Sheldon Lee Glashow's 1979 lecture, Towards a Unified Theory: Threads in a Tapestry, recalls his 1961 construction: a photon, a massive neutral intermediary and a mixing angle. It also stresses its unresolved mass problem: symmetry-breaking masses had been inserted, rather than generated by the Higgs mechanism. Establishing the gauge structure and explaining the gauge boson masses were complementary steps.[ref]
Steven Weinberg's A Model of Leptons (1967) builds a spontaneously broken gauge theory for the electron-type leptons, using a scalar doublet to give masses while retaining a massless photon. It derives neutral and charged couplings and discusses neutrino-Electron scattering. Its closing question about renormalizability is explicitly unresolved; the paper is neither a proof of that property nor a complete treatment of quarks.[ref]
Abdus Salam's 1979 lecture, Gauge Unification of Fundamental Forces, describes his and Steven Weinberg's completion of the spontaneously broken formulation for leptons. He separates that construction from the subsequent establishment of renormalizability. Its role is to connect the mass mechanism with predictive neutral and charged couplings, not to identify a photographed event. The Gargamelle evidence subsequently tested the predicted neutral current.[ref]