First simultaneous measurement of ${\Xi }^0$ and ${\bar{\Xi }}^0$ asymmetry parameters in $\psi (3686)$ decay

Abstract

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

8 pages, 3 figures, 2 tables, consistent with paper published in Phys. Rev. D (Letter) 108, L011101(2023)

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• Precise Measurements of Decay Parameters and $CP$ Asymmetry with Entangled $\Lambda -\bar{\Lambda }$ Pairs
• ${\Sigma }^{+}$ and ${\bar{\Sigma }}^{-}$ polarization in the $J/\psi$ and $\psi (3686)$ decays
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• A fast simulation package for STCF detector
• Observation of $\psi (3686)\to \Xi (1530{)}^0\bar{\Xi }(1530{)}^0$ and $\Xi (1530{)}^0{\bar{\Xi }}^0$
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Cited by in corpus (9)

• Tests of $CP$ symmetry in the entangled ${\Xi }^0-{\bar{\Xi }}^0$ Pairs
• Strong and weak $CP$ tests in sequential decays of polarized ${\Sigma }^0$ hyperons
• Measurement of the cross section of $e^{+}{e}^{-}\to {\Xi }^{-}{\bar{\Xi }}^{+}$ at center-of-mass energies between 3.510 and 4.843 GeV
• Production and decay of hyperons in a transversely polarized electron-positron collider
• The electromagnetic form factors and spin polarization of ${\Lambda }_c^{+}$ in the process $e^{+}{e}^{-}\to {\Lambda }_c^{+}{\bar{\Lambda }}_c^{-}$
• Measurement of Born cross section of $e^{+}{e}^{-}\to {\Sigma }^0{\bar{\Sigma }}^0$ at $\sqrt{s}=3.50-4.95$ GeV
• Tests of CP symmetry in entangled hyperon anti-hyperon pairs at BESIII
• Observation of Transverse Polarization and Determination of Psionic Form Factors of the $\Lambda$ Hyperon at $\sqrt{s}=3.773$ GeV
• Observation of $\Xi (1530{)}^0$ Polarization and Determination of Its Electric and Magnetic Moments in $\psi (3686)\to \Xi (1530{)}^0\bar{\Xi }(1530{)}^0$