Preface

Elementary Particle Physics, HINUS, Zagreb, 1997

The contemporary particle physics has reached the level of a standard theory. This means that the fundamental constituents of matter, its species and interactions have been embedded into a self-consistent framework, submitted to experimental verification. These features include "particle physics" into an undergraduate level curriculum, and call for an adequate textbook. Previously, the author found that the most adequate textbook for such a level was the one by Griffiths [Gr87], a younger brother of Halzen-Martin's book [HaM 84]. However, during the decade following the appearance of Griffiths' book, new chapters have been written by a living field of science. Embedding them into lectures of a two-semester course at the University of Zagreb has resulted in the appearance of this textbook.

The text has been arranged in three layers, representing self-containing units, which (depending on the number of hours at disposal) can be presented separately: the first two chapters, the following four, and the final seventh chapter. Following the main aim to bring a student to the frontline of current research as soon as possible, the historical exposition is reduced merely to an introduction to the basic principles: the quantum principle and the relativistic principle in chapter 2 followed by an introduction to the guauge principle in chapter 3.

The application of the gauge principle to separate fundamental interactions represents the central part of this book. The presentation of electrodynamics is far from being complete - its presentation is merely to facilitate the understanding of other fundamental interactions. Thereby, it seems to be unavoidable that a student accepts certain rules (e.g. Feynman rules) as a tool enabling him to perform a calculation of real physical processes. Postponing the study of the foundations of these rules resembles the use of computers without further knowledge on digital electronics and Turing's machines.

Accordingly, the role of quantum electrodynamics (QED) for us is to master to a certain extent over the dynamics of the strong force, quantum chromodynamics (QCD), in Chapter 4. In a similar way, we make an approach to the exciting dynamics of particle species transmutation, quantum flavourdynamics (QFD) in Chapter 5.

The heart of the book is represented by a selection of a few representative processes, having a lot of common for all these kinds of dynamics: mastering the calculation of $e^- \mu^-$ scattering and $e^+ e^-$ annihilation in Sec. 3.3.3 opens the entrance to a study of QCD in Sec.4.1.1 and 4.2.1 , and calculations of weak decays in Sec. 5.2.1. Sec. 5.3 leads us to the electroweak unification, which, upon introducing the concepts of spontaneous symmetry breaking and the Higgs mechanism in Ch.6, encircles the standard model of electroweak-strong interactions. The sections marked the asterisk (*) are attached to Ch.7, giving an indication of the main directions beyond the standard model.