The electroweak interaction part of the Standard Model was formulated by Sheldon Glashow, Abdus Salam, and John Clive Ward in 1959, with their discovery of the SU(2)xU(1) group structure of the theory. In 1967, Steven Weinberg invoked the Higgs mechanism for the generation of the W and Z masses (the intermediate vector bosons responsible for the weak interactions and neutral-currents) and keeping the mass of the photon zero. The Goldstone and Higgs idea for generating mass in gauge theories was sparked in the late 1950s and early 1960s when a number of theoreticians (including Yoichiro Nambu, Steven Weinberg, Jeffrey Goldstone, François Englert, Robert Brout, G. S. Guralnik, C. R. Hagen, Tom Kibble and Philip Warren Anderson) noticed a possibly useful analogy to the (spontaneous) breaking of the U(1) symmetry of electromagnetism in the formation of the BCS ground-state of a superconductor. The gauge boson involved in this situation, the photon, behaves as though it has acquired a finite mass.