Oral tradition
Chris Quigg

Concepts of Particle Physics, Vols 1 and 2. By Kurt Gottfried and Victor F. Weisskopf. Oxford University Press: 1984 and 1987. Vol. 1 pp. 204; pbk $13.95, £9.95; Vol. 2 pp. 432; hbk $45, £40.

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.

Published in Nature 330, 31 (1987).