Model-Independent Determination of the Spin of the Ω− and Its Polarization Alignment in ψ(3686)→Ω−Ω¯+

Abstract

We present an analysis of the process $\psi (3686)\to {\mathrm{\Omega }}^{-}{\overline{\mathrm{\Omega }}}^{+}$ (${\mathrm{\Omega }}^{-}\to K^{-}\mathrm{\Lambda }$, ${\overline{\mathrm{\Omega }}}^{+}\to K^{+}\overline{\mathrm{\Lambda }}$, $\mathrm{\Lambda }\to p{\pi }^{-}$, $\overline{\mathrm{\Lambda }}\to \overline{p}{\pi }^{+}$) based on a dataset of $448\times {10}^6\psi (3686)$ decays collected with the BESIII detector at the BEPCII electron-positron collider. The helicity amplitudes for the process $\psi (3686)\to {\mathrm{\Omega }}^{-}{\overline{\mathrm{\Omega }}}^{+}$ and the decay parameters of the subsequent decay ${\mathrm{\Omega }}^{-}\to K^{-}\mathrm{\Lambda }$ $({\overline{\mathrm{\Omega }}}^{+}\to K^{+}\overline{\mathrm{\Lambda }})$ are measured for the first time by a fit to the angular distribution of the complete decay chain, and the spin of the ${\mathrm{\Omega }}^{-}$ is determined to be $3/2$ for the first time since its discovery more than 50 years ago.