Exchange currents in photoproduction of baryon resonances

We calculate photoexcitation amplitudes for all nucleon and Δ resonances up to s = 1.6 GeV. We use a chiral quark model including two-body exchange currents. The two-body currents give important contributions. For the Δ(1232) and the D13(1520) we observe that the individual exchange current contributions considerably cancel each other while for the P11(1440), the P33(1600), and the S11(1535) we get a reinforcement of the two-body amplitudes. In comparison with present experimental data, we obtain both for the S11(1535) and for the P11(1440) amplitudes an improvement with respect to the impulse approximation.