Heavy ion collisions are high-energy experiments where nuclei of heavy atoms—such as gold or lead—are accelerated to near light speed and smashed together. These collisions, conducted in particle accelerators like the Large Hadron Collider (LHC) and RHIC (Relativistic Heavy Ion Collider), aim to recreate conditions similar to those of the early universe, just microseconds after the Big Bang.
Key features of heavy ion collisions:
- The extreme energy density and temperature (over a trillion kelvin) melt protons and neutrons, liberating quarks and gluons from their confinement and forming a quark–gluon plasma (QGP).
- This plasma is believed to resemble the primordial soup that existed in the early universe before matter formed.
- The QGP behaves like an almost perfect fluid with very low viscosity, flowing smoothly without resistance—surprising many physicists who expected it to behave more like a gas.
These collisions help scientists:
- Study the strong nuclear force under extreme conditions.
- Investigate the transition between confined hadronic matter and deconfined quark-gluon plasma.
- Understand how matter formed and evolved in the early universe.
Heavy ion collision experiments offer a rare window into the fundamental behavior of matter at the highest energies and densities achievable in the laboratory, pushing the frontiers of quantum chromodynamics and cosmology.