A search for $CP$ violation with an entangled system of $\Xi^-\bar{\Xi}^+$ pairs is performed using $(10087 \pm 44)\times10^{6}$ $J/\psi$ events collected with the BESIII experiment. A nine-dimensional helicity amplitude is used to fit the process $e^+e^- \to J/\psi \to \Xi^-\bar{\Xi}^+$ and its subsequent decays. The $\Xi^-$ and $\bar{\Xi}^+$ decay parameters are determined with higher precision than the best results reported so far. Furthermore, the strong phase difference $$\delta_P-\delta_S = (0.3 \pm 1.2\,(\mathrm{stat}) \pm 0.2\,(\mathrm{syst})) \times 10^{-2}~\mathrm{rad},$$ and the weak phase difference $$\xi_P-\xi_S = (-0.2 \pm 1.2\,(\mathrm{stat}) \pm 0.1\,(\mathrm{syst})) \times 10^{-2}~\mathrm{rad},$$ are directly determined. These are the most precise measurements to date. The $CP$ asymmetry observables are determined to be $$A_{CP}^{\Xi} = (-7.8 \pm 4.8\,(\mathrm{stat}) \pm 0.8\,(\mathrm{syst})) \times 10^{-3}$$ and $$\Delta\phi_{CP}^{\Xi} = (0.6 \pm 5.1\,(\mathrm{stat}) \pm 0.2\,(\mathrm{syst})) \times 10^{-3}~\mathrm{rad},$$ both of which are consistent with $CP$ conservation. In addition, an independent measurement of the $\Lambda$ decay parameter and the $CP$ asymmetry $$A_{CP}^{\Lambda} = (-2.9 \pm 4.3\,(\mathrm{stat}) \pm 0.7\,(\mathrm{syst})) \times 10^{-3}$$ is obtained, in agreement with previous measurements but with substantially improved precision.

Precise Measurement of Matter-Antimatter Asymmetry with Entangled Hyperon-Antihyperon Pairs

Garzia, I.;Melendi, F.  M.;
2026

Abstract

A search for $CP$ violation with an entangled system of $\Xi^-\bar{\Xi}^+$ pairs is performed using $(10087 \pm 44)\times10^{6}$ $J/\psi$ events collected with the BESIII experiment. A nine-dimensional helicity amplitude is used to fit the process $e^+e^- \to J/\psi \to \Xi^-\bar{\Xi}^+$ and its subsequent decays. The $\Xi^-$ and $\bar{\Xi}^+$ decay parameters are determined with higher precision than the best results reported so far. Furthermore, the strong phase difference $$\delta_P-\delta_S = (0.3 \pm 1.2\,(\mathrm{stat}) \pm 0.2\,(\mathrm{syst})) \times 10^{-2}~\mathrm{rad},$$ and the weak phase difference $$\xi_P-\xi_S = (-0.2 \pm 1.2\,(\mathrm{stat}) \pm 0.1\,(\mathrm{syst})) \times 10^{-2}~\mathrm{rad},$$ are directly determined. These are the most precise measurements to date. The $CP$ asymmetry observables are determined to be $$A_{CP}^{\Xi} = (-7.8 \pm 4.8\,(\mathrm{stat}) \pm 0.8\,(\mathrm{syst})) \times 10^{-3}$$ and $$\Delta\phi_{CP}^{\Xi} = (0.6 \pm 5.1\,(\mathrm{stat}) \pm 0.2\,(\mathrm{syst})) \times 10^{-3}~\mathrm{rad},$$ both of which are consistent with $CP$ conservation. In addition, an independent measurement of the $\Lambda$ decay parameter and the $CP$ asymmetry $$A_{CP}^{\Lambda} = (-2.9 \pm 4.3\,(\mathrm{stat}) \pm 0.7\,(\mathrm{syst})) \times 10^{-3}$$ is obtained, in agreement with previous measurements but with substantially improved precision.
2026
Ablikim, M.; Achasov, M.  n.; Adlarson, P.; Ai, X.  c.; Aliberti, R.; Amoroso, A.; An, Q.; Bai, Y.; Bakina, O.; Ban, Y.; Bao, H. -R.; Bao, X.  l.; Bat...espandi
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11392/2634929
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