Paul Langacker is senior scientist at Princeton University, visitor at the Institute for Advanced Study in Princeton, and professor emeritus of physics at the University of Pennsylvania. He is the author of The Standard Model and Beyond.

"This book is a very worthwhile, balanced, and useful summary of our current understanding of the fundamental laws of physics. Langacker covers a large amount of material in a very digestible way."—Savdeep Sethi, University of Chicago

• Preface vii 1. The Epic Quest 1 2 The Three Eras 7 2.1 The Ingredients 7 2.2 Prehistory 9 2.3 The Era of Exploration 12 2.4 The Standard Model Era 22 2.5 Beyond the Standard Model 26 3 Particles, Interactions, and Cosmology 29 3.1 The Fundamental Particles 29 3.2 The Interactions 35 3.3 Cosmology 41 4 The Standard Model 51 4.1 Gauge Invariance and QED 51 4.2 Internal Symmetries 65 4.3 Yang-Mills Theories 70 4.4 Quantum Chromodynamics 73 4.5 The SU(2) x U(1) Model 83 4.6 The Higgs Mechanism 86 4.7 The Electroweak Theory 91 5 What Don't We Know? 137 5.1 Arbitrariness and Tuning 138 5.2 Terra Incognita: Unanswered Questions 151 5.3 Are the Paradigms Correct? 163 6 How Will We Find Out? 175 6.1 The Ideas 175 6.2 The Tests 211 7. Epilogue: The Dream 223 Postscript: Run 2 226 Glossary 229 Bibliography 251 Index 259

Paul Langacker is senior scientist at Princeton University, visitor at the Institute for Advanced Study in Princeton, and professor emeritus of physics at the University of Pennsylvania. He is the author of The Standard Model and Beyond.

"This book is a very worthwhile, balanced, and useful summary of our current understanding of the fundamental laws of physics. Langacker covers a large amount of material in a very digestible way."—Savdeep Sethi, University of Chicago

• Preface vii 1. The Epic Quest 1 2 The Three Eras 7 2.1 The Ingredients 7 2.2 Prehistory 9 2.3 The Era of Exploration 12 2.4 The Standard Model Era 22 2.5 Beyond the Standard Model 26 3 Particles, Interactions, and Cosmology 29 3.1 The Fundamental Particles 29 3.2 The Interactions 35 3.3 Cosmology 41 4 The Standard Model 51 4.1 Gauge Invariance and QED 51 4.2 Internal Symmetries 65 4.3 Yang-Mills Theories 70 4.4 Quantum Chromodynamics 73 4.5 The SU(2) x U(1) Model 83 4.6 The Higgs Mechanism 86 4.7 The Electroweak Theory 91 5 What Don't We Know? 137 5.1 Arbitrariness and Tuning 138 5.2 Terra Incognita: Unanswered Questions 151 5.3 Are the Paradigms Correct? 163 6 How Will We Find Out? 175 6.1 The Ideas 175 6.2 The Tests 211 7. Epilogue: The Dream 223 Postscript: Run 2 226 Glossary 229 Bibliography 251 Index 259