Measurements of Weak Decay Asymmetries of ${\Lambda }_c^{+}\to p{K}_S^0$, $\Lambda {\pi }^{+}$, ${\Sigma }^{+}{\pi }^0$, and ${\Sigma }^0{\pi }^{+}$

Abstract

Using $e^{+}{e}^{-}\to {\Lambda }_c^{+}{\bar{\Lambda }}_c^{-}$ production from a 567 pb${}^{-1}$ data sample collected by BESIII at 4.6 GeV, a full angular analysis is carried out simultaneously on the four decay modes of ${\Lambda }_c^{+}\to p{K}_S^0$, $\Lambda {\pi }^{+}$, ${\Sigma }^{+}{\pi }^0$, and ${\Sigma }^0{\pi }^{+}$. For the first time, the ${\Lambda }_c^{+}$ transverse polarization is studied in unpolarized $e^{+}{e}^{-}$ collisions, where a non-zero effect is observed with a statistical significance of 2.1$\sigma$. The decay asymmetry parameters of the ${\Lambda }_c^{+}$ weak hadronic decays into $p{K}_S^0$, $\Lambda {\pi }^{+}$, ${\Sigma }^{+}{\pi }^0$ and ${\Sigma }^0{\pi }^{+}$ are measured to be $0.18\pm 0.43(\mathrm{stat})\pm 0.14(\mathrm{syst})$, $-0.80\pm 0.11(\mathrm{stat})\pm 0.02(\mathrm{syst})$, $-0.57\pm 0.10(\mathrm{stat})\pm 0.07(\mathrm{syst})$, and $-0.73\pm 0.17(\mathrm{stat})\pm 0.07(\mathrm{syst})$, respectively. In comparison with previous results, the measurements for the $\Lambda {\pi }^{+}$ and ${\Sigma }^{+}{\pi }^0$ modes are consistent but with improved precision, while the parameters for the $p{K}_S^0$ and ${\Sigma }^0{\pi }^{+}$ modes are measured for the first time.