The First Gauge Theory of Weak Interactions and the Prediction of Weak Neutral Currents

Abstract

The three theoretical and historical components of the Standard Model are the exact chiral gauge theory of weak interactions, electroweak unification, and the Higgs mechanism for spontaneous symmetry breaking. I put into historical perspective my 1958 invention of the first gauge theory of weak interactions, predicting weak neutral currents, and show how the fundamental differences between global and gauge symmetries and between partial flavour and exact gauge symmetries, emerged in the strong and weak interactions. Although renormalizability is necessary for theoretical consistency, electroweak unification was not necessary, in principle. An interesting difference appears between the $\sin^2{θ_W}=0$ limit of the electroweak theory and the original $SU(2)_W$ gauge theory of weak interactions. While the electroweak mixing angle might have had any value (including zero), historically the value $\sin^2{θ_W} \sim 0.3$ actually observed in weak neutral currents gave circumstantial support for the Standard Model and stimulated the search for $W-$ and $Z-$mesons.