Observation of a Narrow Charged State at 1876 MeV/${\mathit{c}}^2$ Decaying to an Exotic Combination of $K\pi \pi$

We report evidence for the production of a new narrow charged state in $e^{+}{e}^{-}$ annihilation at a center-of-mass energy of 4.03 GeV. This state, which has a mass of 1876± 15 MeV/${\mathit{c}}^2$, is observed in the exotic channel $K^{\mp }{\pi }^{\pm }{\pi }^{\pm }$, but not in the nonexotic channel $K^{\mp }{\pi }^{+}{\pi }^{-}$. It is produced primarily in association with a system of mass 2.01±0.02 GeV/${\mathit{c}}^2$. These characteristics are just those expected of a charged charmed meson.