J/$\psi$ polarization in pp collisions at $\sqrt{s}=7$ TeV

TL;DR

This paper measures the polarization of J/psi particles produced in proton-proton collisions at 7 TeV, finding results consistent with no polarization within experimental uncertainties.

Contribution

It provides the first detailed measurement of J/psi polarization parameters in the specified kinematic range at the LHC.

Findings

J/psi polarization parameters are compatible with zero.

Results are consistent across different reference frames.

No significant polarization observed within uncertainties.

Abstract

We have studied J/psi production in pp collisions at $\sqrt{s}=7$ TeV at the LHC through its muon pair decay. The polar and azimuthal angle distributions of the decay muons were measured, and results on the J/$\psi$ polarization parameters $\lambda_{\theta}$ and $\lambda_\phi$ were obtained. The study was performed in the kinematic region 2.5<y<4, 2<$p_{\rm T}$<8 GeV/$c$, in the helicity and Collins-Soper reference frames. In both frames, the polarization parameters are compatible with zero, within uncertainties.