Strong and Weak CP Tests in Sequential Decays of Polarized Σ^{0} Hyperons

Area of Science:

• Particle Physics
• Quantum Chromodynamics
• Hadron Spectroscopy

Background:

• The J/ψ and ψ(3686) charmonium states are crucial for understanding strong interactions.
• The decays of these states provide a rich environment for studying fundamental symmetries.

Purpose of the Study:

• To investigate the J/ψ and ψ(3686)→Σ⁰Σ̅⁰ processes and subsequent decays.
• To measure parity-violating decay parameters and test CP symmetry in Σ⁰ hyperon decays.
• To study the transverse polarization of Σ⁰ hyperons and their production mechanism.

Main Methods:

• Analysis of the world's largest J/ψ and ψ(3686) data samples collected by the BESIII detector.
• Measurement of decay parameters α_{Σ⁰} and α̅_{Σ⁰} for Σ⁰→Λγ and Σ̅⁰→Λ̅γ decays.
• Determination of the CP-violating asymmetry A_{CP}^{Σ} and analysis of transverse polarizations.

Main Results:

• First measurements of parity-violating decay parameters for Σ⁰→Λγ and Σ̅⁰→Λ̅γ.
• First test of strong CP symmetry in Σ⁰ hyperon decays, yielding A_{CP}^{Σ}=(0.4±2.9±1.3)×10⁻³.
• Observation of transverse polarizations of Σ⁰ hyperons in J/ψ and ψ(3686) decays with opposite directions.
• Extraction of S-wave and D-wave contributions to J/ψ, ψ(3686)→Σ⁰Σ̅⁰ decays.

Conclusions:

• These findings offer crucial insights into the decay dynamics of charmonium states.
• The results contribute to a deeper understanding of the Σ⁰-Σ̅⁰ pair production mechanism.
• The study advances the investigation of fundamental symmetries in particle physics.