BUILDING
BLOCKS OF
MATTER
BBoM-halfttl.4/16/03 5/8/03 5:47 PM Page i
EDITORIAL BOARD
Editor in Chief
John S. Rigden
American Institute of Physics
Editors
Jonathan Bagger
Johns Hopkins University
Roger H. Stuewer
University of Minnesota
BUILDING
BLOCKS OF
MATTER
A Supplement to the
MACMILLAN
ENCYCLOPEDIA OF PHYSICS
John S. Rigden
Editor in Chief
BBoM-ttl pg.4/16/03 5/8/03 5:58 PM Page 1
Building Blocks of Matter: A Supplement to the Macmillan Encyclopedia of Physics
John S. Rigden, Editor in Chief
©2003 by Macmillan Reference USA.
Macmillan Reference USA is an imprint of
The Gale Group, Inc., a division of Thomson
Learning, Inc.
Macmillan Reference USA
TM

Fax: 248-699-8074 or 800-762-4058
While every effort has been made to ensure
the reliability of the information presented in
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lisher. Errors brought to the attention of the
publisher and verified to the satisfaction of
the publisher will be corrected in future edi-
tions.
Library of Congress Cataloging-in-Publication Data
Building blocks of matter : a supplement to the Macmillan encyclopedia
of physics / edited by John S. Rigden.
p. cm.
Includes bibliographical references and index.
ISBN 0-02-865703-9 (hardcover : alk. paper)
1. Particles (Nuclear physics) I. Rigden, John S. II. Macmillan
encyclopedia of physics.
QC793.2 .B85 2003
539.7’2—dc21
2002013396
Printed in the United States of America
10 9 8 7 6 5 4 3 2 1
CONTENTS
v
Preface vii

language of mathematics. However, the goal of ele-
mentary particle physics is very simple, and all the ef-
forts of elementary particle physicists are directed
toward that simple goal: to identify the basic build-
ing blocks of matter and to understand how they in-
teract to produce the material world we observe.
This encyclopedia contains articles intended for
a broad audience of general readers and is designed
to edify and give readers an appreciation for one of
the most active and productive areas of physics
throughout the twentieth century and to the present
time. On the one hand, most of the articles have
been written in ordinary language and provide a
solid base in particle physics concepts and history for
those who are new to the field. On the other hand,
some topics in particle physics are difficult to express
in everyday words, and in the articles on such topics,
symbols appear and even an occasional equation.
Even these articles, however, are written so that the
reader with little physics background can capture a
general sense of the topic covered.
Several features of the encyclopedia are de-
signed to help the general reader navigate the lan-
guage of physics and mathematics included in the
articles on the more complex topics. A glossary in
the back of the book provides definitions for terms
that may be unknown to the reader, both in the field
of physics and in related sciences. A list of common
abbreviations and acronyms at the beginning of the
book is included to aid readers unfamiliar with those

opment in what is now called particle physics extends
back almost three millennia. The time line demon-
strates the commanding grip that the desire to iden-
tify the basic building blocks of matter has had on
the minds of past and present scientists. Biographi-
cal articles of physicists who have made seminal con-
tributions to our understanding of the material world
complete the encyclopedia’s coverage of the history
of particle physics. The selection of physicists for the
biographies was based on the desire to provide a his-
torical background for the topics presented in this
encyclopedia, and so no living physicist was included.
Since experimentation is a vital part of particle
physics, detailed articles discuss the technologies
used to discover particles, including current accel-
erator types and subsystems. Articles also profile the
international laboratories that house these acceler-
ators, describing experiments, both historic and
current, conducted at these labs. Articles on case
studies are included to provide the reader with
more in-depth information as to how these tech-
nologies contribute to the past and continuing search
for particles.
Particle physics both affects and is affected by
other sciences as well as by the political and philo-
sophical environment. Articles discuss the interac-
tion of particle physics and cosmology, astrophysics,
philosophy, culture, and metaphysics. Also included
are articles describing the spin-off technologies cre-
ated in the search for particles as well as the fund-

