Some aspects of ${\mathrm{\Theta }}^{+}$ parity determination in the reaction $\gamma N\to {\mathrm{\Theta }}^{+}\bar{K}\to NK\bar{K}$

We analyze the problem of how to determine the parity of the ${\mathrm{\Theta }}^{+}$ pentaquark in the reaction $\gamma N\to K\mathrm{\Theta }\to NK\bar{K}$, where $N=n,p$. Our model calculations indicate that the contribution of the non-resonant background of the reaction $\gamma N\to NK\bar{K}$ cannot be neglected, and that suggestions to determine the parity based solely on the initial-stage process $\gamma N\to K\mathrm{\Theta }$ cannot be implemented cleanly. We discuss the various mechanisms that contribute to the background, and we identify some spin observables which are sensitive.