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.