Measurements of ${\Lambda }_c^{+}$ Branching Fractions of Cabibbo-Suppressed Decay Modes

Abstract

We have measured the branching fractions of the Cabibbo-suppressed decays ${\Lambda }_c^{+}$ $\to$ ${\Lambda }^0$ $K^{+}$ and ${\Lambda }_c^{+}$ $\to$ ${\Sigma }^0$ $K^{+}$ %(measured with improved accuracy). relative to the Cabibbo-allowed decay modes ${\Lambda }_c^{+}$ $\to$ ${\Lambda }^0$ ${\pi }^{+}$ and ${\Lambda }_c^{+}$ $\to$ ${\Sigma }^0$ ${\pi }^{+}$ to be $0.044\pm 0.004(\text{stat.})\pm 0.002(\text{syst.})$ and $0.040\pm 0.005(\text{stat.})\pm 0.004(\text{syst.})$, respectively. We also present the first observation of ${\Lambda }_c^{+}$ $\to$ ${\Lambda }^0$ $K^{+}{\pi }^{+}{\pi }^{-}$ and have measured the branching fraction relative to ${\Lambda }_c^{+}$ $\to$ ${\Lambda }^0$ ${\pi }^{+}$ to be $0.266\pm 0.027(\text{stat.})\pm 0.032(\text{syst.})$. The upper limit of the branching fraction into the decay ${\Lambda }_c^{+}$ $\to$ ${\Sigma }^0$ $K^{+}{\pi }^{+}{\pi }^{-}$ relative to ${\Lambda }_c^{+}$ $\to$ ${\Sigma }^0$ ${\pi }^{+}$ has been measured to be %7.6 \times 10^{-4} < 3.9 \times 10^{-2}$atthe90$^{-1}$ (integrated luminosity) collected by the \babar$ $detectoratthePEP-IIasymmetric-energy$B$ Factory at the Stanford Linear Accelerator Center. All results presented in this conference contribution are preliminary.

arXiv comment16pages, 5figures, contributed to ICHEP2004