Frank Close

The quark parton model

The evidence that high-energy collisions of subatomic particles reveal the presence of quarks inside the proton and neutron is reviewed. Low-energy electron scattering from nuclei is described with reference to the manner in which it reveals the presence of protons in the nucleus; high-energy electron-proton interactions are then discussed and the presence of partons in the proton revealed by analogy. Then the basic ideas of the parton model are described and the evidence that partons are, in fact, quarks and electrically neutral gluons is discussed. The model is then applied to a variety of processes and is shown to correlate an enormous amount of data. Recent clues that the quark parton model is an approximation to a more fundamental theory are described, with particular reference to the possibility that quarks and gluons are the quanta of a field theory of strong interactions (quantum chromodynamics) analogous to the role that electrons and photons play in QED.

e + e − Annihilation

In recent years the development of electron-positron colliding beam facilities with high energies and intensities has opened a fascinating new window on particle structure. To date most attention has focused on electron-positron annihilation through the one-photon process, and it is with this aspect of e + e − collisions that we shall be primarily concerned.