Photoproduction of Theta+ on the nucleon and deuteron

Photoproduction of the pentaquark particle Theta^+ on the nucleon has been studied by using an isobar and a Regge model. Using the isobar model, total cross sections around 100 nb for the gamma n --> K- Theta+ channel and 400 nb for the gamma p --> {\bar K}0 Theta+ process are obtained. The inclusion of the K* intermediate state yields a substantially large effect, especially in the gamma p --> {\bar K}0 Theta+ process. The Regge approach predicts smaller cross sections, i.e., less than 100 nb (20 nb) for the process on the neutron (proton). By using an elementary operator from the isobar model, cross sections for the process on a deuteron are predicted.