Negative parity pentaquarks in large N_c QCD and quark model

Recently, the 1/N_c expansion has been applied to the study of exotic baryons containing both quarks and antiquarks. We extend this approach to exotic states with mixed-symmetric spin-flavor symmetry, which correspond in the quark model to negative parity pentaquarks, and discuss the large N _c predictions for their mass spectrum. The heavy exotics Q̄q⁴ transform as 3, 6, 15 and 15′ under SU(3), while the light states q̄q⁴ include the exotic multiplets 10, 27, 35. We give mass relations among these multiplets in the 1/N_c expansion. In the quark model, the mass splittings between these states are given by color-spin interactions. Using the observation of an anticharmed exotic by the H1 Collaboration, we give predictions for the masses of other expected heavy pentaquarks.