Quark model study of the η photo-production:: Evidence for a new S11 resonance?

An extensive and systematic study of the recent eta photo-production data up to 1.2 GeV is presented within a chiral constituent quark model. A model embodying all known nucleonic resonances shows clear need for a yet undiscovered third S-11 resonance in the second resonance region, for which we determine the mass (1.729 GeV) and the total width (183 MeV). Furthermore, we extract the configuration mixing angles, an important property of the quark-quark interaction in the quark model, for the resonances S-11(1535) and S-11(1650), as well as for the resonances D-13(1520) and D-13(1700). Our results agree well with the quark model predictions. In addition, the partial etaN decay, widths and/or the photo-excitation helicity amplitudes for the nucleonic resonances S-11(1535), S-11(1650), P-11(1710), P-13(1720), D-13(1520), D-13(1700), D-15(1675), and F-15(1680) are also obtained in this approach.