ABSTRACT
Atomic nuclei are very complex systems including large numbers of strongly interacting protons and neutrons. It is now recognized that these nucleons are not fundamental building blocks with some meson clouds around them. Nucleons are composite particles, each including three valence quarks. Quantum chromodynamics (QCD) of quarks and gluons is accepted as the fundamental theory describing, among other phenomena, the structure and interactions of nucleons. Unfortunately, there are great difficulties in obtaining a reasonable solution of QCD to low energy phenomena like the structure of the nucleon. The interaction between two nucleons is even more complicated. In high energy experiments, the composite nature of nucleons is clearly manifest. For low energy phenomena, it is usually assumed that it is possible to ignore the internal structure of nucleons. Nucleons may then be considered as basic constituents of nuclei and their complicated interactions may be replaced by some interaction which is a function of their coordinates, momenta and spins. The latter may be determined by scattering of nucleons by nucleons and by properties of the deuteron.
