Photoproduction signatures of hybrid baryons: An application of the quark model with gluonic degrees of freedom

An application of the quark model with gluonic degrees of freedom to hybrid baryons is discussed. The photon-gluon transition operator for the process γq→qG is added to the electromagnetic interaction, where it plays an explicit role in quark-gluon systems. The successes of the three-valence-quark model in describing the magnetic moments of baryons is preserved in the new model. It is shown that the Barnes-Close selection rule for hybrid baryons (${\mathit{q}}^3$G states) is equivalent to the Moorhouse selection rule for conventional P-wave baryons (${\mathit{q}}^3$ states). We predict a gluonic partner of the nucleon with the same ratio of magnetic moments. It is possible that the Roper resonance ${\mathit{P}}_{11}$(1440) is such a state. The phenomenological implications of such an assignment and important tests accessible to forthcoming photoproduction experiments at CEBAF are discussed.