Transverse and longitudinal spin alignment from color fields in heavy ion collisions

TL;DR

This paper investigates how color fields in heavy ion collisions influence the spin alignment of vector mesons, proposing that measuring longitudinal spin alignment can reveal the dominance of glasma-induced spin correlations.

Contribution

It extends the quark-coalescence model to relativistic cases and analyzes spin alignment from color fields, highlighting the potential of longitudinal spin measurements to identify glasma effects.

Findings

Spin alignment from glasma fields shows momentum dependence.

Longitudinal spin alignment can indicate glasma dominance.

Qualitative analysis of isotropic color fields in QGP phase.

Abstract

We analyze the spin alignment of vector mesons stemming from spin correlation of the quark and antiquark induced by background color fields in relativistic heavy ion collisions. The quark-coalescence equation relating the collision kernel of the vector-meson kinetic equation to spin alignment is expanded to the relativistic case. Focusing on the color-octet contribution, the spin alignment for $\phi$ mesons from glasma fields with momentum dependence is investigated, where the scenarios for different spin quantization axes are considered. Moreover, we qualitatively analyze the spin alignment from isotropic color fields in the quark gluon plasma phase for comparison. In particular, we propose that the experimental measurement of spin alignment along the beam direction, dubbed as the longitudinal spin alignment, could be useful to identify the dominance of longitudinal spin correlation potentially led by the glasma effect in high-energy nuclear collisions.