The role of vector-baryon channels and resonances in the $\gamma p \to K^0 \Sigma^+$ and $\gamma n \to K^0 \Sigma^0$ reactions near the $K^* \Lambda$ threshold

Abstract

We have studied the $\gamma p \to K^0 \Sigma^+$ reaction in the energy region around the $K^* \Lambda$ and $K^* \Sigma$ thresholds, where the CBELSA/TAPS cross section shows a sudden drop and the differential cross section experiences a transition from a forward-peaked distribution to a flat one. Our coupled channel model incorporates the dynamics of the vector meson-baryon interaction which is obtained from the hidden gauge formalism. We find that the cross section in this energy region results from a delicate interference between amplitudes having $K^* \Lambda$ and $K^*\Sigma$ intermediate states. The sharp downfall is dictated by the presence of a nearby $N^*$ resonance produced by our model, a feature that we have employed to predict its properties. We also show results for the complementary $\gamma n \to K^0 \Sigma^0$ reaction, the measurement of which would test the mechanism proposed in this work.