Scientists from WITH For the first time, we have obtained direct evidence that quarks flying through quark-gluon plasma leave swirling trails behind them. This discovery confirms that the primordial soup of the early Universe behaved like a liquid, rather than a chaotic mixture of individual particles.
The results are published in the journal Physical letters.
The first moments of the universe
In the first microseconds after the Big Bang, space was filled with a hot mixture of quarks and gluons at temperatures of trillions of degrees. This “quark-gluon plasma” exists for an extremely short time before individual quarks and gluons combine into protons, neutrons, and other elementary particles that make up modern matter.
Physicists at CERN are recreating this primordial soup by colliding heavy ions at nearly the speed of light. Collisions create short-lived plasma droplets that can be inspected using detectors and complex algorithms.
“We are essentially taking a snapshot of how quarks interact with extreme liquids,” said Professor Yen-Ji Lee.
quark vortex
The team found that individual quarks flying through the plasma leave behind noticeable swirls, similar to the ripples created by a duck on the surface of water. This shows that the plasma reacts as a single fluid, slowing down the quarks and causing the energy to be distributed into waves and vortices.
To make the observations, physicists used a unique Z-boson approach. These neutral particles practically do not interact with the plasma, so any ripples or vortices are detected specifically behind the quark. The researchers analyzed about 13 billion collisions, from which they selected about 2,000 Z-boson events, allowing the effects of individual quarks to be observed without distorting other particles.
“When quarks move together with Z bosons, vortices form in the opposite direction, giving us a clear snapshot of the behavior of the primordial plasma,” Li explains.
Test the theory
Previous predictions about the liquid nature of quark-gluon plasma were part of a hybrid model by Professor Krishna Rajagopal at MIT. This theory holds that a quark passing through a dense plasma creates a visible trail behind it, causing particles to splash and ripple. The new results fully confirm these calculations.
“This is the long-awaited proof that physicists have been waiting for many years,” said Daniel Pablos from the University of Oviedo.
An important discovery of physics
Measuring the size, shape, and dissipation time of the vortices helps understand the internal properties of the quark-gluon plasma. Scientists can study its density, viscosity and particle interactions at extremely high temperatures, providing insight into the behavior of matter in the first microseconds of the Universe.
“We have obtained the first evidence that a quark drags plasma with it, creating visible vortices. This allows us to study the primordial soup as a true liquid, rather than a chaotic mixture of particles, and opens up new possibilities for understanding the early Universe,” Lee concluded.
