Exclusive photoproduction of large momentum-transfer K and K* mesons

The reactions gamma p-->K(+)Lambda and gamma p-->K*(+)Lambda: are analyzed within perturbative QCD, allowing for diquarks as quasielementary constituents of baryons. The diquark-model parameters and the quark-diquark distribution amplitudes of the proton and Lambda are taken from previous investigations of electromagnetic baryon form factors and Compton 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 distribution amplitude (proportional to x(1)x(2)) is found to provide a satisfactory description of the K photoproduction data.