Strong and Weak CP Tests in Sequential Decays of Polarized ς0 Hyperons

Abstract

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.