First measurement of quarkonium polarization in nuclear collisions at the LHC

The polarization of inclusive J/$\psi$ and $\Upsilon(1{\rm S})$ produced in Pb-Pb collisions at $\sqrt{s_{\rm{NN}}}=5.02$ TeV the LHC is measured with ALICE detector. study carried out by reconstructing quarkonium through its decay to muon pairs rapidity region $2.5<y<4$ measuring polar azimuthal angular distributions muons. parameters $\lambda_{\theta}$, $\lambda_{\phi}$ $\lambda_{\theta\phi}$ are helicity Collins-Soper reference frames, transverse momentum interval $2<p_{\rm T}<10$ GeV/$c$ $p_{\rm T}<15$ for S})$, respectively. found be compatible zero, within a maximum about two standard deviations low T}$, both frames over whole T}$ range. values compared corresponding results obtained pp $\sqrt{s}=7$ 8 similar kinematic LHCb experiments. Although much larger uncertainties, production also consistent zero.