2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/207300We present measurements of the polarization of the $ J/ψ$ produced in 800-GeV proton interactions with a copper target. Polarization of the $ J/ψ$ is sensitive to the $ c \bar{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} $.4 pages, 3 figuresHigh Energy Physics - Experimenttext