Spin alignment of quarkonia in vortical quark-gluon plasma*

Abstract The spin alignment of with respect to the event plane in relativistic heavy ion collisions exhibits a significant signal. We propose a possible mechanism for spin alignment through the spin-dependent dissociation of quarkonia in vortical quark-gluon plasma. The spin-dependent dissociation is realized through inelastic scattering between constituents of quarkonium and those of quark-gluon plasma polarized by vorticity. The spin-dependent dissociation rate is found to depend on the directions of vorticity, quantization axis, and quark momentum. We implement our results in a dissociation-dominated evolution model for quarkonia in the Bjorken flow, finding that the spin 0 state is slightly suppressed compared with the average of the other two, which is consistent with the sign observed in experiments. We also observe the absence of logarithmic enhancement in the binding energy in the vortical correction to the dissociation rate, which is understood from the requirement that a spin-dependent dissociation can only result from quark coupling to a pair of chromomagnetic and chromoelectric fields.