Particle identification by Cherenkov ring imaging

Developments and analysis techniques aiming at a best possible performance and understanding of the DELPHI RICH detector are the main subjects of this thesis. A high precision of the measured Cherenkov angle is crucial for a good particle identification. In order to achieve this for the DELPHI RICH detector, a careful calibration of its photon detectors and a precise alignment of its components has been performed. A charged particle produces typically 5 to 10 Cherenkov photons that are detected among numerous background signals from various sources. Most of these background signals are identified and removed. A generally good performance, essentially in agreement with the expectations, has been achieved. The implementation of the DELPHI RICH detector - one of the first large scale applications of the RICH technique - was a great challenge. Now, the DELPHI RICH detector has been fully operational since 1994 providing exceptionally pure and efficient identification of fast charged hadrons over nearly the full solid angle and a wide momentum range. A large number of important physics results relying on the RICH technique have been produced. One example is the first and unique measurement of the strange quark asymmetry at the Z0 peak. The measurements of the production rates of various types of hadrons in Z0 decays are other examples