A team of scientists from the RIKEN Nishina Center for Accelerator-Based Science, Tokyo Institute of Technology, and Kyoto University has discovered a new driver that controls the rapid shape changes of tiny drops of quark-gluon plasma (QGP) created in ultrarelativistic heavy-ion collisions.

QGP is matter in a state that is believed to have existed in the early universe microseconds after the Big Bang. By recreating QGP in high-energy collisions of heavy ions like gold and lead, scientists can study the properties and behavior of this exotic matter.

When QGP is produced in a collision, it expands rapidly and forms a tiny liquid droplet. The collisions create a strong force called hydrodynamic pressure that drives the expansion and causes the droplet to deform into various shapes. The shapes of these droplets can provide valuable insights into the properties of QGP.

In this study, the scientists discovered that the amount of shear viscosity, a property of QGP that represents its resistance to flow, plays a crucial role in determining the shape of the droplet.

They found that droplets with lower shear viscosity deform into more elongated and unstable shapes, while droplets with higher shear viscosity tend to maintain a spherical shape.

This finding suggests that the interplay of hydrodynamic pressure and shear viscosity is a key factor in controlling the rapid shape changes of QGP droplets.

The scientists believe that the new driver identified in this study will provide a better understanding of the properties of QGP and help scientists further probe the early universe.