We have measured branching ratios for three ${\mathrm{\Lambda }}_{\mathit{c}}$ decay modes that have a ${\mathrm{\Sigma }}^{+}$ in the final state. Two of the observed decay modes, ${\mathrm{\Lambda }}_{\mathit{c}}$→${\mathrm{\Sigma }}^{+}$${\mathrm{\pi }}^0$ and ${\mathrm{\Lambda }}_{\mathit{c}}^{+}$→${\mathrm{\Sigma }}^{+}$ω, have no external W-emission amplitudes. Their branching ratios relative to the ${\mathit{pK}}^{\mathrm{-}}$${\mathrm{\pi }}^{+}$ mode are 0.20±0.03±0.03 and 0.54±0.13±0.06, respectively. We have also significantly improved the measurement of the branching ratio for the previously observed decay mode ${\mathrm{\Lambda }}_{\mathit{c}}^{+}$→${\mathrm{\Sigma }}^{+}$${\mathrm{\pi }}^{+}$${\mathrm{\pi }}^{\mathrm{-}}$. We find its branching ratio relative to ${\mathit{pK}}^{\mathrm{-}}$${\mathrm{\pi }}^{+}$ to be 0.74±0.07±0.09.

• Received 24 June 1993

DOI:https://doi.org/10.1103/PhysRevLett.71.3255