{"record":{"author":{"account_ref":null,"orcid":null},"builds_on":[],"content_schema":"pubphys.content.revision/1","content_sha256":"80d382ee3ee2c2a922be5e710badfd82b94e03aad20dd103e8d41570add40c6e","created":"2026-10-03T07:18:07Z","files":[],"origin":{"assisted_by":[],"kind":"seed"},"parents":["5475cf5dc5b1a72283d26dc95dc6e00d7ea4e00096a7c6492e409a1816eeb011"],"salt":"4a3910d2080643c1032294dbc5114206347556274cf6954b7e9e7cbd293baf6d","schema":"pubphys.record/2","site":"pubphys.com","target":null,"type":"revision"},"content":{"answer_type":"mechanism","assisted_by":[],"external_id":"nuc.emc-src.emc-origin","kind":"phenomenon","literature_status":"contested","n":"1","parents":[],"plain":"Per nucleon, a heavy nucleus has fewer quarks carrying 30 to 70 percent of a nucleon's momentum than deuterium has. Whether all nucleons are slightly modified or only those in close pairs are strongly modified is unknown.","posed_since":"1983","precise":"The per-nucleon ratio $F2^{A}(x)/F2^{d}(x)$ of deep-inelastic structure functions falls below 1 for $0.3 < x < 0.7$, with slope correlated with $a_{2}$, the number of short-range correlated (SRC) pairs per nucleon. Determine the mechanism: mean-field modification of all nucleons, strong modification of nucleons in high-virtuality SRC pairs, or another effect. Answer: a model reproducing the A- and x-dependence that is also consistent with tagged and flavor-separated measurements.","problem_ref":null,"references":"","settled_by":"Spectator-tagged deep-inelastic scattering on deuterium at several recoil momenta, combined with flavor-separated EMC measurements.","status_note":"The linear EMC-SRC correlation (CLAS, Nature 2019) supports the SRC picture but did not exclude mean-field models as of 2026.","title":"Physical origin of the EMC effect","topic_ref":"7a074c9c279467b77e19375da4dad17647254ffcdf3c39de667bd47e1e1c500e"},"attested":{"attestation":{"batch":null,"client_id":null,"id_token_sha256":null,"kind":"platform"},"record_hash":"bbe8d97ea817eaaa690cc2570dda16cc32c1e41c3503957a678054bd299643a3","schema":"pubphys.attested/1"},"envelope":{"attested_hash":"48c102cfce2f735e64ba824c699a1ba28e1134acc14b6388cf38da0cfa7118fc","platform_signature":{"key_id":"c6afc19b31429869751f06879c75cd64ea92654423d15b44be775bf1310a60da","sig":"ANhCbpzK2hzLJpdKkzgRu_6TjlzKZRQLKAqMwJ9kgCHSOAH4SlztKGagEVMiMdG3RacSa_-LvXTSfJuOlDDbAQ"},"schema":"pubphys.envelope/1"},"record_hash":"bbe8d97ea817eaaa690cc2570dda16cc32c1e41c3503957a678054bd299643a3","leaf_index":1740}