We analyze the photoproduction helicity amplitudes for positive-parity excited baryons in the context of the $1/N_c$ expansion of QCD. The results show that subleading corrections in $1/N_c$ are important and that, while one-body effective operators are dominant, there is some evidence for the need for two-body effects.

• Received 31 December 2006

DOI:https://doi.org/10.1103/PhysRevLett.99.062002