Bulk Viscosity driven clusterization of quark-gluon plasma and early freeze-out in relativistic heavy-ion collisions

TL;DR

This paper proposes that increased bulk viscosity near hadronization causes quark-gluon plasma to fragment into clusters, potentially resolving the HBT puzzle by explaining early freeze-out and particle emission patterns.

Contribution

It introduces a novel clustering scenario driven by bulk viscosity effects, offering a new perspective on the dynamics of quark-gluon plasma in heavy-ion collisions.

Findings

Clusters are smaller and independent of total system volume.

Clusters preserve initial flow but do not develop new flow.

The model provides a new explanation for early freeze-out phenomena.

Abstract

We introduce a new scenario for heavy ion collisions that could solve the lingering problems associated with the so-called HBT puzzle. We postulate that the system starts expansion as the perfect quark-gluon fluid but close to freeze-out it splits into clusters, due to a sharp rise of bulk viscosity in the vicinity of the hadronization transition. We then argue that the characteristic cluster size is determined by the viscosity coefficient and the expansion rate. Typically it is much smaller and independent of the total system volume. These clusters maintain the pre-existing outward-going flow, as a spray of droplets, but develop no flow of their own, and hadronize by evaporation. We provide an ansatz for converting the hydrodynamic output into clusters.