Measurement of the inclusive J/$\psi$ polarization at forward rapidity in pp collisions at $\sqrt{s}=8$ TeV

We report on the measurement of the inclusive J/$\psi$ polarization parameters in pp collisions at a center of mass energy $\sqrt{s}=8$ TeV with the ALICE detector at the LHC. The analysis is based on a data sample corresponding to an integrated luminosity of 1.23 pb${}^{-1}$. J/$\psi$ resonances are reconstructed in their di-muon decay channel in the rapidity interval $2.5<y<4.0$ and over the transverse-momentum interval $2 < p_{\rm T} < 15$GeV\mathrm{/}$c$\mathrm{.}Thethreepolarizationparameters($\lambda_\theta$,$\lambda_\varphi$,$\lambda_{\theta\varphi}$)aremeasuredasafunctionof$p_{\rm T}$ both in the helicity and Collins-Soper reference frames. The measured J/$\psi$ polarization parameters are found to be compatible with zero within uncertainties, contrary to expectations from all available predictions. The results are compared with the measurement in pp collisions at $\sqrt{s} = 7$ TeV.