Electroproduction of the Roper resonance on the proton: the role of the   three-quark core and the molecular N-sigma component
  The Roper resonance is considered as a mixed state of a three-quark core configuration and a hadron molecular component N+sigma. Based on this ansatz we study electroproduction of the Roper resonance. The strong and electromagnetic couplings induced by the quark core are calculated in the 3P0 model. The contribution of the vector meson cloud to the electromagnetic transition is given in the framework of the VMD model. Results are compared with the recent JLab electroproduction data. 
Igor T. Obukhovsky, Amand Faessler, Dimitry K. Fedorov, Thomas   Gutsche, Valery E. Lyubovitskij
hep-ph