Hidden charm pentaquarks: mass spectrum, magnetic moments, and photocouplings.

We develop an extension of the usual three-flavor quark model to four flavors (u, d, s and c), and discuss the classification of pentaquark states with hidden charm (qqqc (c) over bar). We fit our model to the known baryon spectrum and we predict the double and triple charm baryons, finding good agreement with the most recent lattice QCD calculations. We compute the ground state of hidden charm pentaquarks and their associated magnetic moments and electromagnetic couplings, of interest to pentaquark photoproduction experiments.