Eur. Phys. J. C 26, 567-577 (2003)
DOI: 10.1140/epjc/s2002-01075-4

Two-photon annihilation into baryon-antibaryon pairs

M. Diehl¹, P. Kroll² and C. Vogt<sup>3

1</sup>  Institut für Theoretische Physik E, RWTH Aachen, 52056 Aachen, Germany
²  Fachbereich Physik, Universität Wuppertal, 42097 Wuppertal, Germany
³  Nordita, Blegdamsvej 17, 2100 Copenhagen, Denmark

(Received: 3 July 2002 / Revised version: 7 October 2002 / Published online: 20 November 2002 )

Abstract
We study the handbag contribution to two-photon annihilation into baryon-antibaryon pairs at large energy and momentum transfer. We derive factorization of the process amplitude into a hard subprocess and form factors describing the soft transition, assuming that the process is dominated by configurations where the (anti)quark approximately carries the full momentum of the (anti)baryon. The form factors represent moments of time-like generalized parton distributions, so-called distribution amplitudes. A characteristic feature of the handbag mechanism is the absence of isospin-two components in the final state, which in combination with flavor symmetry provides relations among the form factors for the members of the lowest-lying baryon octet. Assuming dominance of the handbag contribution, we can describe current experimental data with form factors of plausible size, and predict the cross sections of presently unmeasured channels.

© Società Italiana di Fisica, Springer-Verlag 2003