- Dramatic progress has been made in particle physics during the past two decades. A series of important experimental discoveries has firmly established the existence of a subnuclear world of quarks and leptons. The protons and neutrons (“nucleons”), which form nuclei, are no longer regarded as elementary particles but are found to be made of quarks. That is. in the sequence molecules → atoms → nuclei → nucleons, there is now known to be another “layer in the structure of matter.” However, the present euphoria in particle physics transcends this re-markable discovery. The excitement is due to the realization that the dynamics of quarks and leptons can be described by an extension of the sort of quantum field theory' that proved successful in describing the electromagnetic interactions of charged particles. To be more precise, the fundamental interactions are widely believed to be described by quantum field theories possessing local gauge symmetry. One of the aims of this book is to transmit a glimpse of the amazing beauty and power of these gauge theories. We discuss quarks and leptons, and explain how they interact through the exchange of gauge field quanta (photons, gluons, and weak bosons).
- We are very- conscious that this book has been written at a crucial time when pertinent questions regarding the existence of the weak bosons and the stability of the proton may soon be decided experimentally. Some sections of the book should therefore be approached with a degree of caution, bearing in mind that the promising theory of today may only be the effective phenomenology of the theory of tomorrow'. But no further apology will be made for our enthusiasm for gauge theories.
- We have endeavored to provide the reader with sufficient background to understand the relevance of the present experimental assault upon the nature of matter and to appreciate contemporary theoretical speculations. The required magnetic and weak interactions of leptons and quarks; and quantum chromo-dynamics (QCD), which describes the strong interactions of quarks and gluons. The primary purpose of this book is to introduce these ideas in the simplest possible way. We assume only a basic knowledge of nonrelativistic quantum mechanics1 and the theory of special relativity. We spend considerable time introducing quantum electrodynamics (QED) and try to establish a working familiarity with the Feynman rules. These techniques are subsequently generalized and applied to quantum chromodynamics and to the theory' of weak interactions.
- The emphasis of the book is pedagogical. This has several implications. No attempt is made to cover each subject completely. Examples are chosen solely on pedagogical merit and not because of their historic importance. The book does not contain the references to the original scientific papers. However, we do refer to books and appropriate review articles whenever possible, and of course no credit for original discovery' is implied by our choice. A supplementary' reading list can be found at the end of the book, and we also encourage the students to read the original papers mentioned in these articles. A deliberate effort is made to present material which will be of immediate interest to the student, irrespective of his experimental or theoretical bias. It is possible that aspiring theorists may feel that an injustice has been done to the subtle beauty of the formalism, while experimentalists may justifiably argue that the role of experimental discoveries is insufficiently emphasized. Fortunately, the field is rich in excellent books and review articles covering such material, and we hope that our guidance toward alternative presentations will remedy these defects.
- Although the book is primarily written as an introductory course in particle physics, we list several other teaching options. The accompanying flow diagram gives some idea of the material covered in the various chapters.
- One teaching option is based on the belief that because of its repeated phenomenological successes, modern particle physics, or at least some aspects of it, is suitable material for an advanced quantum mechanics2 course alongside the more traditional subjects such as atomic physics. For this purpose, we suggest Chapters 3 through 6, with further examples from Chapter 12. together perhaps with parts of Chapter 14.
- An undergraduate course on the introduction of the Feynman rules for QED could be based on Chapters 3 through 6.
- The sequence of Chapters 3 through 11 could serve as an introduction to quantum chromodynamics.
- A course on weak and electromagnetic interactions could cover Chapters 3 through 6 and 12 and 13, perhaps supplemented with parts of Chapters 14 and 15.
- For a standard introductory particle physics course, it may not be possible to cover the full text in depth, and Chapters 7. 10, 11, 14. and 15 can be partially or completely omitted.
- Exercises are provided throughout the text, and several of the problems are an integral part of the discussion. Outline solutions to selected problems are given at the end of the book, particularly when the exercise provides a crucial link in the text.
- This book was developed and written with the encouragement of students and friends at the Universities of Durham and Wisconsin. [snip … ]
Text Colour Conventions (see disclaimer)
- Blue: Text by me; © Theo Todman, 2020
- Mauve: Text by correspondent(s) or other author(s); © the author(s)