First simultaneous measurement of Ξ0 and Ξ¯0 asymmetry parameters in ψ(3686) decay

Résumé fourni par la source

The ${\mathrm{\ensuremath{\Xi}}}^{0}$ asymmetry parameters are measured using entangled quantum ${\mathrm{\ensuremath{\Xi}}}^{0}\ensuremath{-}{\overline{\mathrm{\ensuremath{\Xi}}}}^{0}$ pairs from a sample of $(448.1\ifmmode\pm\else\textpm\fi{}2.9)\ifmmode\times\else\texttimes\fi{}{10}^{6}\text{ }\text{ }\ensuremath{\psi}(3686)$ events collected with the BESIII detector at BEPCII. The relative phase between the transition amplitudes of the ${\mathrm{\ensuremath{\Xi}}}^{0}{\overline{\mathrm{\ensuremath{\Xi}}}}^{0}$ helicity states is measured to be $\mathrm{\ensuremath{\Delta}}\mathrm{\ensuremath{\Phi}}=\ensuremath{-}0.050\ifmmode\pm\else\textpm\fi{}\phantom{\rule{0ex}{0ex}}0.150\ifmmode\pm\else\textpm\fi{}0.020\text{ }\text{ }\mathrm{rad}$, which implies that there is no obvious polarization at the current level of statistics. The decay parameters of the ${\mathrm{\ensuremath{\Xi}}}^{0}$ hyperon $({\ensuremath{\alpha}}_{{\mathrm{\ensuremath{\Xi}}}^{0}},{\ensuremath{\alpha}}_{{\overline{\mathrm{\ensuremath{\Xi}}}}^{0}},{\ensuremath{\phi}}_{{\mathrm{\ensuremath{\Xi}}}^{0}},{\ensuremath{\phi}}_{{\overline{\mathrm{\ensuremath{\Xi}}}}^{0}})$ and the angular distribution parameter $[{\ensuremath{\alpha}}_{\ensuremath{\psi}(3686)}]$ and $\mathrm{\ensuremath{\Delta}}\mathrm{\ensuremath{\Phi}}$ are measured simultaneously for the first time. In addition, the $CP$ asymmetry observables are determined to be ${A}_{CP}^{{\mathrm{\ensuremath{\Xi}}}^{0}}=({\ensuremath{\alpha}}_{{\mathrm{\ensuremath{\Xi}}}^{0}}+{\ensuremath{\alpha}}_{{\overline{\mathrm{\ensuremath{\Xi}}}}^{0}})/({\ensuremath{\alpha}}_{{\mathrm{\ensuremath{\Xi}}}^{0}}\ensuremath{-}{\ensuremath{\alpha}}_{{\overline{\mathrm{\ensuremath{\Xi}}}}^{0}})=\ensuremath{-}0.007\ifmmode\pm\else\textpm\fi{}0.082\ifmmode\pm\else\textpm\fi{}0.025$ and $\mathrm{\ensuremath{\Delta}}{\ensuremath{\phi}}_{CP}^{{\mathrm{\ensuremath{\Xi}}}^{0}}=({\ensuremath{\phi}}_{{\mathrm{\ensuremath{\Xi}}}^{0}}+{\ensuremath{\phi}}_{{\overline{\mathrm{\ensuremath{\Xi}}}}^{0}})/2=\ensuremath{-}0.079\ifmmode\pm\else\textpm\fi{}0.082\ifmmode\pm\else\textpm\fi{}0.010\text{ }\text{ }\mathrm{rad}$, which are consistent with $CP$ conservation.

Ce résumé expose les affirmations des auteurs. BNTIC ne l’interprète pas comme une validation indépendante des résultats.