{"paper":{"title":"Two-Loop Corrections to the Electromagnetic Vertex for Energies close to Threshold","license":"","headline":"","cross_cats":[],"primary_cat":"hep-ph","authors_text":"A.H. Hoang (University of California, San Diego)","submitted_at":"1997-03-25T00:12:04Z","abstract_excerpt":"Two-loop contributions to the electromagnetic form factors are calculated in the kinematic regime close to the fermion-antifermion threshold. The results are presented in an expansion in the velocity $\\beta$ of the fermions in the c.m. frame up to next-to-next-to leading order in $\\beta$. The existence of a new Coulomb singularity logarithmic in $\\beta$, which is closely related to the $O(\\alpha^2\\ln\\alpha)$ corrections known from positronium decays, is demonstrated. It is shown that due to this Coulomb singularity $O(\\alpha^2)$ relativistic corrections to the non-relativistic cross section of"},"claims":{"count":0,"items":[],"snapshot_sha256":"258153158e38e3291e3d48162225fcdb2d5a3ed65a07baac614ab91432fd4f57"},"source":{"id":"hep-ph/9703404","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"}