J/ψPolarization in 800-GeVp−CuInteractions

We present measurements of the polarization of the $J/\psi$ produced in 800-GeV proton interactions with a copper target. Polarization of the $J/\psi$ is sensitive to the $c\overline{c}$ production and hadronization processes. A longitudinal polarization is observed at large $x_F$, while at small $x_F$ the state is produced essentially unpolarized or slightly transversely polarized. No significant variation of the polarization is observed versus $p_T$.