Quark Size < 10.19 m 0.000511 -1 0.006 -1/3 V muon <0.0002 0 charm 1.3 2/3 ..... P. neutrino e- 0.106 -1 strange 0.1 -1/3 <0.02 0 top 175 2/3 Atom Size - 10.10 m Flavor Quarks. Le w+ w- -1 0.938 0.8 o 0.940 o 1.116 z A neutron deuys 10 a proton. on elearon. and an antineutrino via a V1rtual (mediating) W bown. This 1$ neutron Pd euy. Model of ES AND INTERACTIONS 'at mdudes the theory 01 strong mteraClions (quantum chromodynamlcl or 0(0) and the un,f,ed :ause it IS one 01 the fundamental mteraClions even lhough not part 01 the "Standard Model" force carriers BOSONS spin = 0, 1, 2, Unified EI,ectroweak spin = 1 Stron'g (CO~(),r) Spil}'=:.l • Mass EleÜric ,'Ma}s __ -~ _E h!ctric _ Nilme Name GeV/c2 charge 'GiN/cZ 'chä'rge o 0 80,4 -1 80.4 +1 Electric Charge Quarks. Gluons Gluons Mesons SÜ ltaon -1 0.494 0 25 Not applicable to quarks rho ud ..1 o.no db B·zero 0 5.279 0 The Charm of Strange Quarks R. Michael Barnett Henry Mühry Helen R. Quinn The Charm of Strange Quarks Mysteries and Revolutions of Particle Physics With Contributions by Gordon J. Aubrecht Robert N. Cahn Jonathan Dorfan Max Dresden Gerson Goldhaber John David Jackson Keith Olive With 95 Illustrations, 5 in Full Color AlP , Springer PRESS R. Michael Bamett Henry Mühry Physics Division Department of Physics Lawrence Berkeley National Laboratory University of Basel MS 50A-5101 Basel Berkeley, CA 94720 Switzerland USA Helen R. Quinn Stanford Linear Acce1erator Center Stanford University Stanford, CA USA Library of Congress Cataloging-in-Publication Data Bamett, R. Michael. The charm of strange quarks / mysteries and revolutions of particle physics / R. Michael Bamett, Henry Mühry, Helen R. Quinn. p. cm. Includes bibliographical references and index. ISBN 978-1-4684-9510-2 ISBN 978-0-387-21534-1 (eBook) DOI 10.1007/978-0-387-21534-1 I. Particles (Nuclear physics) l. Mühry, Henry. II. Quinn, Helen. III. Title. QC776.B28 2000 539.7'2-dc21 99-36215 Printed on acid-free paper. © 2000 Springer-Verlag New York, Inc. Softcover reprint of the hardcover 1s t edition 2000 AlP Press is an imprint of Springer-Verlag New Y ork, Inc. All rights reserved. This work may not be translated or copied in whole or in part without the written permission ofthe publisher (Springer-Verlag New York, Inc., 175 Fifth Avenue, New York, NY 10010, USA), except for brief excerpts in connection with reviews or scholarly analysis. Use in connection with any form of information storage and retrieval, electronic adaptation, computer software, or by simiIar or dissimilar methodology now known or hereafter developed is forbidden. The use of general descriptive names, trade names, trademarks, etc., in this publication, even if the former are not especially identified, is not to be taken as a sign that such names, as understood by the Trade Marks and Merchandise Marks Act, may accordingly be used free1y by anyone. Production managed by Timothy Taylor; manufacturing supervised by Erica Bresler. Photocomposed copy prepared from the authors' TEX files. 9 8 7 6 5 4 3 2 I ISBN 978-1-4684-9510-2 Preface A force so weak that humans cannot experience it, yet responsible for our very existence ... A particle (the quark) not visible directly in any experiment, yet known to be the prime constituent of the atomic nucleus ... A particle (the neutrino) so ephemeral it can traverse the diameter of Earth without interacting, yet physicists can make beams of them and cause collisions ... Matter dark and unlike anything we experience on Earth, yet a major constituent of the universe ... These and similar mysteries are part of the revolution that has made particle physics a forefront science. Too often, however, the excitement of these ideas seems hidden behind complex presentations. The intent of the authors of this book is to bring the excitement and a basic understanding of this fundamental topic to the public and especially to students. This book also includes very recent developments in particle physics and cosmology. For example, some of the great mysteries of physics may be re solved if we postulate that there are extra dimensions of space, unseen by hu mans (this may involve string theory and black holes). Recent astrophysical experiments suggest that the expansion of the uni verse may be accelerating. Both of these topics are discussed here. Science is as much about the process of discovery as it is about the ideas that that process generates. Our aim is to give the reader an inside view to the vi Preface process, exploring the tools and experiments by which the evidence that led to these ideas was uncovered. One remarkable aspect of modem physics is that the smallest objects in the world and the largest (the universe) are intimately tied together. This book shows how our knowledge of cosmology and astrophysics teIls us about funda mental particles and forces, and vice versa. A very lively chronology of the events of modem partic1e physics shows not only the leaming process but