Quarkonium polarization in heavy ion collisions as a possible signature of the quark--gluon plasma

Abstract

The polarization of quarkonium states produced in hadron collisions exhibits strong non-perturbative effects - for example, at small transverse momentum $p_t$ charmonia appear unpolarized, in sharp contradiction to the predictions of perturbation theory. The quark--gluon plasma is expected to screen away the non-perturbative physics; therefore those quarkonia which escape from the plasma should possess polarization as predicted by perturbative QCD. We estimate the expected $J/\psi$ polarization at small $p_t$, and find that it translates into the asymmetry of the $e^{+}{e}^{-}({\mu }^{+}{\mu }^{-})$ angular distribution $W(\theta )\sim 1+\alpha co{s}^2\theta$, with $\alpha \simeq 0.35÷0.4$.

4 pages, no figures

References in corpus (1)

• J/Psi -> ee and J/Psi -> μμMeasurements in AuAu and pp Collisions at sqrt{s_{NN}} = 200 GeV

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• QCD corrections to J/psi polarisation in pp collisions at RHIC
• Quarkonium Physics at a Fixed-Target Experiment using the LHC Beams
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• First measurement of quarkonium polarization in nuclear collisions at the LHC
• Prospects for quarkonium studies at the high-luminosity LHC
• J/$\psi$ production in In-In and p-A collisions
• Polarization of Lambda^0 hyperons in nucleus-nucleus collisions at high energies
• Quarkonia measurements with ALICE at the LHC
• Quarkonium production: An experimental overview
• Heavy-Flavor Measurements by the PHENIX Experiment at RHIC