Partonquark

Partonquark is a theoretical concept in particle physics that describes the internal structure of hadrons, such as protons and neutrons. It was introduced by Richard Feynman in the late 1960s to explain the results of high-energy scattering experiments. At the time, it was observed that when electrons were scattered off protons at high energies, the protons behaved as if they were composed of point-like, non-interacting constituents. Feynman termed these constituents "partons."

Later, with the development of quantum chromodynamics (QCD), the theory of the strong nuclear force, these partons were identified with quarks and gluons. Quarks are the fundamental fermions that make up hadrons, while gluons are the force carriers of the strong interaction. Therefore, the term "parton" is often used interchangeably with "quark or gluon" in the context of a hadron's internal structure.

The parton model suggests that at high energies, the quarks and gluons within a hadron act almost independently. This is due to a phenomenon called asymptotic freedom, where the strong force between quarks becomes weaker as they get closer together. However, at lower energies, the quarks are confined within the hadron by the strong force, which becomes stronger as they are pulled apart.

The distribution of partons within a hadron is not uniform and depends on the momentum fraction they carry. This distribution is described by parton distribution functions (PDFs), which are determined experimentally and play a crucial role in calculations for high-energy particle collisions. The parton model has been incredibly successful in explaining a wide range of experimental results in particle physics.