Experiments at the CERN ISR 1971-79

In 1971 I moved to Geneva to participate in an experiment at the ISR at CERN within the British-Scandinavian collaboration. The collision energies of the protons stored in the ISR were the highest in the world for a number of years and many fundamental results were obtained at this storage ring.

In an electron-nucleon deep inelastic scattering experiment at SLAC in 1969, the existence of electrically charged, point-like constituents within the nucleon was demonstrated. Following this discovery the first evidence for the strong interaction between the constituents was given in high energy proton-proton collisions at the ISR, which later led to the identification of the constituents as quarks and gluons. The scattering between individual constituents within the protons was expected to result in inclusive particle spectra with a fall-off in transverse momentum which is much slower than the approximately exponential behaviour that had been observed at small transverse momenta, a behaviour which was also observed.

In 1974 the group started an experiment at the ISR Split-Field-Magnet, which was a facility provided by CERN, consisting of a large magnet equipped with a large number of multiwire proportional chambers covering a large fraction of the solid angle. The spectrometer, which had been used in the previous experiment, was moved to the Split-Field Magnet as a complement to make particle identification at large angles possible. The aim of this experiment was to investigate the structure of the final states from high energy proton-proton collisions and, by selecting high pT-reactions, we expected to gain more detailed knowledge about collisions between the constituents of the colliding hadrons.