Recent Results Of Charged Pion And Kaon Photoproduction On The Proton At Spring-8/Leps

We carry out photoproduction experiments by using linearly polarized photon beams with energies of 1.5-3 GeV at SPring-8/LEPS. One of our physics motivations is to understand reaction mechanisms of hadron photoproduction. We study (1) (gamma) over right arrowp -> pi(-)Delta(++), (2) (gamma) over right arrowp -> pi(+)n, (3) (gamma) over right arrowp -> K+Lambda(K+Sigma(0)), and (4) (gamma) over right arrowp -> pi(+)Delta(0) reactions which produce (1) uu, (2) d (d) over bar, (3) ss, and (4) d (d) over bar quark-antiquark pairs in the final state. Differential cross sections and photon beam asymmetries have been measured at forward meson angles of 0.6 < cos theta(cm) <1. Precise comparison between the pi(-)Delta(++) and pi(+)Delta(0) reactions plays an important role in the study of nucleon resonances. It enables to distinguish between N* and Delta* by taking the cross section ratios of the two reactions. We have measured preliminary cross section ratios d sigma(pi(+)Delta(0))/d sigma(pi(-)Delta(++)). The ratios are found to be close to 1/3, which is expected from the exchange of isospin=1 in the t channel, for 0.966< cos theta(cm) <1 and all the photon energies. The ratios become larger than 1/3 and close to 1 for larger angles and higher energy regions. The larger ratios might be due to Delta resonances, giving the ratio 4/3, excited in the intermediate state