# Local spin polarization of $\Lambda$ hyperons and its interaction corrections

## TL;DR

This paper calculates the spin polarization of $\\Lambda$ hyperons in heavy-ion and proton-lead collisions using hydrodynamics, successfully matching Au+Au data but highlighting puzzles in p+Pb collisions, and discusses recent theoretical developments.

## Contribution

It introduces a hydrodynamic calculation of hyperon spin polarization and explores interaction corrections, addressing experimental data and theoretical advancements.

## Key findings

- Successfully describes Au+Au collision data
- Highlights unresolved issues in p+Pb collisions
- Discusses recent progress in quantum kinetic theory

## Abstract

We have computed the second Fourier sine coefficient of the longitudinal spin polarization, $\langle P_{z} \sin 2(\phi_{p} - \Psi_{2}) \rangle$, as a function of multiplicity or centrality in Au+Au collisions at $\sqrt{s_{NN}} = 200$ GeV and in $p$+Pb collisions at $\sqrt{s_{NN}} = 8.16$ TeV using the CLVisc hydrodynamic framework. The numerical results successfully describe the data in Au+Au collisions. However, understanding the data in $p$+Pb collisions remains a puzzle. Additionally, we have reported some recent developments in quantum kinetic theory and spin hydrodynamics.