Negative parity pentaquarks in large Nc QCD and quark model

Abstract

Recently, the 1/Nc 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/Nc 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. © 2005 The American Physical Society.