CoherentΘ+andΛ(1520)photoproduction off the deuteron

Abstract

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