p ( rvec. gamma. ,. pi. sup 0 ) reaction and the E 2 excitation of the. Delta

Results from three independent measurements of the {ital p}({rvec {gamma}},{pi}{sup 0}) reaction are presented for incident photon energies between 243 and 314 MeV, and for c.m. angles of 105{degree}, 122{degree}, and 150{degree}. The ratio of cross sections measured with orthogonal states of linear polarization is sensitive to the {ital E}2 excitation of the {Delta} resonace. Comparisons are made to the predictions of various models, all of which fail to reproduce these data.