Investigating the parity of the exotic Theta^+ baryon from the kaon photoproduction

Based on the hadronic model with the gauge prescription suggested by Ohta and Haberzettl, we investigate the possibility of determining the parity state of the $\Theta^+$ baryon using photon induced processes, $\gamma n\to K^- \Theta^+$ and $\gamma p\to \bar{K}^0 \Theta^+$. The total and differential cross sections are simulated in two versions of pseudovector(PV) and pseudoscalar(PS) coupling schemes and the results are reported both on the positive and negative parity states of the $\Theta^+$ baryon. It is found that in both coupling schemes the total cross sections from the neutron target are in general larger than those from the proton target, regardless of the $\Theta^+$ parities. The cross sections of the $\Theta^+$ production however depend largely on the value of the $\Theta^+$ decay width which is not yet well established. Moreover, there is a wide theoretical uncertainty associated with the different assumption on the gauge prescription in model calculations. We discuss these points by comparing theoretical predictions with the existing experimental data. Our analysis suggests that the observation of the angular distribution rather than just the total cross section in the photoproduction process may be a useful tool to distinguish the parity of the $\Theta^+$ baryon.