The aim of the book is to introduce the electroweak theory and the methods that have been developed for calculating physical processes. To this end it was decided to divide the book into three major parts.

The road to unification

This part gives a general view of early developments when the theory was based on numerous empirical rules. These topics are extensively discussed in older books on weak interactions, and I selected a few topics among them, such as form factors, CVC, and PCAC, in order to give a general impression of how the field developed. It should serve as an introduction to a few topics from the early period of weak interactions and as a guide to articles and texts. Appreciation of the first part requires familiarity with the methods developed at that time. The readers who find this part too brief or difficult may proceed to the second part, where gauge theories are introduced.

Field theories with global or local symmetries

This part presents field theories based on continuous symmetries and guides the student to the electroweak theory based on the group SU(2) X U(1). Special effort has been made to present it in a simple and pedagogical way. For this reason the chapters are short and accompanied by references that the reader or lecturer can consult.

Experimental consequences and comparisons

The third part of the book covers some of the exciting discoveries that took place in the process of verifying the electroweak theory.