Hard Exclusive Baryon-Antibaryon Production in Two-Photon Collisions

We study baryon pair production in two-photon collisions, gamma gamma -> B Bbar, within perturbative quantum chromodynamics, treating baryons as quark-diquark systems. We extend previous work within the same approach by treating constituent-mass effects systematically by means of an expansion in the small parameter (mass/photon energy). Our approach enables us to give a consistent description of the cross sections for all octet baryon channels. Adopting the model parameters from foregoing work, we are able to reproduce the most recent large-momentum-transfer data from LEP for the p pbar, Lambda Lambdabar, and Sigma^0 Sigma^0bar channels in a quite satisfactory way. We also briefly address the crossed process for the proton channel, gamma p -> gamma p.