The making of the Standard Model
I have been asked to review the history of the formation of the Standard Model. It is natural to tell this story as a sequence of brilliant ideas and experiments, but here I will also talk about some of the misunderstandings and false starts that went alo
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I have been asked to review the history of the formation of the Standard Model. It is natural to tell this story as a sequence of brilliant ideas and experiments, but here I will also talk about some of the misunderstandings and false starts that went along with this progress, and why some steps were not taken until long after they became possible. The study of what was not understood by scientists, or was understood wrongly, seems to me often the most interesting part of the history of science. Anyway, it is an aspect of the Standard Model with which I am very familiar, for as you will see in this talk, I shared in many of these misunderstandings. I’ll begin by taking you back before the Standard Model to the 1950’s. It was a time of frustration and confusion. The success of quantum electrodynamics in the late 1940s had produced a boom in elementary particle theory, and then the market crashed. It was realized that the four-fermion theory of weak interactions had infinities that could not be eliminated by the technique of renormalization, which had worked so brilliantly in electrodynamics. The four-fermion theory was perfectly good as a lowest-order approximation, but when you tried to push it to the next order of perturbation theory you encountered unremovable infinities. The theory of strong interactions had a different problem; there was no difficulty in constructing renormalizable theories of the strong interactions like the original Yukawa theory but, because the strong interactions are strong, perturbation theory was useless, and one could do no practical calculations with these theories. A deeper problem with our understanding of both the weak and the strong interactions was that there was no rationale for any of these theories. The weak interaction theory was simply cobbled together to fit what experimental data was available, and there was no evidence at all for any particular theory of strong interactions. c 2003 by Steven Weinberg
R. Cashmore et al. (eds.), Prestigious Discoveries at CERN © Springer-Verlag Berlin Heidelberg 2003
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S. Weinberg
There began a period of disillusionment with quantum field theory. The community of theoretical physicists tended to split into what at the time were sometimes called, by analogy with atomic wave functions, radial and azimuthal physicists. Radial physicists were concerned with dynamics, particularly the dynamics of the strong interactions. They had little to say about the weak interactions. Some of them tried to proceed just on the basis of general principles, using dispersion relations and Regge pole expansions, and they hoped ultimately for a pure S-matrix theory of the strong interactions, completely divorced from quantum field theory. Weak interactions would somehow take care of themselves later. Azimuthal physicists were more modest. They took it as a working rule that there was no point in trying to understand strong interaction dynamics, and instead they studied the one sort of thing that could be used to make predictions without such understanding – princip
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