Flavor-singlet charm pentaquark
Abstract
A new type of charm pentaquark Pcs with quark content ccuds in light-flavor singlet state is studied in the quark model. This state is analogous to the Pc with ccuud in light-flavor octet, which was observed in LHC in 2015. Considering various combinations of color, spin and light flavor as internal quantum numbers in Pcs, we investigate the mass ordering of the Pcs's by adopting both the one-gluon exchange interaction and the instanton-induced interaction in the quark model. The most stable configuration of Pcs is identified to be total spin 1/2 in which the cc is combined to be color octet and spin 1, while the uds cluster is in a color octet state. The other color octet configurations, the total spin 1/2 state with the cc spin 0 and the state with total spin 3/2 and cc spin 1, are found as excited states. We also discuss possible decay modes of these charm pentaquarks.