From the archive: July/August 1976

Tbilisi under the spell of Charm

The four quarks

About 800 physicists from many parts of the world attended the 18th International Conference on High Energy Physics, one of the biennial Rochester Conferences, in July 1976 in Tbilisi, the capital of the Georgian Soviet Socialist Republic. With events found at CERN, Fermilab, DESY and SPEAR, the consensus clearly was that particles bearing the new quantum number, charm, have been found. And the charm was not ‘hidden’, as in the J/ψ and ψ, but unashamedly ‘naked’, with characteristic decays involving leptons and strange particles and ‘exotic’ relationships between electric charge and strangeness. The discovery of charm confirms one of the more striking aspects of a theory developed over several years by many authors. One version, sometimes called the ‘standard model’, is based on the work of Weinberg and Salam and of Glashow, lliopoulos and Maiani. The theory is proving powerful in predicting phenomena such as neutral currents, and the understanding brought about by its unification of electric and weak forces has been compared to that achieved by Maxwell in unifying electricity and magnetism.

  • Compiled from text on p252 of CERN Courier July/August 1976.

Compiler’s note

With the second generation of quarks complete, the search was on for a third pair, predicted by Kobayashi and Maskawa in 1973 and named “top” and “bottom” by Haim Hartari. Lederman’s team at Fermilab found the bottom in 1977, but it took another 18 years before the 173 GeV/c2 top was finally discovered in 1995, also at Fermilab, 86,500 times heavier than the lightest up quark.