A state of matter where quarks and gluons are deconfined, created in high-energy particle collisions.Quark-gluon plasma (QGP) is a state of matter in which quarks and gluons, normally confined inside protons and neutrons, are freed to move over macroscopic distances. This state is believed to have existed microseconds after the Big Bang, filling the universe before particles condensed into hadrons. In laboratories, QGP is created by colliding heavy ions at relativistic speeds, such as at the Large Hadron Collider, producing temperatures over a trillion kelvin—hotter than the core of the Sun.
The concept was proposed in the 1970s, and the first experimental evidence emerged in 2000 at CERN's SPS, followed by conclusive results at RHIC in 2005. The LHC has since studied it in greater detail.
Under extreme energy density, the strong force that binds quarks into hadrons weakens due to asymptotic freedom: at short distances, quarks interact weakly. In a collision, the energy deposited melts the hadrons, creating a hot, dense soup of quarks and gluons. This plasma behaves like a nearly perfect fluid with very low viscosity, and it expands and cools, eventually hadronizing into particles detected by experiments. Jets of particles passing through the plasma lose energy, revealing its properties.
Research on quark-gluon plasma helps understand the strong force and the early universe, with applications in nuclear physics and astrophysics, though it has no direct technological use yet.
The quark-gluon plasma is so hot that it cannot be described by temperature alone; it also exhibits collective flow like a liquid, leading physicists to call it the 'perfect liquid'.




