{"paper":{"title":"The $\\gamma \\gamma \\to J/\\psi J/\\psi$ reaction and the $J/\\psi J/\\psi$ pair production in exclusive ultraperipheral ultrarelativistic heavy ion collisions","license":"http://arxiv.org/licenses/nonexclusive-distrib/1.0/","headline":"","cross_cats":[],"primary_cat":"hep-ph","authors_text":"Anna Cisek, Antoni Szczurek, Mariola K{\\l}usek-Gawenda, Sergey Baranov, Wolfgang Sch\\\"afer","submitted_at":"2012-08-29T13:53:52Z","abstract_excerpt":"We calculate the cross section for the $\\gamma \\gamma \\to J/\\psi J/\\psi$ process. Two mechanisms are considered: box (two-loop) diagrams of the order of $O(\\alpha_{em}^2 \\alpha_s^2)$ and two-gluon exchange of the order of $O(\\alpha_{em}^2 \\alpha_s^4)$. The first mechanism is calculated in the heavy-quark non-relativistic approximation while the second case we also include the effects of quantum motion of quarks in the bound state. The box contribution dominates at energies close to the threshold ($W <$ 15 GeV) while the two-gluon mechanism takes over at $W >$ 15 GeV. Including the bound-state "},"claims":{"count":0,"items":[],"snapshot_sha256":"258153158e38e3291e3d48162225fcdb2d5a3ed65a07baac614ab91432fd4f57"},"source":{"id":"1208.5917","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"}