{"record":{"author":{"account_ref":null,"orcid":null},"builds_on":[],"content_schema":"pubphys.content.revision/1","content_sha256":"afcadfcd56717648791c2b58d0c04a8c0f49cc918cf29e533846094db53afc28","created":"2026-10-15T23:43:22Z","files":[],"origin":{"assisted_by":[],"kind":"seed"},"parents":["8b3ddc17469d58250b5e83400f6f58f243d2fa0883803f18a3f20d96cd0bad2a","ce59fb6cd812fc05906d0c60a71c75ea22bc686bcf38e7c3ef7010834d98ee7b"],"salt":"0499a7c95c6b11e8bc9fa7b1efbb0ee8b49b56d439f8891b1cba38bf69169259","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":"2","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 $x=10^{-3}\\ \\text{and}\\ 10^{-4}$ 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 $x\\sim 10^{-3}$ depend on the dipole model and the definition of $Q_s$; the answer must state the definition and the data used.","problem_ref":"8b3ddc17469d58250b5e83400f6f58f243d2fa0883803f18a3f20d96cd0bad2a","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":null},"attested":{"attestation":{"batch":null,"client_id":null,"id_token_sha256":null,"kind":"platform"},"record_hash":"28958909bf9004743e0850bddc047b9ef22638b1dec0985009aa0342a581be4b","schema":"pubphys.attested/1"},"envelope":{"attested_hash":"67ff32974b2a65b130585dcb64bd6d1d76a91af86d12eb14df7ea7d300f27c6a","platform_signature":{"key_id":"c6afc19b31429869751f06879c75cd64ea92654423d15b44be775bf1310a60da","sig":"XJ3Bkexg3vLIVZBU8FZb0-B9MNb7WEAQRmyVlqsSLI6fdo-bby3uAq0hrP9bZpa6zfbVMwLAs8aK04z57QauDQ"},"schema":"pubphys.envelope/1"},"record_hash":"28958909bf9004743e0850bddc047b9ef22638b1dec0985009aa0342a581be4b","leaf_index":3504}