J/Psi Polarization in 800-GeV p-Cu Interactions

TL;DR

This paper reports measurements of J/psi polarization in 800-GeV proton-copper interactions, revealing polarization dependence on Feynman-x but not on transverse momentum, providing insights into charm quark production and hadronization.

Contribution

First measurement of J/psi polarization in high-energy proton-nucleus interactions across a range of kinematic variables.

Findings

Longitudinal polarization at large x_F

Unpolarized or slightly transverse at small x_F

No significant polarization variation with p_T

Abstract

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 \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} $.