Polarized Dissociation and Spin Alignment of Moving Quarkonium in Quark-Gluon Plasma

TL;DR

This paper investigates how the spin alignment of quarkonium in quark-gluon plasma is affected by polarized dissociation mechanisms, providing a theoretical framework for understanding recent experimental observations.

Contribution

It introduces a polarized dissociation model for quarkonium in QGP using spin chromomagnetic coupling within potential NRQCD, including leading and next-to-leading order processes.

Findings

Spin 0 quarkonium states dissociate less than other spin states.

The model predicts a positive deviation of 0-1/3 in spin alignment.

Application to Bjorken flow suggests medium effects influence quarkonium spin states.

Abstract

Recent experiments have found spin alignment of $J/\psi$ with respect to event plane in heavy ion collisions, suggesting a medium effect that is spin dependent. We propose a possible mechanism with polarized dissociation from the motion of $J/\psi$ with respect to the medium. We calculate polarized dissociation rate for quarkonium spin triplet state from spin chromomagnetic coupling in the potential non-relativistic QCD framework. This is done for the leading order gluo-dissociation process and next to leading order inelastic Coulomb scattering process. The polarized dissociation rate is expressed as a function of relative velocity between quarkonium and QGP and the quantization axis. Applying the polarized dissociation rate to quarkonium evolution with dissociation effect only in a Bjorken flow, we find the spin $0$ state to dissociate less than the other spin states, leading to positive $\rho_{00}-1/3$. Regeneration contribution is expected to give a contribution with the opposite sign.