ANTIMATTER, THE ULTIMATE MIRROR
G. Fraser, Cambridge University Press, 2000, pp: 207, ISBN 0-521-65252-9 (hc); Price: $24.95.

Antimatter - the Ultimate Mirror by Gordon Fraser is his attempt to make particle physics, and specifically antimatter, more accessible to those with little or no background in physics.

Antimatter has been a feature of elementary particle physics since its accidental prediction by Paul Dirac in the late 1920s and the discovery of the positron by Carl Anderson in 1932. It is now widely accepted that for every type of particle there exists an antiparticle with opposite quantum numbers (such as charge, strangeness, baryon number) although some neutral particles are their own antiparticle (e.g. the neutral pion). However, this basic symmetry of Nature is not obvious in our universe. Somehow, early in the history of the universe, a slight asymmetry between matter and anti-matter developed, with the result that after all the opposites annihilated, we were left with a universe containing only matter. All evidence suggests that antiparticles (such as positrons and anti-protons) can only be found in particle physics labs and high energy astrophysical processes. There is no naturally occurring low energy antimatter left in the universe.

These are intriguing concepts and it seems a shame that so many people are unaware of them. For a large fraction of the population, antimatter is the stuff of science fiction. Gordon Fraser has written a book to rectify this situation. Fraser is the editor of the CERN Courier and the author of several other works that also strive to bring particle physics to the general population. This book, his latest, is a good effort. Its appeal is mainly to those without much of a background in physics. This is because Fraser, probably having sensed early on that it may be difficult to fill an entire book with an entry-level account of antimatter, has expanded his task to include a history of particle physics from antiquity to present day. An interesting read for someone with little knowledge of the field, it offers up the usual lore of the field, including stories about Michael Faraday's humble origins and Richard Feynman's teenage experiences repairing radios. For people already acquainted with these anecdotes, along with the general progress of 20th century physics, the book is not worth reading. A more worthwhile book, although difficult to get, is "The Particle Explosion", by Close, Marten and Sutton (Oxford University Press).

Fraser's book has several factual errors as well as an irritating Europe vs. the US undercurrent which seems to have been carried over from his earlier book, The Quark Machines - How Europe fought the particle physics war. For example, he states that American scientists watched enviously as the muon was discovered in Europe. The muon was, in fact, discovered by Carl Anderson and Seth Neddermeyer in the US in 1936. When describing early results from the CERN p- experiments, Fraser states that quark jets had never been seen so clearly. Perhaps this is true of hadron collisions, but jet structure in electron-positron collisions at the PETRA collider in Hamburg was obvious years earlier, even at the level of the online event display. This is even stated in a later chapter, indicating a lack of integrity in the editing of the book.

The book also suffers from a poor choice of figures. Most are simply photographs of key players in the history of the field, and so are of dubious pedagogical value. Even this is not well done - a photograph of members of the team that discovered the anti-proton at Berkeley does not include the leaders, Segre and Chamberlain! It would have been better to include more line drawings that explain physics concepts as well as photographs of the equipment used to make some of the discoveries. A book on symmetry, which includes concepts such as parity violation and intrinsic spin, should include the classic diagram of a spinning top and its image in a mirror. Use of bubble chamber pictures or computer event displays would show the "reality" of some of the processes such as quark fragmentation into jets. A serious book about science has no room for a picture of Margaret Thatcher being shown around CERN, even if it is in the company of Alan Astbury. Incredibly, this is followed by a full-page reproduction of her letter congratulating the UA1 team on its detection of the W particle.

Even the layperson is not really well served by this book. Fraser, in an effort to explain complicated ideas to a wide audience, relies heavily on analogies but some of these are really not appropriate. For example, he compares the oscillating electric fields that accelerate particles in a cyclotron to the artificial hare that is chased by greyhounds at a racetrack. The analogy is not strained; it is simply wrong.

In summary, the idea behind this book is a good one and with a bit of care it could be made into a valuable addition to the popular science literature. In its present form it is a bit of a disappointment.

David Hanna
McGill University