INTRODUCTION
ix
Physicists distinguish between classical and modern
physics. The classical era began in the Scientific Rev-
olution of the seventeenth century and extended
throughout the eighteenth and most of the nine-
teenth centuries. By then there were rumblings
among some prominent physicists that their subject
was complete, that no more basic physics remained
to be discovered. Then, in 1895, Wilhelm Conrad
Röntgen discovered X rays, and abruptly, although
perhaps unknowingly, the modern era of physics be-
gan. During the following year Henri Becquerel dis-
covered radioactivity, and in 1897 the work of several
physicists culminated in the discovery of the electron,
which is generally credited to J. J. Thomson. With
the first subatomic particle, the electron, to account
for, physicists knew that a new era was under way.
The idea of basic building blocks of matter is at
least 2,600 years old. In the sixth century
B
.
C
.
E
.
Thales proposed that all things reduced to water,
and, coming out of the Greek-Roman eras and for
centuries to come, the four basic elements were
thought to be earth, water, fire, and air. The atomic

stituents. The electron is elementary. The proton,
long considered to be an elementary particle, does
have parts—three quarks. The proton is not ele-
mentary. There are currently twelve elementary par-
ticles that physicists believe make up the observable
matter throughout the universe: six quarks—up,
down, charm, strange, top, and bottom—and six
leptons—electron, electron neutrino, muon, muon
neutrino, tau, and tau neutrino—all of which fit
nicely into three groups, called generations, each
consisting of two quarks and two leptons. The first
generation consists of the four lightest particles—the
up and down quarks and the electron and the elec-
tron neutrino—which are the particles responsible
for ordinary matter as we currently know it. The com-
position of dark matter remains a mystery. The par-
ticles of the second and third generations are
successively more massive, and these heavier parti-
cles are believed to have played roles during the mo-
ments following the Big Bang. The twelve elementary
particles make up the Standard Model.
The electron and proton were discovered by ex-
perimental set-ups built on a small table. By contrast,
quarks were discovered by means of vast accelera-
tors with dimensions measured in miles and with
subsystems that dwarfed the physicists walking among
them. The century’s trend toward larger and larger
accelerators was necessitated by the need for higher
and higher energies. In turn, higher energies were
required to probe the innards of particles such as

ergy pushes it apart. What is dark energy? Will the ex-
pansive effect of dark energy override the contractive
effect of dark matter? Why do the elementary parti-
cles have their particular masses? Will the Higgs bo-
son bring understanding to this question? Gravitation
remains to be unified with the other basic interactions.
What will be required to accomplish this unification?
The answers to such questions may transform the con-
ceptual landscape of physics and, in the process, fun-
damentally alter the way humans view their world.
During the past two decades, nature’s extremes
have been linked. At one extreme are the elemen-
tary particles with their infinitesimal sizes and masses;
at the other extreme is the universe with its incom-
prehensibly immense size and mass. The detailed
knowledge of elementary particles accumulated over
the past century has illuminated events immediately
following the Big Bang and has provided a reason-
able explanation of how the universe evolved from
the zero-of-time to its current state fifteen billion
years later. The physics of elementary particles has
joined hands with cosmology, and together they have
brought knowledge and understanding to a level that
could not have been imagined when the electron was
first observed in 1897. Of course, many questions,
major questions, await answers; and many details, sig-
nificant details, await elaboration. Good science
begets good questions.
At a practical level, particle physics has dramat-
ically changed contemporary culture. Many of the

the explanatory line of logic back down to the par-
ticles? Only further scientific experimentation will
provide the answer.
John S. Rigden
BUILDING BLOCKS OF MATTER
xi
INTRODUCTION
READER’S GUIDE
xiii
Accelerator Laboratories
Beijing Accelerator Laboratory
Brookhaven National Laboratory
Budker Institute of Nuclear Physics
CERN (European Laboratory for Particle Physics)
Cornell Newman Laboratory for Elementary Parti-
cle Physics
DESY (Deutsches Elektronen-Synchrotron Labora-
tory)
Fermilab
Japanese High-Energy Accelerator Research Orga-
nization, KEK
SLAC (Stanford Linear Accelerator Center)
Thomas Jefferson National Accelerator Facility
Accelerator Subsystems and Technologies
Beam Transport
Cooling, Particle
Detectors
Extraction Systems
Injector System
Accelerator Types

Dirac, Paul
Einstein, Albert
Fermi, Enrico
Feynman, Richard
Kendall, Henry
Lawrence, Ernest Orlando
Noether, Emmy
Pauli, Wolfgang
Reines, Frederick
Rutherford, Ernest
Salam, Abdus
Schwinger, Julian
Thomson, Joseph John
Tomonaga, Sin-itiro
Wigner, Eugene
Wilson, Robert R.
Wu, Chien-Shiung
Yukawa, Hideki
Case Studies
Case Study: Gravitational Wave Detection, LIGO
Case Study: LHC Collider Detectors, ATLAS and
CMS
Case Study: Long Baseline Neutrino Detectors,
K2K, MINOS, and OPERA
Case Study: Super-Kamiokande and the Discovery
of Neutrino Oscillations
Detectors
Detectors and Subsystems
Detectors, Astrophysical
Detectors, Collider

