Fifty years of particle physics research has produced an elegant and concise theory of particle interactions at the subnuclear level. This book presents the experimental foundations of that theory. A collection of reprints alone would, perhaps, have been adequate were the audience simply practicing particle physicists, but we wished to make this material accessible to advanced undergraduates, graduate students, and physicists with other fields of specialization. The text that accompanies each selection of reprints is designed to introduce the fundamental concepts pertinent to the articles and to provide the necessary background information. A good undergraduate training in physics is adequate for understanding the material, except perhaps some of the more theoretical material presented in smaller print and some portions of Chapters 6, 7, 8, and 12, which can be skipped by the less advanced reader.

Each of the chapters treats a particular aspect of particle physics, with the topics given basically in historical order. The first chapter summarizes the development of atomic and nuclear physics during the first third of the twentieth century and concludes with the discoveries of the neutron and the positron. The two succeeding chapters present weakly decaying non-strange and strange particles, and the next two the antibaryons and the resonances. Chapters 6 and 7 deal with weak interactions, parity and CP violation.