Supercomputers Reveal Transformation from Subatomic Soup to Today's Atoms

A subatomic soup filled our early universe. Yet it eventually "froze out" to form the atoms of today's world. Now, scientists are taking a closer look at this subatomic soup and the transition that took place by examining the nuclear phase diagram, a type of map that reveals different phases of the components of atomic nuclei--from free quarks and gluons to the clusters of protons and neutrons that make up the cores of atoms today.

In order to learn a bit more about these particles, the researchers turned to the Relativistic Heavy Ion Collider. Using this instrument, they smashed atomic nuclei together at close to the speed of light as sophisticated detectors and powerful supercomputers helped the researchers make sense of the data. By studying the collision debris and comparing experimental observations with predictions from complex calculations, the scientists were able to plot specific points on the nuclear phase diagram.

In order to plot the key points where the transition takes place, the researchers are hunting for large fluctuations in the excess of certain kinds of particles produced from collision to collision. By looking at millions of collision events over a wide range of energies, RHIC's detectors can pick up the fluctuations as likely signatures of the transition.

"At RHIC's top energy, where we know we've essentially 'melted' the protons and neutrons to produce a plasma of quarks and gluons--similar to what existed some 13.8 billion years ago--protons and antiprotons are produced in nearly equal amounts," said Frithjof Karsch, one of the researchers, in a news release. "But as you go to lower energies, where a denser quark soup is produced, we expect to see more protons than antiprotons, with the excess number of protons fluctuating from collision to collision."

The scientists didn't just use the RHIC, though. They also used supercomputers, which simulated the types of fluctuations you'd expect for the wide range of temperatures and densities at RHIC. More specifically, they mathematically modeled all the possible interactions of subatomic quarks and gluons as governed by the theory of Quantum Chromodynamics, or QCD. These supercomputers looked at interactions of quarks and gluons placed at discrete points on an imaginary four-dimensional "lattice" that accounts for three spatial dimensions plus time.

The scientists are repeating the process for many experimentally measured values of fluctuations over the wide range of beam energies available at RHIC. This helps the researchers to trace the line of the map that shows how the transition from quark soup to ordinary matters changes with temperature and density.

The findings could help physicists better understand the world we live in. In addition, by learning about the very beginnings of our universe, researchers can better understand particles today.