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 .