Copenhagen University scientists studied the properties of a quark-gluon plasma, which existed in the first microsecond of the Big Bang. An unusual form of matter from which hadrons arose (particles consisting of quarks and antiquarks) was reproduced on a large hadron collider (tank), which allowed physicists to make more detail for the evolution of the universe at the very beginning of its existence. The results of the experiment are published in the magazine Physics Letters b.
Quark-gluon plasma (or quark soup) consists of quarks and gluons (carriers of strong interaction between quarks), which are in a state similar to the state of electrons and ions in a conventional plasma. The expansion of the universe led to the decay of the quark-gluon plasma on the hadron – particles to which include, for example, protons and neutrons. Gluons “glued” quarks with strong nuclear interaction, and quarks cannot exist in a free state (this phenomenon is called confinement). In a quark-gluon plasma, the confinement is missing.
In the course of the experiment, quantum soup received in collisions of lead cores, which were registered using the Alice detector to the tank. Important information about the properties of a quark-gluon plasma can be obtained by measuring the characteristics of anisotropic (differing depending on the direction) of the flows of particles formed after the collision. With the help of an algorithm analyzing the particle distribution, the researchers, in particular, confirmed that the kilk-gluon plasma can be considered as a liquid, and not gas, as physicists did before.
As scientists write, their results provide additional information about the initial conditions that exist at the time of the Birth of the Universe, and impose stronger limitations on the model of the evolution of a quark-gluon plasma created when a collision of heavy nuclei in the tank.