Polarized angular distributions in the decays of the ψ’ charmonium state directly produced in unpolarized proton–antiproton collisionsA.W.K. Mok and K.J. SebastianEur. Phys. J. C, 56 2 (2008) 189-202DOI: https://doi.org/10.1140/epjc/s10052-008-0649-8