Photoproduction of excited baryons in the 1 /Nc expansion of QCD

we present results for the photoproduction helicity amplitudes of excited baryons obtained in the context of the 1 /nc expansion of qcd. the results show that, in order to get a satisfactory description of the observed photoproduction amplitudes, the sub-leading corrections in 1/nc are important. we also find that, while one-body effective operators are dominant, there is some evidence for the need of two-body effects which, in general, are not included in quark model calculations.