Hadronization is the process by which quarks and gluons—originally free in a high-energy state such as a quark-gluon plasma—combine to form composite particles called hadrons, such as protons, neutrons, and mesons.
This process occurs because quarks cannot exist freely in isolation due to the phenomenon of color confinement in quantum chromodynamics (QCD). As the system cools and energy decreases (such as after a high-energy collision or in the early universe), quarks and gluons bind together in color-neutral combinations:
- Three quarks form baryons (e.g., protons and neutrons),
- Quark–antiquark pairs form mesons (e.g., pions and kaons).
Hadronization happens extremely rapidly—within about 10⁻²³ seconds after a high-energy event. It plays a crucial role in:
- High-energy particle collisions in experiments like those at the LHC,
- The early universe, when matter first condensed after the Big Bang,
- Understanding how visible matter forms from fundamental constituents.
Since it involves strong-force dynamics at low energies, hadronization is difficult to calculate precisely and is often modeled using complex simulations and phenomenological models in particle physics.