Constructing Quarks: A Sociological History of Particle Physics
The title is a challenge. This is an account of the development of the standard model of particle physics, written not by a physicist but by a historian. This is certainly a suitable topic for a historian to analyse, and one might anticipate a refreshingly different account from an outsider sitting above the fray. This is indeed what is provided, though `refreshing' is not the right word; the viewpoint is so different that the scientific reader will find it at best thought-provoking, and at worst unacceptable. For a historian, presumably, the history of the Standard Model is to be evaluated in the same terms as the history of capitalism or Christianity: there are many reasons why a cause triumphed as and when it did, and the importance of such factors can be evaluated, but the historian cannot allow `right on its side' as one of them. Pickering swiftly disowns the `naive realism' of scientific accounts, in which the discovery of truth proceeds step by step, as being philosophically untenable. He will not allow reality to theoretical constructs - he repeatedly refers to quarks as being `invented' rather than `discovered'. For instance, he describes how the interpretation of the J / as a charm-anticharm bound state had problems. Physicists treated the shortcomings of the charm explanation (the sensationally long lifetime, some unexpected masses, and the lack of strange particles at higher energies) as interesting problems capable of resolution (the first, as it turned out, by theory and the latter two by experiment). There was an alternative interpretation of the particle as a coloured state. This also had shortcomings: it predicted charged versions of the J / , which were not seen, and this was used as a reason for the theory's rejection. Experimenters accordingly pursued a charm-based strategy, and eventually found what they sought. The author claims `it is impossible to say what would have happened if experimenters had pursued the predictions of colour with the same tenacity they devoted to charm' (page 276). Here one has to disagree. There would have been no discoveries that confirmed colour. Eventually the search would have stopped and the theory would have withered. The scientists would agree that the charm/colour decision was a matter of judgement. They would use words like `elegance' and `simplicity' to explain the provisional preference for the former over the latter, and they would certainly mention Ockham's razor. And they would say that subsequent developments showed they had backed the right horse. Again, Pickering contends that the reason the E122 (Prescott et al ) SLAC result was accepted, and the conflicting Oxford and Seattle results were rejected, was not due to the agency of the data but to a choice made by physicist. In this he is surely correct. He also contends that this choice was based on the fact that the former agreed with the social and conceptual apparatus of the `new physics' standard model whereas the latter did not. Here his argument is flawed. The atomic physics experiments could be incorporated into the standard model framework reasonably easily, by, for example, the addition of a second Z boson whose effects cancelled those of the first (and it is these theories, not the experimental results, that are the `mutants' referred to by Coleman in the passage quoted on page 291, whose slaying by the Prescott result led to its being known as the `SLAC massacre'.) This is, in fact, the reissue of a book published in 1984. As it covers the discovery of the W and the Z bosons, the 16 elapsed years do little damage to its validity as a history of the standard model. Apart from obvious historical matters (the success of LEP and the SLC, the failure of Isabelle, the end of Russia as a major player and the emergence of Japan), the most striking anomaly today is the prominence given to SU(5) and the absence of any mention of SUSY. It would also be very interesting to know what Pickering makes of the recent rebirth of interest in Regge theory at Hera. Much about the book is excellent.The science is accurate, the explanations are brilliantly concise. Following the tradition of Gibbon, even the footnotes are highly readable. The account is thorough - the author has really done his homework on the primary sources and has interviewed many of the people involved. He captures the way things actually were - the puzzlement over the lack of kaons from charm, the disquiet over the puzzling atomic physics experiments, and the surprise that our confirmation of QCD predictions about the collimation of jets produced in electron-positron annihilation should be hailed in the press as `the discovery of the gluon'. But his overall epistemology merely highlights the singular uselessness of philosophy when applied to physics.