eb4f474dd61a570bf","created":"2026-10-03T07:18:07Z","files":[],"origin":{"assisted_by":[],"kind":"seed"},"parents":["5475cf5dc5b1a72283d26dc95dc6e00d7ea4e00096a7c6492e409a1816eeb011"],"salt":"bd0d78d6d1e3f7e83c660ba8d5acfe903c3f89ebd06524e831b47833cfffb3a9","schema":"pubphys.record/2","site":"pubphys.com","target":null,"type":"revision"},"content":{"answer_type":"value","assisted_by":[],"external_id":"nuc.gluon-saturation.saturation-scale-nuclei","kind":"well-posed","literature_status":"open","n":"1","parents":[],"plain":"The saturation scale is the momentum below which gluons in a nucleus are expected to be packed densely, and heavier nuclei should reach it sooner. Its actual value for gold or lead is uncertain by a large factor.","posed_since":"","precise":"Determine $Q_s^{2}(x)$ for Au and Pb at $x=1e-3\\ \\text{and}\\ 1e-4$ with uncertainty below 30 percent, including the actual A dependence (versus the naive $A^{1/3}$ scaling) and the impact-parameter profile. Estimates of order $1\\ \\text{to}\\ 2\\ \\mathrm{GeV}^{2}$ at $x\\sim 1e-3$ depend on the dipole model and the definition of $Q_s$; the answer must state the definition and the data used.","problem_ref":null,"references":"","settled_by":"A global fit of small-$x$ electron-nucleus and proton-nucleus data with nonlinear evolution, including running coupling and impact-parameter dependence, that returns $Q_s^2$ with quantified uncertainty.","status_note":"","title":"Size of the saturation scale in heavy nuclei","topic_ref":"6117d502d0793b31459e17d3b1d259c0a9c7c8e28ff50075359a3a30829f3ceb"},"attested":{"attestation":{"batch":null,"client_id":null,"id_token_sha256":null,"kind":"platform"},"record_hash":"8b3ddc17469d58250b5e83400f6f58f243d2fa0883803f18a3f20d96cd0bad2a","schema":"pubphys.attested/1"},"envelope":{"attested_hash":"edae4417055d9617b728357698ad4dfa8996d604418015610313800a87bc4387","platform_signature":{"key_id":"c6afc19b31429869751f06879c75cd64ea92654423d15b44be775bf1310a60da","sig":"IECNGLIMtnWx4t6LZIMxhGTrBl5Gdhq9MIXOwJzdxPSZ-kcbU4L2g8_vqpIw0mWCpvDg0BWTqbD37a9Y7IdDDA"},"schema":"pubphys.envelope/1"},"record_hash":"8b3ddc17469d58250b5e83400f6f58f243d2fa0883803f18a3f20d96cd0bad2a","leaf_index":1762}