Metaphysics
Philosophy and Particle Physics
Particles
Atom
Axion
Boson, Gauge
Boson, Higgs
Charmonium
Hadron, Heavy
J/
␺
Lepton
Neutrino
Quarks
Resonances
Physical Concepts
Antimatter
Broken Symmetry
Conservation Laws
Energy
Energy, Center-of-Mass
Energy, Rest
BUILDING BLOCKS OF MATTER
xiv
READER’S GUIDE
Feynman Diagrams
Higgs Phenomenon
Momentum
Particle
Quantum Statistics

CP Symmetry Violation
Electroweak Symmetry Breaking
Family
Flavor Symmetry
SU(3)
Supersymmetry
Symmetry Principles
BUILDING BLOCKS OF MATTER
xv
READER’S GUIDE
LIST OF ARTICLES
xvii
A
Accelerator
Gerald F. Dugan
Accelerators, Colliding Beams:
Electron-Positron
Raphael Littauer
David Rice
Accelerators, Colliding Beams:
Electron-Proton
David H. Saxon
Accelerators, Colliding Beams: Hadron
Gordon Fraser
Accelerators, Early
Robert W. Seidel
Accelerators, Fixed-target: Electron
William K. Brooks Jr.
Accelerators, Fixed-target: Proton
John Marriner

Big Bang Nucleosynthesis
Roger K. Ulrich
Boson, Gauge
Sally Dawson
Boson, Higgs
Howard E. Haber
Broken Symmetry
John F. Donoghue
Brookhaven National Laboratory
Robert P. Crease
Budker Institute of Nuclear Physics
Alexander N. Skrinsky
C
Case Study: Gravitational Wave Detection,
LIGO
Neil Ashby
Case Study: LHC Collider Detectors, ATLAS
and CMS
Howard A. Gordon
Case Study: Long Baseline Neutrino Detectors,
K2K, MINOS, and OPERA
Stanley G. Wojcicki
Case Study: Super-Kamiokande and the
Discovery of Neutrino Oscillations
Henry W. Sobel
CERN (European Laboratory for Particle
Physics)
Maurice Jacob
Chadwick, James
Roger H. Stuewer

Dark Matter
Keith Olive
DESY (Deutsches Elektronen-Synchrotron
Laboratory)
Paul Söding
Detectors
Stephen Pordes
Detectors and Subsystems
Paul Grannis
Detectors, Astrophysical
Steven Ritz
BUILDING BLOCKS OF MATTER
xviii
LIST OF ARTICLES
Detectors, Collider
David Hitlin
Detectors, Fixed-target
Kevin McFarland
Detectors, Particle
L. Donald Isenhower
Devices, Accelerating
William A. Barletta
Dirac, Paul
Helge Kragh
E
Eightfold Way
Jonathan L. Rosner
Einstein, Albert
Michel Janssen
Electron, Discovery of

Albert Wattenberg
Fermilab
Adrienne W. Kolb
Feynman Diagrams
Lewis Ryder
Feynman, Richard
Silvan S. Schweber
Flavor Symmetry
Benjamin Grinstein
Funding of Particle Physics
Wolfgang K. H. Panofsky
G
Gauge Theory
Vernon Barger
Charles Goebel
Grand Unification
Vernon Barger
Graham Kribs
H
Hadron, Heavy
Adam F. Falk
Higgs Phenomenon
Christopher T. Hill
BUILDING BLOCKS OF MATTER
xix
LIST OF ARTICLES
Hubble Constant
Wendy L. Freedman
I
Inflation

Lawrence A. Coleman
Muon, Discovery of
Robert H. March
N
Neutrino
Chung W. Kim
Neutrino Oscillations
Francis Halzen
M.C. Gonzalez-Garcia
Neutrino, Discovery of
Laurie M. Brown
Neutrino, Solar
Wick C. Haxton
Neutron, Discovery of
Roger H. Stuewer
Noether, Emmy
Nina Byers
O
Outlook
Bruce Winstein
BUILDING BLOCKS OF MATTER
xx
LIST OF ARTICLES
P
Parity, Nonconservation of
Lewis Ryder
Particle
Michael Dine
Particle Identification
David H. Saxon

Harry J. Lipkin
R
Radiation, Cherenkov
Blair N. Ratcliff
Radiation, Synchrotron
Katharina Baur
Radioactivity
Benjamin Bayman
Radioactivity, Discovery of
Lawrence Badash
Reines, Frederick
Robert G. Arns
Relativity
Richard H. Price
Renormalization
John F. Donoghue
Resonances
Gabor Domokos
Rutherford, Ernest
Lawrence Badash
S
Salam, Abdus
T. W. B. Kibble
Scattering
JoAnne Hewett
Schwinger, Julian
Silvan S. Schweber
SLAC (Stanford Linear Accelerator Center)
Helen Quinn
SSC

