In the first fractions of a second after the Big Bang lingers a question at the heart of our very existence: why does the universe contain matter but almost no antimatter? The laws of physics tell us that equal amounts of matter and antimatter were produced in the early universe but then, something odd happened. Matter won out over antimatter; had it not, the universe today would be dark and barren.

But how and when did this occur? Helen Quinn and Yossi Nir guide readers into the very heart of this mystery-and along the way offer an exhilarating grand tour of cutting-edge physics. They explain both the history of antimatter and recent advances in particle physics and cosmology. And they discuss the enormous, high-precision experiments that particle physicists are undertaking to test the laws of physics at their most fundamental levels, and how their results reveal tantalizing new possibilities for solving this puzzle at the heart of the cosmos.

The Mystery of the Missing Antimatter is at once a history of ideas and an exploration of modern science and the frontiers of human knowledge. This exciting, accessible book reveals how the interplay of theory and experimentation advances our understanding and redefines the questions we ask about our universe.

The aim of this book is to use one of the most fundamental questions facing physicists today--why the observable universe contains a quantifiable asymmetry between the amount of matter and antimatter--to take readers on a tour of a host of important concepts in modern particle physics and cosmology. Helen Quinn and Yossi Nir have impeccable particle-physics credentials, and their book is a timely and informative contribution.

This book deals with one of the most fundamental mysteries of nature. Perhaps it is fitting that the authors have taken a very ambitious approach to writing about it: they cover just about every aspect of modern particle physics. This book will appeal to a serious reader whose curiosity will be rewarded by a wealth of ideas and history related to the subject of matter-antimatter asymmetry.

With the theme of a murder mystery installed in the reader by a silhouette on the cover, this book takes the reader on a tour de force of the case at hand. This book takes the reader on breathtaking foray into the depths of the particle that make-up our body and our worlds. And like an affable Dr. Watson, the reader can journey with [Helen Quinn and Yossi Nir] as they explore this still unsolved case.

"Their profile of the possible culprit will challenge yet reward readers with an understanding of a fascinating subject." Gilbert Taylor, Booklist

[A] remarkable book which provides one of the most satisfying tours of particle physics I have ever read.

In this page-turner, true science is written in the thrilling tone of science fiction. Quinn and Nir present the history of the antimatter problem and discuss its impact on our understanding of the cosmos--all without introducing a single equation or even a Greek letter. They reveal tantalizing possibilities for solving this puzzle, made possible by high-precision experiments that particle physicists like Quinn and Nir themselves undertake. For anyone wanting to know how physics works and physicists think, the writers make one of the greatest unsolved problems in physics both comprehensive and compelling.

I just had the great pleasure of reading Quinn and Nir's new book, . The book reads like an exciting real-life mystery--and even the appendix offers a fascinating bit of scientific history. It tells a very compelling story in a very accessible manner, and I predict it will get the large and thoughtful readership it deserves.

The standard model of particle physics is Quinn and Nir's arena for discussing one of its inadequacies: it has yet to answer why in the trillionths of a second after the big bang, there was a tiny numerical superiority of matter over antimatter; if there was not, atoms would not have formed. Addressing nonscientists, the authors describe the nature of this intriguing problem...[This book] will challenge yet reward readers with understanding of a fascinating subject at the frontier of science.

[For] anyone wanting to know how physics works and physicists think, the writers have made a difficult topic comprehensible as well as compelling.

This is a most remarkable book from many points of view. Using the matter-antimatter asymmetry in the universe as a central theme, it tracks the reasoning behind the essential ideas comprising the standard model of particle physics, its shortcomings, and its impact on our knowledge of the cosmos. And it does all this without a single equation, not even a Greek letter. This asymmetry accounts for our very existence, and Quinn and Nir have been in the thick of the theoretical developments. This is indeed heady stuff.

Two distinguished physicists, Quinn and Nir trace in some detail both the history of modern particle physics and its relation to cosmology. Even though the text is free from equations, the authors clearly explain the details of the theories presented and their development. The logic and the meaning of the connections among the ideas make it interesting and challenging.This is a fine book that belongs in college libraries.

Helen R. Quinn is professor of physics at the Stanford Linear Accelerator Center at Stanford University. A member of the National Academy of Sciences, she is the coauthor of "The Charm of Strange Quarks: Mysteries and Revolutions of Particle Physics". Yossi Nir is professor of physics at the Weizmann Institute of Science in Israel.

