Measurements of weak decay asymmetries of Λc+→pKs0, Λπ+, Σ+π0, and Σ0π+

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Abstract

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

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