title: Two-photon decays of charmonia from lattice QCD.
abstract: We make the first calculation in lattice QCD of two-photon decays of mesons. Working in the charmonium sector, using the Lehmann-Symanzik-Zimmermann reduction to relate a photon to a sum of hadronic vector eigenstates, we compute form factors in both the spacelike and timelike domains for the transitions eta c --> gamma*gamma* and chi(c0) --> gamma*gamma*. At the on-shell point, we find approximate agreement with experimental world-average values.
authors.affiliation: Jefferson Laboratory MS 12H2, 12000 Jefferson Avenue, Newport News, Virginia 23606, USA. dudek@jlab.org
authors.forename: Jozef J
authors.initials: JJ
authors.lastname: Dudek
authors.forename: Robert G
authors.initials: RG
authors.lastname: Edwards