Robert Purdy - Particle Physics: An Introduction

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Original title and copyright: The Fundamentals of Particle Physics by Robert Purdy. Copyright 2017 Pantaneto Press. All rights reserved.

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R. Purdy. Particle Physics: An Introduction.

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To my parents, who have always listened to my ramblings

Particle physics remains one of the most popular aspects of the study of modern physics. Not only is the subject popular among physics students, it also captures the imagination of the general public. Admittedly, a part of the reason for this may be that the machines constructed for the fields continued development are easily some of the most awe-inspiring engineering feats in human history. However, I do not think that this is the full story. Rather, I believe that the appeal of particle physics is that it addresses some of the key questions that lead people to an interest in physics in the first place. First, particle physics, arguably more than any other discipline, aims to answer the question of what the universe is ultimately made of. In my opinion, the only other discipline to address such weighty problems is cosmology, and the two could not be more different in their approach. While cosmology studies the overall structure and history of the universe on the grandest scaleswhat we might call the holistic approachparticle physics is concerned with building a universe from its simplest constituents. We can think of this as a constructionist or bottom up approach to understanding the world. This said, the aim of the two disciplines is ultimately the same, and so despite the many orders of magnitude between the scales of their realms of study, there is a surprising amount of overlap between the two. This is a point that we will explore a little in the final chapter of this book.

The second reason I believe particle physics appeals to many is that it is built upon a few guiding principles. Chief among these is the role that symmetry plays in our universe. As we will see throughout this text, symmetry and its implications play a pivotal role in the field of particle physics. As such, there is an elegance and beauty underlying much of modern particle physics. Indeed, it is the desire to produce a more symmetrical theory that has led to many of the developments in the history of particle physics, including as-yet purely hypothetical developments such as supersymmetry and grand unification. The drive to develop theories of the world that are elegant, simple, and symmetrical is not unique to particle physics of course: it is a principle adhered to by all areas of physics, dating back at least as far as William of Ockham and his famous razor in the fourteenth century. However, since particle physics develops this idea to its full potential, this is just another reason that students of physics are commonly drawn to this field.

This book has three main aims. First, I wish to introduce the reader to the concepts of particle physics. As a theorist, my approach to this is mainly to come at things from a theoretical point of view. As such, the emphasis is on developing the ideas of particle physics that are mathematically consistent and then showing that they apply to the real world. This is as opposed to the (arguably more historically accurate) approach of finding and refining theories that fit the experimental observations. In this way, the reader will hopefully develop an appreciation for the elegance of the subject and its reliance on symmetry and simplicity as guiding principles. This said, even as a theorist, I must acknowledge that occasionally it is necessary to observe the real world to ensure that our theories are on the right track. As such, an introduction is given in to some aspects of experimental physics and of how we may compare theory with experiment.