Spin polarization for massive fermion in a shear flow: complete results at $O(\partial)$

TL;DR

This paper provides a comprehensive analysis of spin polarization of massive fermions in a shear flow within a QED plasma, revealing collision-independent effects and potential enhancements relevant to heavy ion collision experiments.

Contribution

It introduces a complete calculation including collision-dependent and independent contributions to fermion spin polarization in shear flow, extending previous free theory results.

Findings

Collision dependencies cancel out in final results

Shear flow can significantly enhance spin polarization

Results are relevant for understanding hyperon polarization in heavy ion collisions

Abstract

Motivated by the key role of shear induced polarization in understanding the local spin polarization puzzle of $\Lambda$ hyperons in heavy ion collisions, we perform a complete analysis of spin polarization of massive fermion in a quantum electrodynamic plasma with shear flow. Apart from the well-known spin-shear coupling in free theory, we include two more collision dependent contributions: one is a non-dynamical contribution fixed by shifted spin-averaged distribution in steady state; the other is a dynamical contribution following from spin evolution. Despite of the dependencies on collision, we find the dependencies on coupling drop out in the final results. These contributions can lead to significant enhancement of the spin-shear coupling in phenomenologically interesting regime.