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

Abstract

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 $n{K}^{+}$ invariant mass distribution when the $p{K}^{-}$ 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 $p{K}^{-}$ 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.

Comments: 34 pages, 22 figures