Using $e^{+}{e}^{-}\to {\mathrm{\Lambda }}_c^{+}{\overline{\mathrm{\Lambda }}}_c^{-}$ production from a $567{\mathrm{pb}}^{-1}$ data sample collected by BESIII at 4.6 GeV, a full angular analysis is carried out simultaneously on the four decay modes of ${\mathrm{\Lambda }}_c^{+}\to p{K}_S^0$, $\mathrm{\Lambda }{\pi }^{+}$, ${\mathrm{\Sigma }}^{+}{\pi }^0$, and ${\mathrm{\Sigma }}^0{\pi }^{+}$. For the first time, the ${\mathrm{\Lambda }}_c^{+}$ transverse polarization is studied in unpolarized $e^{+}{e}^{-}$ collisions, where a nonzero effect is observed with a statistical significance of $2.1\sigma$. The decay asymmetry parameters of the ${\mathrm{\Lambda }}_c^{+}$ weak hadronic decays into $p{K}_S^0$, $\mathrm{\Lambda }{\pi }^{+}$, ${\mathrm{\Sigma }}^{+}{\pi }^0$ and ${\mathrm{\Sigma }}^0{\pi }^{+}$ 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 $\mathrm{\Lambda }{\pi }^{+}$ and ${\mathrm{\Sigma }}^{+}{\pi }^0$ modes are consistent but with improved precision, while the parameters for the $p{K}_S^0$ and ${\mathrm{\Sigma }}^0{\pi }^{+}$ modes are measured for the first time.

• Received 10 May 2019

DOI:https://doi.org/10.1103/PhysRevD.100.072004

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Published by the American Physical Society