We examine angular distributions of leptons arising from the decay of $J/\psi$ in inclusive hadroproduction. Taking into account feed-down contributions from ${\chi }_{1,2},$ a flat distribution emerges without fine tuning parameters. Changes in the ratio of direct to total $J/\psi$ cross sections would change this distribution significantly. Such angular distributions are, therefore, confirmatory tests of the $J/\psi$ suppression signal for the production of a quark-gluon plasma. Related effects are predicted for the ${\rm Y}.$

• Received 5 February 1998

DOI:https://doi.org/10.1103/PhysRevD.58.034006