Vortex rings from high energy central p+A collisions

TL;DR

This paper models the formation of vortex rings in quark-gluon plasma produced in high-energy proton-nucleus collisions, proposing experimental methods to detect these structures and explore collectivity in small QGP droplets.

Contribution

It introduces viscous relativistic hydrodynamic simulations of ultra-central p+A collisions and proposes an observable to detect vortex toroids via hyperon polarization.

Findings

Vortex rings can form in small QGP droplets.

The proposed observable is robust against vorticity definition changes.

Experiments at RHIC and LHC can test for vortex structures.

Abstract

Relativistic p+A collisions may produce droplets of quark gluon plasma (QGP) that quickly develop a toroidal vortex structure similar to that of an expanding smoke ring. We present viscous relativistic hydrodynamic calculations of ultra-central p+A collisions and develop an experimental observable to probe the structure, correlating the polarization and momentum of hyperons emitted from the collision. The effect is robust against changes in the definition of vorticity used to calculate the polarization. Experiments at RHIC and LHC may test the existence and strength of the vortex toroids, bringing new evidence to bear on the question of collectivity in the smallest QGP droplets.