Higher fully charmed tetraquarks: Radial excitations and P-wave states

We systematically calculate the mass spectrum of the higher excited fully charmed tetraquark ccc c states including the S-wave radial excitations and the P-wave states with a nonrelativistic quark model. The quark model is composed of a vector one-gluon-exchange and a scalar linear confinement interaction with the parameters determined by the charmonium spectrum. In the calculation, we consider both the 3(c) - 3(c) and the 6(c) - 6(c) color representations. For the cccc state, the 6(c) - 6(c) component is located lower than the 3(c) - 3(c) one because of the stronger attractive interactions between the diquark and antidiquark. We focus on two excited modes and their properties for the P-wave tetraquarks. The mass splitting for the rho-mode excitations with different color configurations is large. The low-lying 6(c) - 6(c) rho-mode component helps to explain the small mass gap between the ground S-wave and the P-wave tetraquark states. The recently observed X(6900) state may be the candidate of the first radially excited tetraquarks with J(PC) = 0(++) or 2(++), or the 1(+-) or 2(-+) P-wave states based on the mass spectrum. Moreover, the lowest T-c states with the exotic JPC quantum numbers 0(--) and 1(-+) may decay into the P-wave eta(c)J/psi and di-J/psi modes, respectively. The future experimental search of these T-c states will enrich the hadronic spectrum.