Vortex Rings in Event-by-Event Relativistic Heavy-Ion Collisions

TL;DR

This paper uses event-by-event simulations to study vortex-ring structures in relativistic heavy-ion collisions, linking flow velocity profiles to hyperon polarization and predicting observable effects across different collision energies and systems.

Contribution

It introduces detailed modeling of vortex-ring formation in heavy-ion collisions and predicts measurable polarization signals related to these vortical structures.

Findings

Vortex-ring structures are formed in the longitudinal flow velocity profile.

Hyperon polarization can serve as a probe for vortex-ring features.

Predictions are made for future experimental verification at LHCb.

Abstract

We present event-by-event simulations for central asymmetric light+heavy and Au+Au collisions to investigate the formation and evolution of vortex-ring structures in the longitudinal flow velocity profile. The production-plane polarization of $\Lambda$ hyperons, defined w.r.t. the $\Lambda$ momentum and the beam, can track the "vortex-ring" feature in the event, a characteristic vortical structure generated by longitudinal flow gradients. We make comprehensive model predictions for the rapidity-dependent vortex-ring observables for different collision system sizes at $\sqrt{s_\mathrm{NN}} = 200$ and 72 GeV. Our predictions at the latter energy can be explored in the future LHCb fixed-target experiment at the Large Hadron Collider.