In the preceding chapter we discussed the electromagnetic interaction, which was responsible for the energy loss and small angle scattering of charged particles, and for the production and interactions of photons. However, there are other types of processes where the nuclear interaction may represent the dominant mechanism. These include particle creation reactions, interactions at high energies or large momentum transfers, and interactions of neutral particles other than the photon. In this chapter we will examine some of the basic properties of nuclear interactions. We will not be directly concerned with the physics underlying subnuclear phenomena. Instead, our main concern will be to survey its overall features, principally total cross sections, particle production multiplicities, and angular distributions.

We will first discuss the strong interaction. The group of particles known as hadrons is influenced by this interaction. Next we will briefly discuss the weak interaction, which is responsible for the interactions of neutrinos in matter and for the decay of most quasistable particles.

Strong interactions

The group of particles known as hadrons are subject to the strong interaction in matter. The neutron is an ideal probe of this interaction since it has no appreciable electromagnetic interactions. We have seen that the cross sections for most electromagnetic interactions are strongly peaked in the forward direction and fall off with increasing energy. Thus, away from the forward direction, the high energy behavior of all hadrons is determined by the strong interaction.