Supersymmetry in Particle Physics: An Elementary Introduction ,

Ian
Aitchison
,
Cambridge U. Press
,
New York
, 2007. $65.00 (222 pp.). ISBN 978-0-521-88023-7

Supersymmetry extends the Poincaré symmetry group to include transformations that pair fermions with bosons. First discovered in the 1970s in the context of string theory, supersymmetry was later found to have many theoretical advantages when applied to the standard model of particle physics. In the minimal supersymmetric standard model (MSSM), every particle has a superpartner whose spin differs by one half; the superpartners are expected to have masses around the TeV scale. In recent decades, TeV-scale super-symmetry has emerged as the leading candidate for new physics that will be tested thoroughly at CERN’s Large Hadron Collider.

Given its appeal, it is not surprising that there have been a number of excellent modern pedagogical texts on the subject, of which Ian Aitchison’s Super-symmetry in Particle Physics: An Elementary Introduction is a welcome addition. The book aims to provide a practical introduction to the basics of supersymmetry and the MSSM, and it succeeds admirably at that task. The book is a worthy companion to such texts as Weak Scale Supersymmetry: From Superfields to Scattering Events (Cambridge University Press, 2006) and Theory and Phenomenology of Sparticles: An Account of Four-Dimensional N = 1 Supersymmetry in High Energy Physics (World Scientific, 2005), both of which were reviewed in PHYSICS TODAY in December 2006. Aitchison’s text is a slim volume consisting essentially of two parts: an introduction to global super–symmetry and an overview of the MSSM. The primary strength of the text is its accessible treatment of supersymmetry theory; Aitchison bases his presentation on a “do-it-yourself” approach that emphasizes intuition and physical understanding rather than on the more formal deductive approach of most texts. One highlight is the presentation of the 4D spinor manipulations needed for discussing the MSSM—the reader will not be required to master any additional formalism beyond that of basic quantum field theory. Starting from the Dirac equation, Aitchison guides the reader through a detailed treatment, including the notational complexities, of spinors associated with Hermann Weyl and Ettore Majorana. Although the notation and conventions in Supersymmetry in Particle Physics occasionally differ from many of the standard references, for newcomers to TeV-scale supersymmetry, the clear presentation of the spinor formalism may alone be worth the price of the book.

Aitchison’s intuitive approach carries through the rest of the text. Super-symmetry is introduced through the explicit construction of a toy theory involving one complex scalar field and one Weyl fermion—familiar to some as the Wess-Zumino model, but without interactions or auxiliary fields. The supersymmetry algebra and the full Wess–Zumino model are then developed through familiar analogies with ordinary quantum field theories. Though not much discussion is devoted to the technically more challenging ideas of superspace and superfields, a sufficient amount of material is included for the reader to be able to understand the basic concepts that are relevant for the MSSM. Aitchison includes in the first half of the text many worked-out examples and problems for further study, and he occasionally pauses to preview the MSSM so that the reader doesn’t get lost in formalism. In the second half, the MSSM is introduced, and with it, a discussion of the Higgs sector and many useful results from MSSM phenomenology, including several cross-section formulas for superpartner production and decay at colliders. Here the approach is more standard, but the inclusion of those phenomenological topics makes the text a largely self-contained reference.

Although Supersymmetry in Particle Physics is a succinct introduction to TeV-scale supersymmetry, it is not nearly as comprehensive as other texts, including Weak Scale Supersymmetry and Theory and Phenomenology of Sparticles. This is not the text to learn about the history of supersymmetry or to obtain an encyclopedic guide to the literature. A number of important theoretical issues are referred to only briefly; they are often relegated to parenthetical statements or footnotes. Aitchison’s approach also may not be ideal for most theorists, who are likely to prefer the more formal and deductive approach of other texts. However, those drawbacks are pointed out by Aitchison himself in the preface, which, along with the introductory chapter, should not be skipped.

Any student or practicing physicist who wants to learn about the phenomenological implications of TeV-scale supersymmetry without spending the time to master the more mathematical approaches to the subject would do well to acquire a copy of Supersymmetry in Particle Physics. It is a unique text that has value both on its own accord and as a supplement to larger and more comprehensive texts. This is indeed entry-level supersymmetry in its best and most practical sense.