REVOLUTIONARY progress in particle physics over the past two decades has
given birth to a radically new and simple view of the fundamental
constituents of matter and the interactions among them. Quarks and
leptons, at least 1,000 times smaller than the nucleus, if not truly
structure less and indivisible, have been identified as the elementary
particles for this generation of scientists, and perhaps beyond. The four
fundamental interactions — strong, weak, electromagnetic and
gravitational — owe their form to symmetries, expressed in the mathematical language of gauge theories. A common language holds out the
prospect of unification of the forces of Nature, extending the achievement
of Maxwell and, in the popular mind, surpassing the dream of Einstein. The
resulting paradigm embraces a staggering richness of phenomena. It is
conceptually simple, but entails a daunting sophistication of theoretical
tools, and a remoteness from common experience.
This dramatic progress raises challenges that are shared by other
rapidly developing disciplines: how to communicate the essence of the
field to nonspecialists, how to propagate a teacher's wisdom to
beginning students without forcing them to penetrate a thicket of detail.
The solution proposed to us in these volumes by two gifted teachers lies
in the telling of tales, in inferences by analogy, in intuitive modes of
thought communicated by word of mouth from scientific parent to child.
Aiming for a wider dissemination of the oral tradition of physics by means
of the written word, Gottfried and Weisskopf have set down the substance
of lectures given over a period of several years to summer students at
CERN, the European laboratory for particle physics.
The result is not a traditional textbook: there are no exercises, not many
detailed calculations and very few references from which the reader might
learn more. Forgoing a comprehensive bibliography may preserve some of
the immediacy of the lectures from which the book developed. but it is
very frustrating in a work of this length.
In contrast to the absence of detailed references or suggested readings,
there are footnotes on nearly every page containing qualifications and
elaborations of the textual material. I found these
distracting; in many cases they contain remarks too detailed to interest
the reader for whom the book is apparently intended. Some footnotes are
uninformative: the remark that time reversal is an exception to the rule
that symmetry operations are represented by unitary operators would be far
more useful if it contained the information that time reversal is
represented by an antiunitary operator, and a definition. Elsewhere, the
text would have benefited from rewriting to eliminate ambiguity or to
incorporate the subtle thoughts now consigned to footnotes.
The first volume is devoted to a 170-page introduction to the basic
concepts and phenomena of particle physics. Brief treatments of
prehistory, nonrelativistic quantum mechanics and atomic physics,
relativistic quantum mechanics and nuclear phenomena precede the main
agenda. All the principal topics are touched upon: the spectroscopy of the
strongly interacting particles, their quantum numbers and the related
global symmetries; quarks and leptons; and the phenomenology of the
strong, weak and electromagnetic interactions. While the selection of
topics is apt, much of this presentation is imprecise or muddled, and some
of it is simply wrong. It is not correct, as Fig. 12 would have it, that
the φ-meson is an SU(3) flavour singlet; it is a bound state of strange
quark and antiquark, which is as nonsinglet as can be. There are many
similar slips of the pen, as well as examples of faulty logic. Although
this volume does give an engaging overview of the subject and a hint of
current thinking and current issues, it is disappointing that it is not
more consistently reliable. I can imagine giving it to a student who has
already assimilated Perkins's Introduction to Particle Physics for a rainy
day read, but not for close study.
The second volume revisits the subjects treated in the first in more
detail and at a deeper level. It is generally more successful, but
presumably is intended as counterpoint to a standard treatment, rather
than as a plausible replacement. An introductory chapter on quantum
electrodynamics introduces the authors' notations and summarizes a number
of experimental tests of QED, but gives less emphasis to the decisive role
of gauge invariance than it merits in the modern view. A descriptive
chapter on the static properties of hadrons might well have been
incorporated into Vol 1. Quantum chromodynamics, the theory of the strong
interactions of quarks and gluons, is developed from the point of view of
colour-electric and colour-magnetic field strengths. The treatment of
antiscreening by an electromagnetic analogy is not standard textbook fare,
so it is pleasing to see it worked out here. The impact is
weakened by relegating part of the punch line to an appendix, however. A
discussion of the bag model is murky and out of date,
and raises, but does not settle, the question of the η and η’
masses. The
chapter on deeply inelastic lepton-hadron scattering, the source of much
of our experimental information on the structure of the proton, suffers
from inconsistent, nonstandard notation and ancient data. The essential
ideas are here, but in a rather graceless form. Notational to and fro that
might seem spontaneous on a blackboard appears simply indecisive in
print.
The treatment of electroweak interactions analyses the phenomenology of
neutral current interactions and properties of gauge bosons before
coming to terms with the spontaneous breaking of the electroweak gauge
symmetry. Notwithstanding an insightful discussion of the recognition of
the gauge symmetry, this chapter does not entirely succeed. When
intuitive arguments and elementary techniques lead without noticeable
effort to insights about profound and challenging problems, it is
wondrous to behold. But when the approach comes up short, it simply calls
attention to the self-imposed handicaps and interferes with the subject
itself. Again there is all too frequently an annoying imprecision: a
charge
asymmetry in the reaction e+e– →
μ+ μ– is not a parity-violating effect,
but only evidence for some mechanism besides single-photon exchange.
The oral tradition must stand for impeccable standards of scholarship,
as well as insight. When at last it appears, the treatment of hidden symmetries contains some instructive remarks on the analogy with
superconductivity and ferromagnetism, and is worth reading.
Overall, there is a disappointing inattention to detail in the production
of the book. Assiduous copyediting should have removed awkward turns of
phrase, disagreements between subject and verb, and artefacts from the
original manuscript. Typographical errors are common enough to be
intrusive.
Despite the authors' contagious love of the subject and their desire to
communicate the excitement and progress of recent years to a broad
audience, Concepts of Particle Physics is no royal road to wisdom.
Viewed not as a textbook to be studied, but as an anthology of lectures to
be browsed, it has a place in departmental libraries.
Chris Quigg is Deputy Director for Operations of the Superconducting Super Collider
Central Design Group, Lawrence Berkeley Laboratory, Berkeley, California 94720,
USA, and Visiting Professor in the Department of Physics, University of
California, Berkeley.