Valence quark

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Under valence (or constituent quark ) refers to the curd that the most important properties of a hadron as mass , momentum , electric charge and spin determined. In the case of the proton , these are one down and two up quarks. The naming is based on the valence electrons of atomic physics , which are essentially responsible for the chemical properties of atoms .

However, this is only a simplified approximation, since according to the theory of strong interaction ( quantum chromodynamics , QCD), the quarks in the hadron also interact with virtual quark-antiquark pairs ( sea ​​quarks ) and virtual gluons , which are constantly emerging from each other in the QCD. In addition to the valence quarks, these components from the “quark-gluon lake” contribute to the mass, momentum and spin of the hadrons.

This leads u. a. to a constituent quark mass that is significantly higher than the mass of the current quarks , which behave like free particles in the limit case of high energies : z. B. in the case of the light up and down quarks to values ​​of around 300  MeV / c² instead of less MeV / c². The valence quarks contribute to the total spin z. For example, the proton is only about 50 percent, while the beam energy is 30 to 50 percent (values ​​still unsecured). This leads to high center of gravity energies .