Coherent Theta+ and Lambda(1520) photoproduction off the deuteron

We analyze an effect of the coherent Theta+Lambda(1520) photoproduction in gamma D interaction near the threshold. We demonstrate that the coherence effect becomes manifest in a comparison of the nK+ invariant mass distribution when the pK- invariant equals the Lambda(1520) mass. Our model calculations indicate a sizeable contribution of resonant and non-resonant background processes in the gamma D to np K+K- reaction which generally exceed the contribution of the coherent resonant channel. However, we find that the coherent Theta+Lambda(1520) photoproduction is enhanced relative to the background processes in the forward hemisphere of the pK- pair photoproduction. Moreover, the coherence effect does not depend on the Theta+ photoproduction amplitude and is defined by the probabilities of the Lambda(1520) photoproduction and the Theta+ to NK transition. Therefore, this coherence effect may be used as an independent method for studying the mechanism of Theta+ production and Theta+ properties.