Observation of Two Narrow States Decaying into ${\Xi }_c^{+}\gamma$ and ${\Xi }_c^0\gamma$

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 CESR. We interpret the observed signals as the ${\Xi }_c^{+\prime }(csu)$ and ${\Xi }_c^{0\prime }(csd)$, the symmetric partners of the well-established antisymmetric ${\Xi }_c^{+}(c[su])$ and ${\Xi }_c^0(c[sd])$. The mass differences $M({\Xi }_c^{+\prime })-M({\Xi }_c^{+})$ and $M({\Xi }_c^{0\prime })-M({\Xi }_c^0)$ are measured to be $107.8\pm 1.7\pm 2.5$ and $107.0\pm 1.4\pm 2.5MeV/c^2$, respectively.

11 pages, postscript file also available through http://w4.lns.cornell.edu/public/CLNS