Gargamelle (détecteur)

Gargamelle was a heavy liquid bubble chamber detector in operation at CERN between 1970 and 1979. It was designed to detect neutrinos and antineutrinos, which were produced with a beam from the Proton Synchrotron (PS) between 1970 and 1976, before the detector was moved to the Super Proton Synchrotron (SPS). In 1979 an irreparable crack was discovered in the bubble chamber, and the detector was decommissioned. It is currently part of the "Microcosm" exhibition at CERN, open to the public. Gargamelle is famous for being the experiment where neutral currents were discovered. Found in July 1973, neutral currents were the first experimental indication of the existence of the Z0 boson, and consequently a major step towards the verification of the electroweak theory. Gargamelle can refer to both the bubble chamber detector itself, or the high-energy physics experiment by the same name. The name itself is derived from a 16th-century novel by François Rabelais, The Life of Gargantua and of Pantagruel, in which the giantess Gargamelle is the mother of Gargantua. In a series of separate works in the 1960s Sheldon Glashow, Steven Weinberg, and Abdus Salam came up with a theory that unified electromagnetic and weak interaction between elementary particles—the electroweak theory—for which they shared the 1979 Nobel Prize in Physics. Their theory predicted the existence of the W± and Z0 bosons as propagators of the weak force. W± bosons have electric charge, either positive (W+) or negative (W−), the Z0, however, has no charge. Exchange of a Z0 boson transfers momentum, spin, and energy but leaves the particle's quantum numbers unaffected—charge, flavor, baryon number, lepton number, etc. Since there is no transfer of electric charge, the exchange of a Z0 is referred to as "neutral current". Neutral currents were a prediction of the electroweak theory. In 1960 Melvin Schwartz proposed a method of producing an energetic neutrino beam. This idea was used by Schwartz and others in an experiment in 1962 at Brookhaven, which demonstrated the existence of the muon and electron neutrino.