Spin observables and the determination of the parity of $\Theta^+$ in photoproduction reactions

Abstract

Spin observables in the photoproduction of the $\Theta^+$ are explored for the purpose of determining the parity of the $\Theta^+$. Based on reflection symmetry in the scattering plane, we show that certain spin observables in the photoproduction of the $\Theta^+$ can be related directly to its parity. We also show that measurements of both the target nucleon asymmetry and the $% \Theta^+$ polarization may be useful in determining the parity of $\Theta^+$ in a model-independent way. Furthermore, we show that no combination of spin observables involving only the polarization of the photon and/or nucleon in the initial state can determine the parity of $\Theta^+$ unambiguously.