# Nuclear jets in heavy-ion collisions recall a stream of sand

## TL;DR

This paper investigates the formation of nuclear jets in heavy-ion collisions, revealing that out-of-equilibrium dynamical instabilities can produce stable, sand-like cluster streams without cohesive forces, a phenomenon previously overlooked.

## Contribution

It introduces a novel dynamical modeling approach using the Boltzmann-Langevin equation to describe out-of-equilibrium nuclear jet formation and explores the interplay of surface and volume instabilities.

## Key findings

- Stable streaming clusters form from dynamical instabilities.
- Clusters resemble dry sand flow, not driven by cohesion.
- Out-of-equilibrium effects are crucial for jet formation.

## Abstract

Head-on collisions between nuclei of different size at Fermi energies may give rise to extremely deformed dynamical regimes and patterns. Those latter, may suddenly turn into a stream of nuclear clusters, resembling collimated jets. Because the underlying instabilities are inadequately described by usual modelling approaches based on equilibrium approximations, this mechanism resulted rather unnoticed, even though it should be frequently registered in experiments. We employ the Boltzmann-Langevin equation to specifically address out-of-equilibrium conditions and handle dynamical fluctuations. An interesting interplay between surface and volume instabilities is discussed for the first time. Stable and rather regular patterns of streaming clusters arise from these conditions. Counterintuitively, we find that these clustered structures are not triggered by cohesive forces and they recall the granular flow of a stream of dry sand.