Physicists at the Brookhaven National Laboratory (New York, USA) first obtained drops of quark-gluon plasma at the Relativistic Heavy Ion Collider (RHIC). A substance in a similar state, characterized by almost zero viscosity, existed in the first moments of the Big Bang. This is reported in an article published in the journal Nature Physics.
Quark-gluon plasma is an aggregate state of matter, in which hadrons - a class of elementary particles that include protons and neutrons - are divided into asymptotically free quarks and gluons. This state is similar to plasma, when atoms are ionized, charges are separated, and nuclei and electrons can move freely. However, the plasma remains quasi-neutral, that is, the total charge inside any part of it is zero. Inside hadrons, quarks are held together by confinement, while the colors (a special quantum characteristic) of each quark must compensate each other, as a result of which hadronic matter remains colorless. Quark-gluon plasma is quasi-colorless.
Quark-gluon plasma, which is formed at high temperatures, is an almost ideal liquid, in which there is no viscosity. It is believed that it existed in the first moments of the Big Bang and quickly cooled, which led to hadronization - the formation of colorless hadrons from colored quarks, antiquarks and gluons, which at low temperatures cannot exist in a free state.
Scientists conducted collisions at RHIC between gold atoms and accelerated ions: protons, deuterons and helium-3 nuclei - at an energy in the center of mass system (a system in which particles have equal and oppositely directed momenta) equal to 200 gigaelectronvolts. According to the theoretical model, if a quark-gluon plasma with an extremely low viscosity is formed during a collision, then the collider detectors should record clouds of particles that retain the "shape" of the accelerated ions. Protons leave a circular trail, deuterons an elliptical, and helium-3 triangular.
The results of the experiment showed that the observed patterns of particles released during the collision of gold atoms and ions coincide with those that should arise during the formation of droplets of quark-gluon plasma.