Terry P. Walker
V
Virtual Processes
Robert Garisto
Rashmi Ray
W, X
Wigner, Eugene
Erich Vogt
Wilson, Robert R.
Albert Silverman
Boyce D. McDaniel
Wu, Chien-Shiung
Noemie Benczer Koller
Y
Yukawa, Hideki
Laurie M. Brown
Z
Z Factory
Nan Phinney
BUILDING BLOCKS OF MATTER
xxii
LIST OF ARTICLES
LIST OF CONTRIBUTORS
xxiii
Kazuo Abe
Japanese High-Energy Accelerator Research
Organization
Japanese High-Energy Accelerator
Research Organization, KEK
Peter Arnold

University of Minnesota, Minneapolis
Cyclotron
Radioactivity
Karl Berkelman
Cornell University
Cornell Laboratory for Elementary Particle
Physics
William K. Brooks Jr.
Thomas Jefferson National Accelerator Facility
Accelerators, Fixed-Target: Electron
Laurie M. Brown
Northwestern University
Neutrino, Discovery of
Pauli, Wolfgang
Tomonaga, Sin-itiro
Yukawa, Hideki
Nina Byers
University of California, Los Angeles
Noether, Emmy
Lawrence S. Cardman
Thomas Jefferson National Accelerator Facility and
University of Virginia
Thomas Jefferson National Accelerator
Facility
R. Sekhar Chivukula
Boston University
Electroweak Symmetry Breaking
Lawrence A. Coleman
University of Arkansas at Little Rock
Momentum

Energy
Energy, Center-of-Mass
Energy, Rest
Isobel Falconer
Open University, UK
Electron, Discovery of
Thomson, Joseph John
Adam F. Falk
Johns Hopkins University
Hadron, Heavy
Jonathan L. Feng
University of California, Irvine
Supersymmetry
Kenneth W. Ford
American Institute of Physics (retired)
Conservation Laws
Gordon Fraser
Accelerators, Colliding Beams: Hadron
Wendy L. Freedman
Carnegie Observatories, Pasadena, CA
Hubble Constant
Robert Garisto
Physical Review Letters
Virtual Processes
Marcelo Gleiser
Dartmouth College
Phase Transitions
Charles Goebel
University of Wisconsin, Madison
Gauge Theory

Beijing Accelerator Laboratory
Donald Hartill
Cornell University
Injector System
Wick C. Haxton
University of Washington, Seattle
Neutrino, Solar
Kenneth J. Heller
University of Minnesota, Minneapolis
Particle Physics, Elementary
JoAnne Hewett
Stanford Linear Accelerator Center
CKM Matrix
Scattering
Christopher T. Hill
Fermi National Accelerator Laboratory
Higgs Phenomenon
David Hitlin
California Institute of Technology
Detectors, Collider
L. Donald Isenhower
Abilene Christian University
Detectors, Particle
Maurice Jacob
European Laboratory for Particle Physics (CERN)
CERN (European Laboratory for Particle
Physics)
International Nature of Particle Physics
Michel Janssen
University of Minnesota, Minneapolis

Grand Unification
G. Peter Lepage
Cornell University
Lattice Gauge Theory
Harry J. Lipkin
Weismann Institute of Science, Rehovot, Israel
Quarks, Discovery of
BUILDING BLOCKS OF MATTER
xxv
LIST OF CONTRIBUTORS
Raphael Littauer
Cornell University
Accelerators, Colliding Beams: Electron-
Positron
Byron G. Lundberg
Fermi National Accelerator Laboratory
Experiment: Discovery of the Tau
Neutrino
Robert H. March
University of Wisconsin, Madison
Muon, Discovery of
William J. Marciano
Brookhaven National Laboratory
Quantum Electrodynamics
John Marriner
Fermi National Accelerator Laboratory
Accelerators, Fixed-Target: Proton
Cooling, Particle
Extraction Systems
Boyce D. McDaniel

Stanford Linear Accelerator Center
Z Factory
William H. Pickering
California Institute of Technology (emeritus)
Anderson, Carl D.
Joseph Polchinski
University of California, Santa Barbara
String Theory
John Polkinghorne
Queens College, Cambridge, UK
Culture and Particle Physics
Metaphysics
Stephen Pordes
Fermi National Accelerator Laboratory
Detectors
Richard H. Price
University of Utah, Salt Lake City
Relativity
Helen Quinn
Stanford Linear Accelerator Center
J/
␺
SLAC (Stanford Linear Accelerator
Center)
David Rainwater
Fermi National Accelerator Laboratory
Experiment: Search for the Higgs Boson
Krishna Rajagopal
Massachusetts Institute of Technology
Quark-Gluon Plasma