title: Exclusive annihilation pp-->gammagamma in a generalized Parton picture.
abstract: Exclusive proton-antiproton annihilation into two photons at large s ( approximately 10 GeV2) and /t/,/u/ approximately s can be described by a generalized parton picture analogous to the "soft mechanism" in wide-angle real Compton scattering. The two photons are emitted in the annihilation of a single fast quark and antiquark. The matrix element describing the transition of the pp system to a qq pair can be related to the timelike proton elastic form factors as well as to the quark/antiquark distributions measured in inclusive deep-inelastic scattering. The reaction could be studied with the proposed 1.5-15 GeV high-luminosity antiproton storage ring (HESR) at GSI.
authors.affiliation: Institut für Theoretische Physik, Universität Regensburg, D-93053 Regensburg, Germany.
authors.forename: A
authors.initials: A
authors.lastname: Freund
authors.forename: A V
authors.initials: AV
authors.lastname: Radyushkin
authors.forename: A
authors.initials: A
authors.lastname: Schäfer
authors.forename: C
authors.initials: C
authors.lastname: Weiss