RICH prototype installed in one of the endcap sectors of the UA2 detector

These pictures show a small RICH detector with a gaseous radiator which was installed by an Athens-CERN-Uppsala-Wuppertal RICH Group in the UA2 experiment at the SPS experiment in 1985 to identify electrons from charm-quark decay. The measurements made with this RICH detector showed that the charm cross section did not rise as sharply as had been seen in other earlier experiments at lower energies at the ISR. The results of the earlier experiments were in contradiction with next-to-leading order QCD calculations at the time by P. Nason et al. where as the measurements made with this RICH detector in UA2 showed a cross-section at higher energies which was compatible with the next-to-leading order QCD calculations . The person on the photos is Allan Hallgren, Uppsala university. Spokesperson of this experiment was Tord Ekelöf, Uppsala University. The results of this experiment were reported by Ekelöf at the 1989 Moriond Conference and described in the CERN Courier. The final results were published in March 1990 in Physics Letter B. Links to the three articles are provided below.