also the missteps that occur in real research, and how even correct new ideas move only gradually from the status of fringe specu lation to accepted view. The book begins with the exciting drama of the discovery of the charm quark. It goes on to introduce quarks and the other fundamental partic1es. The four fundamental forces and their consequences are described. We next turn our at tention to the enormous detectors that are used to observe the universe's smallest partic1es. We show what happens when, deep inside these detectors, very ener getic partic1e collisions occur. Then comes the discussion of cosmology and the chronology of partic1e physics. The book conc1udes with some appendices that will make our book more readily useful in a c1assroom setting and will interest teachers and other readers too. The authors have worked with a group of physicists and high school and college teachers in the Contemporary Physics Education Project (CPEP) for the past 12 years. CPEP is the non-profit group that created the very popular chart of the fundamental particles and forces (shown in the color pages). All the content of that chart (and much more) is explained here. Through our work with teachers and educators in CPEP, we honed our skills of explaining partic1e phys ics to students and the public; many CPEP members and their students have proofread our manuscript, and their questions and suggestions helped refine it. Further information and materials about the topics of this book can be ob tained at the websites below. These inc1ude the award-winning website The Partic1e Adventure http://particleAdventure.org and the well-known wall chart on Fundamental Particles and Interactions http://pdg.lbl.gov/cpep.html R. Michael Barnett Lawrence Berkeley National Laboratory Acknow ledgments The authors thank members of the Contemporary Physics Education Project and the Particle Data Group for their assistance, advice, and proofreading. We especially acknowledge the efforts of Chris Fanjul, Charles Groom, Donald Groom, Charley Harper, Frederick Priebe, Robert Reiland, and Thad Zaleskie wicz. Heroic efforts by Betty Armstrong and Andria Erzberger were vital in bringing this book to fruition. Major contributions to Chapter 1 were made by Michael Riordan of the Stanford Linear Accelerator Center. The text in Chapter 8 on the accelerating uni verse and in Chapter 9 on extra dimensions were origi nally writtin by Robert Knop and Chris Kolda, respectively, both of Lawrence Berkeley National Laboratory. The surviving authors of this book recall with fondness the memory of our colleague Max Dresden, teacher, physicist, historian of physics and friend, who delighted many with his inimitable lecture style and his personal anecdotes of the great scientists of the early days of quantum physics. Contents Preface ........................................................................................................... v Acknowledgments ................................ ......................................................... vii Contributors ......................................................... .............................. ............ xi Prologue ............................................................ ....................... ...................... xiii 1. The November Revolution .................................................................. . 2. The Elusive Trail to the Standard Model............................................ 11 3. The Mystery of Flavors ....................................................................... 45 4. Carriers of Force .......................................................... .............. .......... 71 5. Anything that Can Happen Will Happen ............................................ 85 6. Precision Detectors Lead to Great Discoveries .............................. ..... 95 7. Creating Extremely High-Energy Collisions ....................................... 121 8. Astrophysics Meets Particle Physics .... .......................... ............ ......... 143 9. The Status of the Standard Model ....................................................... 169 10. A Historical Perspective on Particle Physics ...................................... 189 A. Appendix: The Greek Alphabet ........................................................... 209 x Contents B. Appendix: Glossary .............................................................................. 211 C. Appendix: How Detectors Work ......................................................... 223 D. Appendix: Basic Physics Concepts Applied to Particles .................... 235 E. Appendix: Suggested Reading ................ ... ........ ....... ... ... .............. ....... 285 People Index .. ... .......... ... .... .... ....... ........ ..... .................................................... 293 General Index ........................ ....... ........ ..... ............ ......... ........ ... ....... ..... ... ..... 295