Measurement of masses of the ${\Xi }_c(2645)$ and ${\Xi }_c(2815)$ baryons and observation of ${\Xi }_c(2980)\to {\Xi }_c(2645)\pi$ %and observation of the ${\Xi }_c(2980)$ and observation of ${\Xi }_c(2980)\to {\Xi }_c(2645)\pi$

Abstract

We report a precise measurement of the masses of the ${\Xi }_c(2645)$ and ${\Xi }_c(2815)$ baryons using a data sample of 414 fb${}^{-1}$ collected by the Belle collaboration at the KEKB $e^{+}{e}^{-}$ collider. The states ${\Xi }_c(2645{)}^{0,+}$ are observed in the ${\Xi }_c^{+,0}{\pi }^{-,+}$ decay modes, while the ${\Xi }_c(2815{)}^{0,+}$ are reconstructed in the ${\Xi }_c(2645{)}^{+,0}{\pi }^{-,+}$ decay modes. The following mass splittings are determined: $m_{{\Xi }_c(2645{)}^{+}}-m_{{\Xi }_c(2645{)}^0}=(-0.1\pm 0.3(\mathrm{stat})\pm 0.6(\mathrm{syst}))\mathrm{MeV}/{\mathrm{c}}^2$ and $m_{{\Xi }_c(2815{)}^{+}}-m_{{\Xi }_c(2815{)}^0}=(-3.4\pm 1.9(\mathrm{stat})\pm 0.9(\mathrm{syst}))\mathrm{MeV}/{\mathrm{c}}^2$ with a much better precision than the current world averages. We also observe a new decay mode, ${\Xi }_c(2980{)}^{0,+}\to {\Xi }_c(2645{)}^{+,0}{\pi }^{-,+}$.

13 pages, 4 figures, submitted to Phys. Lett. B