Experiments at the DORIS e+e- collider at DESY 1977-92

After the discovery of the upsilon-particles at the Fermi Lab towards the end of 1977, a completely new group was formed at DESY to study in more detail the properties of these particles, which at that time was only possible at the electron-positron storage ring DORIS. I was invited to participate in this experiment and, together with a student of mine, we were the only foreign university representatives in this collaboration. The measurements were performed with the already existing Double Arm Spectrometer DASP. This apparatus consisted of a non-magnetic detector covering only 50% of the total solid angle and, on each side of the beam line, two magnetic spectrometers at 90o.

In taking over this old detector we had to bring it into renewed operation and because the previous users left insufficient documentation of the analysis package we had to rewrite essentially all programs for this purpose. Nevertheless we were able to publish proof of the existence of the upsilon ground state already in May 1978, and for the first excited state in August the same year. The parameters for the resonances were determined and, from the measured widths of these states, it could be concluded that the upsilon particles consisted of a bound bottom quark-antiquark pair.

Already in 1978 we started to plan a universal detector , ARGUS, which would be better suited for a more detailed study of the upsilon particles and the properties of the b quarks. As part of these plans DORIS was upgraded to reach beyond the threshold for the production of mesons with b quantum numbers.

In 1982 the construction of ARGUS was finished and after a short running-in period the detector proved to work beyond our expectations. Since then the experiment has produced a vast number of interesting data covering a broad spectrum of physics topics such as upsilon spectroscopy, B-meson physics, the production and decay of charmed particles, tau-lepton studies, two-photon physics and the search for exotic particles. Some of the most important results are the study of the nature of b-quarks through the spectroscopy of their bound states, the first analysis of gluon jets from upsilon-decays, the first measurement of B-Bbar mixing and the prediction of an unexpectedly high top-quark mass, the mass determination of the tau lepton and the bounds on the tau neutrino mass, the first observation of J/Psi decays of B-mesons and the observation of charmless B-decays.