Puzzle of the Λ_c Spectrum

There is a puzzle in the Λ_c⁺ family, i.e., one member with J^P=3/2⁺ is missing in a L=2 multiplet which the heavy quark effective theory predicts, and J^P's of Λ_c(2765)⁺ and Λ_c(2940)⁺ are unknown. Using a light diquark picture to calculate baryon masses, we study possible assignments of two Λ_c's with unknown J^P and the missing Λ_c⁺ with 3/2⁺ for L=2, and we find the most probable possibility that the peak corresponding to Λ_c(2880)⁺ actually includes a missing member with spin 3/2⁺ for L=2 and that quantum numbers of Λ_c(2765)⁺ and Λ_c(2940)⁺ are 2S(1/2⁺) and 2P (1/2^-), respectively.