This final chapter has three goals. First, we want to show how experimentalists have measured properties of subatomic particles. This section takes the form of a survey of some of the applicable techniques. Second, we want to discuss some of the considerations involved in measurements of particle interactions, such as total cross sections, elastic differential cross sections, polarization experiments, and new particle searches. Finally, we want to illustrate these measurements with examples of actual particle physics experiments.

Particle properties

In this section we will describe some of the methods used to measure the basic properties of the elementary particles. As mentioned in Chapter 1, these properties include charge, mass, spin, magnetic moment, lifetime, and branching ratios. Many specialized techniques have been developed for measuring some of these properties, particularly for the electron and nucleons. We will not attempt to survey all the applicable procedures for each particle, since many of the methods use techniques from atomic and molecular physics that fall outside the scope of this book. Instead we will follow the philosophy of the preceding chapters and discuss selected examples in more detail.

Charge

The sign of a particle's charge may be inferred from the direction of its deflection (if any) in a magnetic field of known orientation. The magnitude of the charge can be determined if the momentum of the particle and the strength of the magnetic field are known.