Acknowledgments xi

Chapter 1: Prelude: The Mystery of the Missing Antimatter 1

Chapter 2: Constant Physics in an Evolving Universe 7

Universal Laws 7

Hubble and the Expanding Universe 8

Red-shifts: Evidence for an Expanding Universe 12

Numbers Large and Small 17

What Do We Mean by "Universe"? 19

Chapter 3: As the Universe Expands 21

Running the Clock Forward: Radiation 21

Running the Clock Forward: Dark Matter 26

Running the Clock Forward: Light Nuclei 29

Running the Clock Forward: Matter and Antimatter 32

Chapter 4: What Is Antimatter? 36

What Is Matter? 36

Dirac Introduces Antimatter 42

Experiments Confirm That Antimatter Exists 45

Radioactive Decays of Nuclei 48

Chapter 5: Enter Neutrinos 51

Pauli: The Beta Decay Puzzle 51

Fermi: The Theory of Neutrinos Develops 53

Cowan and Reines: Neutrinos Detected 55

Chapter 6: Mesons 57

Yukawa and the Pi-Meson 57

Strange Mesons, Strange Quantum Concepts 61

Chapter 7: Through the Looking Glass 63

What Physicists Mean by the Term Symmetry 63

A Gedanken Experiment 64

The Actual Experiment 67

Chapter 8: Through the Looking Antiglass 73

Another Gedanken Experiment 73

Cronin and Fitch: Matter and Antimatter Do Not Follow the Same Laws 75

Chapter 9: The Survival of Matter 80

Pauli's Other Letter: Initial Conditions on the Universe 80

Sakharov: The Conditions Needed to Develop an Imbalance 84

Cosmology with Sakharov's Conditions Met: Baryogenesis 88

Chapter 10: Enter Quarks 91

Quarks 91

Why Don't We See the Quarks? 96

What about Dark Matter? 100

The Missing Charm, the Surprising Tau 101

The Standard Model: Particles and Interactions 107

Chapter 11: Energy Rules 111

Stored Energy, Forces, and Energy Conservation 111

Force Fields Permeating Space 114

Field Theory and the Energy Function 116

Chapter 12: Symmetry Rules 121

Symmetries as Answers to the Question "Why?" 121

Symmetries and Conservation Laws 123

Space-Time Symmetries 124

Gauge Symmetries 126

Discrete Symmetries 128

Baryon and Lepton Number Conservation? 130

Chapter 13: Standard Model Gauge Symmetries 132

The Symmetry behind the Electromagnetic Interaction 132

The Symmetry behind the Strong Interaction 134

The Symmetry behind the Weak Interaction 137

Chapter 14: A Missing Piece 140

The Puzzle of Particle Masses 140

How Do We Describe Nothing? 146

At Last, CP Violated in the Standard Model 153

Chapter 15: It Still Doesn't Work! 159

Running the Clock Forward: The Standard Model 159

Now What? 163

Chapter 16: Tools of the Trade 168

Accelerators 168

Detectors 172

Data Handling and Analysis 177

How Projects Develop 178

Chapter 17: Searching for Clues 180

Where Are We Now? 180

Testing the Standard Model in B-Meson Decays 182

Oddone: How to Build B Factories? 184

Running the B Factories: The First Test 190

Chapter 18: Speculations 194

Why Are We Never Satisfied? 194

Grand Unified Theories 195

Supersymmetry 201

Way beyond the Standard Model 204

Chapter 19: Neutrino Surprises 206

Davis, Bahcall, Koshiba: Solar Neutrinos 206

Quantum Neutrino Properties 214

Chapter 20: Following the New Clues 222

Some Things We Know 222

Some Things We Speculate About 225

Fitting It All Together 227

Chapter 21: Finale 231

Appendix: A Timeline of Particle Physics and Cosmology 233

Perspective 233

Relevant Nineteenth-Century Developments 234

1900-1930: Development of Quantum Ideas, Beginnings of

Scientific Cosmology 238

1930-1950: New Particles, New Ideas 245

1930-1960s: The Advent of Accelerator Experiments--The Particle Explosion; Implications of Expanding Universe Explored 249

1964-1973: Formulation of the Modern View of Particles and the

Universe 256

Two Standard Models Emerge--Particles and Cosmology 263

Index 273