J. J. Sakurai's treatment of various elementary particle phenomena, is written for those not completely familiar with field theory who wish to gain insight into theoretical problems. Since the manuscript for his book was completed, a very important development has taken place in particle physics-the discovery of the p, w, and n mesons: in view of this development, the author has added a new section devoted exclusively to these new mesons and resonances. Originally published in 1964. The Princeton Legacy Library uses the latest print-on-demand technology to again make available previously out-of-print books from the distinguished backlist of Princeton University Press. These editions preserve the original texts of these important books while presenting them in durable paperback and hardcover editions. The goal of the Princeton Legacy Library is to vastly increase access to the rich scholarly heritage found in the thousands of books published by Princeton University Press since its founding in 1905.