Quantum Chromodynamics and Related Topics
- Pp. 72-85 (14)Takehisa Fujita and Naohiro Kanda
Quantum chromodynamics is the theoretical frame work in which one can treat the physics of the strong interactions. This is the non-abelian gauge field theory, and it cannot be solved in the perturbation theory since the free Lagrangian densities of quarks and gluons are not gauge invariant. In the perturbation theory, we describe all the physical observables in terms of the properties of quarks and gluons, and if they are not related to physical observables, then there is no point of employing the perturbation theory. Here, we also discuss the nucleon-nucleon interactions based on the meson exchange processes and present the calculation of the two pion exchange potential. Further, we discuss some physical observables in connection with quarks, that is, the magnetic moments of nucleons in terms of quark model and the total cross section ratio between &#963;e+e-&#8594; hadrons and &#963;e+e-&#8594;&#956;+&#956;-. These physical quantities are related to the quark degrees of freedom.