Measurement of Branching Fractions of Singly Cabibbo-suppressed Decays $\Lambda_c^+ \rightarrow \Sigma^{0} K^+$ and $\Sigma^{+} K_{S}^0$

TL;DR

This study measures the branching fractions of two rare, singly Cabibbo-suppressed decays of the Lambda_c+ baryon using BESIII data, providing the first measurement for one of these decay modes.

Contribution

The paper reports the first measurement of the branching fraction for the decay $ ext{Lambda}_c^+ ightarrow ext{Sigma}^+ K_S^0$, and improves the precision of existing measurements for related decay modes.

Findings

Branching fraction of $ ext{Lambda}_c^+ ightarrow ext{Sigma}^0 K^+$ is approximately $4.7 imes 10^{-4}$.

Branching fraction of $ ext{Lambda}_c^+ ightarrow ext{Sigma}^+ K_S^0$ is approximately $4.8 imes 10^{-4}$.

First measurement of the $ ext{Lambda}_c^+ ightarrow ext{Sigma}^+ K_S^0$ decay branching fraction.

Abstract

Based on a sample of 4.4 $\mathrm{fb}^{-1}$ of $e^{+}e^{-}$ annihilation data collected in the energy region between 4.6 GeV and 4.7 GeV with the BESIII detector at BEPCII, two singly Cabibbo-suppressed decays $\Lambda_c^+ \rightarrow \Sigma^0 K^+$ and $\Lambda_{c}^{+} \rightarrow \Sigma^+ K_{S}^0$ are studied. The ratio of the branching fraction $\mathcal{B}(\Lambda_c^+ \rightarrow \Sigma^0 K^+)$ relative to $\mathcal{B}(\Lambda_c^+ \rightarrow \Sigma^0 \pi^+)$ is measured to be $0.0361 \pm 0.0073(\mathrm{stat.}) \pm 0.0005(\mathrm{syst.})$, and the ratio of $\mathcal{B}(\Lambda_c^+ \rightarrow \Sigma^+ K_{S}^0)$ relative to $\mathcal{B}(\Lambda_{c}^{+} \rightarrow \Sigma^+ \pi^+ \pi^-)$ is measured to be $0.0106 \pm 0.0031(\mathrm{stat.}) \pm 0.0004(\mathrm{syst.})$. After taking the world-average branching fractions of the reference decay channels, the branching fractions $\mathcal{B}(\Lambda_c^+ \rightarrow \Sigma^0 K^+)$ and $\mathcal{B}(\Lambda_{c}^{+} \rightarrow \Sigma^+ K_{S}^0)$ are determined to be $(4.7\pm 0.9(\mathrm{stat.})\pm 0.1(\mathrm{syst.}) \pm 0.3(\mathrm{ref.}))\times10^{-4}$ and $(4.8\pm 1.4(\mathrm{stat.})\pm 0.2(\mathrm{syst.}) \pm 0.3(\mathrm{ref.}))\times10^{-4}$, respectively. The branching fraction of the $\Lambda_{c}^{+} \rightarrow \Sigma^+ K_{S}^0$ decay is measured for the first time.