Observation of two narrow states decaying into Xi(+)(c)gamma and Xi(0)(c)gamma

Abstract

We report the first observation of two narrow charmed strange baryons decaying to Xi(c)(+) gamma and Xi(c)(0)gamma, respectively, using data from the CLEO II detector at the Cornell Electron Storage Ring. We interpret the observed signals as the Xi(c)(+/) (c{su}) and Xi(c)(0/) (c{sd}), the symmetric partners of the well-established antisymmetric Xi(c)(+) (c[su]) and Xi(c)(0) (c[sd]). The mass differences M(Xi(c)(+/)) - M(Xi(c)(+)) and M(Xi(c)(0/)) - M(Xi(c)(0)) have been measured to be 107.8 +/- 1.7 +/- 2.5 and 107.0 +/- 1.4 +/- 2.5 MeV/c(2), respectively. [S0031-9007(98)08253-2].