https://indico.ihep.ac.cn//event/11570/ https://www.nature.com/articles/s41567-019-0494-8

This Paper JC-139 is about Baryon Polarization and Entanglement in Baryon-Antibaryon Pair Production in Electron-Positron Annihilation.

Using a sample of 1.31x10^9 J/ψ events collected with BESIII detector, the first observation of spin polarization of Lambda and bar_Lambda hyperons from the coherent production in the J/ψ->ΛΛ̄ decay has been observed. They measured phase between the hadronic form factors to be ∆Φ=(42.4±0.6 ± 0.5). The decay parameters for Λ →pπ^- (α_-), Λ̄ → p̄π^+ (α_+) and Λ̄ → n̄π^0 ( ᾱ_0 ) are measured to be α_− = (0.750 ± 0.009 ± 0.004), α_+ = (−0.758 ± 0.010 ± 0.007) and ᾱ_0 = (−0.692 ± 0.016 ± 0.006), respectively. The obtained value of α_− is higher by (17 ± 3)% than the current world average. The ratio ᾱ_0 /α_+ = (0.913 ± 0.028 ± 0.012) is also measured.