Measurements of ${\Lambda }_c^{+}$ branching fractions of Cabibbo-suppressed decay modes involving $\Lambda$ and ${\Sigma }^0$

We measure the branching ratios of the Cabibbo-suppressed decays ${\Lambda }_c^{+}\to \Lambda K^{+}$ and ${\Lambda }_c^{+}\to {\Sigma }^0{K}^{+}$ relative to the Cabibbo-favored decay modes ${\Lambda }_c^{+}\to \Lambda {\pi }^{+}$ and ${\Lambda }_c^{+}\to {\Sigma }^0{\pi }^{+}$ to be $0.044\pm 0.004(\mathrm{stat}.)\pm 0.003(\mathrm{syst}.)$ and $0.038\pm 0.005(\mathrm{stat}.)\pm 0.003(\mathrm{syst}.)$, respectively. We set an upper limit on the branching ratio at the 90% confidence level for ${\Lambda }_c^{+}\to \Lambda K^{+}{\pi }^{+}{\pi }^{-}$ of $4.1\times {10}^{-2}$ relative to ${\Lambda }_c^{+}\to \Lambda {\pi }^{+}$, and for ${\Lambda }_c^{+}\to {\Sigma }^0{K}^{+}{\pi }^{+}{\pi }^{-}$ of $2.0\times {10}^{-2}$ relative to ${\Lambda }_c^{+}\to {\Sigma }^0{\pi }^{+}$. We also measure the branching fraction for the Cabibbo-favored mode ${\Lambda }_c^{+}\to {\Sigma }^0{\pi }^{+}$ relative to ${\Lambda }_c^{+}\to \Lambda {\pi }^{+}$ to be $0.977\pm 0.015(\mathrm{stat}.)\pm 0.051(\mathrm{syst}.)$. This analysis was performed using a data sample with an integrated luminosity of $125{\mathrm{fb}}^{-1}$ collected by the $BABAR$ detector at the PEP-II asymmetric-energy $B$ factory at SLAC.

Figure 1

The invariant mass of $p{\pi }^{-}$ combinations. The solid line indicates the result of the fit for the sum of the signal and background and the dashed line for the background only.

Figure 2

The distribution of the invariant mass difference between $\gamma p{\pi }^{-}$ combinations and $p{\pi }^{-}$ candidates. The solid line indicates the result of the fit for the sum of the signal and background and the dashed line for the background only.

Figure 3

The invariant mass of the $\Lambda K^{+}$ combinations for $x_p>$ 0.5. The solid line indicates the result of the fit for the sum of the signal and background and the dashed line for the background only.

Figure 4

The invariant mass of the $\Lambda {\pi }^{+}$ combinations for $x_p>$ 0.5. The solid line indicates the result of the fit for the sum of the signal and backgrounds and the dashed line for the combinatorial background. The dotted line indicates the broad region corresponds to ${\Lambda }_c^{+}\to {\Sigma }^0{\pi }^{+}$ with a missing $\gamma$ and the dashed-dotted line represents the region corresponding to ${\Xi }_c^{+}/{\Xi }_c^0$ reflection with missing ${\pi }^0/{\pi }^{-}$.

Figure 5

The invariant mass of ${\Sigma }^0(\Lambda \gamma )K^{+}$ combinations for $x_p>0.5$, where we do not replace the ${\Sigma }^0$ mass with the PDG value of the ${\Sigma }^0$ mass, as compared to what we have done for our final fit (shown in Fig. 6). The solid line indicates the result of the fit for the sum of the signal and background and the dashed line for the background only.

Figure 6

The invariant mass of ${\Sigma }^0(\Lambda \gamma )K^{+}$ combinations for $x_p>0.5$. The solid line indicates the result of the fit for the sum of the signal and background and the dashed line for the background only.

Figure 7

The invariant mass of ${\Sigma }^0(\Lambda \gamma ){\pi }^{+}$ combinations for $x_p>0.5$. The solid line indicates the result of the fit for the sum of the signal and background and the dashed line for the background only.

Figure 8

Combinatorial ${\Xi }^{-}(\Lambda {\pi }^{-})K^{+}{\pi }^{+}$ invariant mass distribution for $x_p>0.6$. The solid line indicates the result of the fit for the sum of the signal and background and the dashed line for the background only.

Figure 9

Combinatorial $\Lambda {\mathrm{K}}_{\mathrm{S}}^0({\pi }^{+}{\pi }^{-})K^{+}$ invariant mass distribution for $x_p>0.6$. The solid line indicates the result of the fit for the sum of the signal and background and the dashed line for the background only.

Figure 10

The invariant mass of $\Lambda K^{+}{\pi }^{+}{\pi }^{-}$ combinations for $x_p>0.6$. The solid line indicates the result of the fit for the sum of the signal and background.

Figure 11

The invariant mass of ${\Sigma }^0(\Lambda \gamma )K^{+}{\pi }^{+}{\pi }^{-}$ combinations for $x_p>0.6$. The solid line indicates the result of the fit for the sum of the signal and background.