Bulk viscosity-driven freeze-out in heavy ion collisions

TL;DR

This paper reviews the HBT puzzle in heavy ion collisions and proposes that a peak in bulk viscosity near the phase transition causes system fragmentation and freeze-out, offering a new physics explanation.

Contribution

It introduces the idea that a bulk viscosity peak near the phase transition can induce instability and fragmentation, providing a novel mechanism for freeze-out in heavy ion collisions.

Findings

Bulk viscosity peaks near the phase transition.

Viscosity peak can cause system instability.

Fragmentation leads to freeze-out independent of system size.

Abstract

We give an review the HBT puzzle, and argue that its resolution requires the introduction of new physics close to the phase transition scale. We argue that a candidate for this new physics is bulk viscosity, recently postulated to peak, and even diverge, close to the phase transition temperature. We show that such a viscosity peak can force the system created in heavy ion collisions to become unstable, and filament into fragments whose size is weakly dependent on the global size of the system, thereby triggering freeze-out.