{"paper":{"title":"The $\\eta_c\\gamma \\gamma ^*$ transition form factor in the decay $\\eta_c\\to \\gamma \\ell^+\\ell^-$ and in the crossed channels $\\gamma e^-\\to \\eta_c e^- $ and $e^+e^-\\to\\eta_c\\gamma","license":"","headline":"","cross_cats":[],"primary_cat":"hep-ph","authors_text":"Egle Tomasi-Gustafsson, Elvio Di Salvo, Michail P. Rekalo","submitted_at":"2000-04-12T14:14:39Z","abstract_excerpt":"The Dalitz distribution and the effective mass spectrum of the lepton pair produced in the decay $\\eta_c\\to \\gamma \\ell^+ \\ell^-$, as well as the differential cross sections for the crossed channels $\\gamma e^-\\to \\eta_c e^- $ and $e^+ e^-\\to \\eta_c \\gamma$, are calculated in terms of the sole electromagnetic transition form factor for the vertex $\\eta_c\\to\\gamma \\gamma^*$, where $\\gamma^*$ is a virtual photon with a space-like (for $\\gamma e^- \\to \\eta_c e^- $) or a time-like (for $e^+ e^-\\to \\eta_c \\gamma$ and $\\eta_c\\to\\gamma \\ell^+\\ell^-$) four-momentum. Explicit parametrisations of the tr"},"claims":{"count":0,"items":[],"snapshot_sha256":"258153158e38e3291e3d48162225fcdb2d5a3ed65a07baac614ab91432fd4f57"},"source":{"id":"hep-ph/0004112","kind":"arxiv","version":1},"verdict":{"id":null,"model_set":{},"created_at":null,"strongest_claim":"","one_line_summary":"","pipeline_version":null,"weakest_assumption":"","pith_extraction_headline":""},"references":{"count":0,"sample":[],"resolved_work":0,"snapshot_sha256":"258153158e38e3291e3d48162225fcdb2d5a3ed65a07baac614ab91432fd4f57","internal_anchors":0},"formal_canon":{"evidence_count":0,"snapshot_sha256":"258153158e38e3291e3d48162225fcdb2d5a3ed65a07baac614ab91432fd4f57"},"author_claims":{"count":0,"strong_count":0,"snapshot_sha256":"258153158e38e3291e3d48162225fcdb2d5a3ed65a07baac614ab91432fd4f57"},"builder_version":"pith-number-builder-2026-05-17-v1"}