The J/ψ, ψ(3686)→Σ0Σ¯0 processes and subsequent decays are studied using the world’s largest J/ψ and ψ(3686) data samples collected with the BESIII detector. The parity-violating decay parameters of the decays Σ0→Λγ and Σ¯0→Λ¯γ, αΣ0=−0.0017±0.0021±0.0018 and α¯Σ0=0.0021±0.0020±0.0022, are measured for the first time. The strong CP symmetry is tested in the decays of the Σ0 hyperons for the first time by measuring the asymmetry ACPΣ=αΣ0+α¯Σ0=(0.4±2.9±1.3)×10−3. The weak CP test is performed in the subsequent decays of their daughter particles Λ and Λ¯. Also for the first time, the transverse polarizations of the Σ0 hyperons in J/ψ and ψ(3686) decays are observed with opposite directions, and the ratios between the S-wave and D-wave contributions of the J/ψ, ψ(3686)→Σ0Σ¯0 decays are obtained. These results are crucial to understand the decay dynamics of the charmonium states and the production mechanism of the Σ0−Σ¯0 pairs.
Published by the American Physical Society
2024