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

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 ${\lambda }_{\varphi }$ were obtained. The study was performed in the kinematic region 2.5<y<4, 2<$p_{\mathrm{T}}$<8 GeV/$c$, in the helicity and Collins-Soper reference frames. In both frames, the polarization parameters are compatible with zero, within uncertainties.