EXCLUSIVE PHOTOPRODUCTION OF LARGE MOMENTUM-TRANSFER K-MESON AND K-ASTERISK-MESON

The reactions gamma p-->K(+)Lambda and gamma p-->K(+)Lambda: are anal yzed within perturbative QCD, allowing for diquarks as quasielementary constituents of baryons. The diquark-model parameters and the quark-d iquark distribution amplitudes of the proton and Lambda are taken from previous investigations of electromagnetic baryon form factors and Co mpton scattering off protons. Unpolarized differential cross sections and polarization observables are computed for different choices of the K and K distribution amplitudes. The asymptotic form of the K distri bution amplitude (proportional to x(1)x(2)) is found to provide a sati sfactory description of the K photoproduction data.