Hyperon polarization in Heavy-Ion Collisions and gravity-related anomaly

TL;DR

This paper investigates the energy dependence of hyperon polarization in heavy-ion collisions, highlighting the role of gravitational anomalies and axial vortical effects, and compares theoretical predictions with experimental data.

Contribution

It introduces a combined framework of kinetic models and anomaly effects to explain hyperon polarization, emphasizing gravitational anomaly contributions and their energy dependence.

Findings

Preliminary RHIC data align with suppression of gravitational anomaly effects.

Antihyperon polarization exceeds hyperon polarization, especially at lower energies.

Quadrupole structure of longitudinal vorticity is supported by helicity separation effects.

Abstract

We study the energy dependence of global polarization of $\Lambda$ hyperons in peripheral $Au-Au$ collisions. We combine the calculation of vorticity and strange chemical potential in the framework of kinetic Quark-Gluon String Model with the anomalous mechanism related to axial vortical effect. The earlier found effect of helicity separation implies the quadrupole structure of longitudinal vorticity. We pay special attention to the temperature dependent contribution related to gravitational anomaly and found that the preliminary RHIC data are compatible with its suppression discovered earlier in lattice calculations. The antihyperons polarization is excessing that of hyperons and the difference is more pronounced at smaller energies.