Color confinement

As confinement (English for, captivity ' ) is called in particle physics, the phenomenon that particles with color charge do not occur in isolation. Quarks and gluons occur only in bound states and can not be measured as free particles in principle. A complete theoretical description of the experimental findings is pending.

Experimental findings

In nature and in experiments so far only colorless objects, ie mesons ( quark-antiquark pairs) or baryons ( three-quark states) are observed. Quarks and gluons are therefore still only " locked " ( engl. confined ) in these states and not free. Attempts with high energies the quarks to " disconnect", led to a spontaneous pairing of quarks and antiquarks. One assumes that gluons can come together to glueballs, which are measurable binding states with no valence quarks.

In the framework of quantum chromodynamics ( quantum field theory of strong interactions ), the confinement is related to the color charge of quarks and gluons: color charges come in three types, and each color charge, there is an opposite anti-color charge. If a particle contains a total of one unit of a color charge and a unit of the corresponding anti-color charge, it is color- charge neutral. Likewise, a particle, in which each of the three color charges ( or each of the three anti-color charges ) occurs in the same thickness, color charge neutral. More generally, it means confinement: " In nature, only colorless objects come before. " Non - existence of ( inevitably color- charged) free individual quarks, the so-called current quarks is thus a special case of this general formulation. She also has the consequence that the strong interaction has only a very short range, since no color charge is outwardly visible.

Using computer simulations, one can show that between two static quarks (pair creation is suppressed ) forms a potential which increases linearly with the distance. This leads to a linear potential with increasing distance remains constant force, as opposed to, for example, gravitation and electromagnetism, where the force decreases rapidly with distance from. This linear potential is explained that bind due to the color charge, the gluons into a strand whose energy increases with the length. A color to separate charged particles from the rest, would therefore require extremely high energy. A separation of the quarks from gluons is therefore only possible under certain conditions and for a very short time. In reality, the energy does not grow to infinity. Above a certain energy (or a certain distance between the quarks ) couples can arise that bind with the previous new colorless states new quark-antiquark. This effect is referred to as a " string -breaking ".

The exact mechanisms of how this strand is formed, is related to the interactions of gluons with each other or the interaction of gluons with vacuum fluctuations together and is the subject of current research. There are several scenarios, like this strand can form a unified picture has not yet been enforced.

A full understanding of the confinement requires the development of appropriate methods to solve within the quantum many-body problems.

A potential well is commonly referred to as quantum mechanical confinement (localization).