Observation of a narrow pentaquark state, $P_c(4312{)}^{+}$, and of two-peak structure of the $P_c(4450{)}^{+}$

LHCb collaboration, R. Aaij, C. Abellán Beteta +866

A narrow pentaquark state, $P_c(4312{)}^{+}$, decaying to $J/\psi p$ is discovered with a statistical significance of $7.3\sigma$ in a data sample of ${\Lambda }_b^0\to J/\psi p{K}^{-}$ decays which is an or…