The first seconds of the universe were filled with a boiling, chaotic inferno. It was packed with a dense plasma: a soup-like fire, made up of some of the tiniest particles in the universe. Unbelievably, physicists have recreated a substance that they think is very similar to this early universe plasma. Albeit, just the tiniest drop.
The drop of plasma was created in the Large Hadron Collider (LHC). It is made up of two types of subatomic particles: quarks and gluons. Quarks are the building blocks of particles like protons and neutrons, while gluons are in charge of the strong interaction force between quarks. The new quark-gluon plasma is the hottest liquid that has ever been created in a laboratory at 4 trillionoC (7 trillionoF). Fitting for a plasma like the one at the birth of the universe.
The plasma was created after a collision between a proton and a lead nucleus. The physicists had always thought that this collision wouldn't produce enough particles (around 1,000) to create a plasma. A collision between two lead nuclei, for comparison, is known to produce plasma but creates twenty times more particles (around 25,000) following collision. However, the results defied their expectations.
“Before the CMS experimental results, it had been thought the medium created in a proton on lead collisions would be too small to create a quark-gluon plasma,” said Quan Wang, a physicist from Kansas University (KU), in a statement. "The analysis presented in this paper indicates, contrary to expectations, a quark-gluon plasma can be created in very asymmetric proton on lead collisions."
“This is the first paper that clearly shows multiple particles are correlated to each other in proton-lead collisions, similar to what is observed in lead-lead collisions where quark-gluon plasma is produced,” added Yen-Jie Lee, from the Michigan Institute of Technology (MIT). “This is probably the first evidence that the smallest droplet of quark-gluon plasma is produced in proton-lead collisions.”
This new research looks at particle physics with a fresh perspective. Instead of counting individual numbers of particles, the plasma forces physicists to look at the behavior of a volume of particles.
There is also speculation that this plasma replicates the conditions of the early universe. “It’s believed to correspond to the state of the universe shortly after the Big Bang,” Wang continued. This plasma is different to other quark-gluon plasma that have been made before now. The interactions in this plasma are extremely strong, which distinguishes it from other plasmas which interact infrequently (like gas particles). This is what makes the researchers think it might be similar to an early universe plasma.
“While we believe the state of the universe about a microsecond after the Big Bang consisted of a quark-gluon plasma, there is still much that we don't fully understand about the properties of quark-gluon plasma.”