Model-Independent Determination of the Spin of the ω- And Its Polarization Alignment in ψ (3686) → ω-ω¯

We present an analysis of the process ψ(3686)→ω-ω¯+ (ω-→K-Λ, ω¯+→K+Λ¯, Λ→pπ-, Λ¯→p¯π+) based on a dataset of 448×106 ψ(3686) decays collected with the BESIII detector at the BEPCII electron-positron collider. The helicity amplitudes for the process ψ(3686)→ω-ω¯+ and the decay parameters of the subsequent decay ω-→K-Λ (ω¯+→K+Λ¯) are measured for the first time by a fit to the angular distribution of the complete decay chain, and the spin of the ω- is determined to be 3/2 for the first time since its discovery more than 50 years ago.