Performance of the Forward RICH detector system at DELPHI

One quarter of the Forward Ring Imaging Cherenkov (Forward RICH) detector has been installed and operated in the DELPHI experiment. The detector covers the forward-backward regions (15 degrees < theta <35 degrees ). Two radiator systems are used for particle identification in the momentum range up to 40 GeV/c, i.e., a liquid perfluorohexane and perfluorobutane gas. UV-photons with wavelengths from approximately 170 nm to approximately 200 nm (7.3-6.2 eV) are detected with high efficiency. The total active area of the photon detector is approximately 8 m/sup 2/.<
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