Observation of Two Narrow States Decaying into $Ξ_{c}^{+}γ$ and $Ξ_{c}^{0}γ$

Abstract

We report the first observation of two narrow charmed strange baryons decaying to $Ξ_c^+γ$ and $Ξ_c^0γ$, respectively, using data from the CLEO II detector at CESR. We interpret the observed signals as the $Ξ_c^{+\prime}(c{su})$ and $Ξ_c^{0\prime}(c{sd})$, the symmetric partners of the well-established antisymmetric $Ξ_c^+(c[su])$ and $Ξ_c^0(c[sd])$. The mass differences $M(Ξ_c^{+\prime})-M(Ξ_c^+)$ and $M(Ξ_c^{0\prime})-M(Ξ_c^0)$ are measured to be $107.8\pm 1.7\pm 2.5$ and $107.0\pm 1.4\pm 2.5 MeV/c^2$, respectively.