Experimental verification of the Salam-Weinberg theory

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Abstract
A review is given of the steps leading to the development of the Salam-Weinberg theory. The theory itself is defined and its relation to the general class of SU(2)*U(1) theories established. The discovery of weak neutral currents is described, as is the verification of the Glashow, Illiopoulos and Maiani quark coupling scheme in the discovery of charmed particles. Recent measurements of neutral current interactions of neutrinos are shown to lead to a unique set of quark couplings. The results of experiments on neutrino-electron scattering, when combined with data from the scattering of polarised electrons on deuterium, lead to a determination of the leptonic neutral current couplings. These couplings are consistent with data on weak effects in electron-positron collisions. The neutral current couplings thus derived favour a version of the SU(2)*U(1) theory with the Higgs mesons in doublets and quarks and leptons in right-handed singlets. In such a theory the data yield a value of sin2 theta w=0.233+or-0.009. The implications of this value for the grand unified theories of weak, electromagnetic and strong interactions are discussed.