[en] A new type of ring-imaging Cherenkov detector is being used for hadronic particle identification in the BABAR experiment at the SLAC B Factory (PEP-II). This detector is called DIRC, an acronym for Detection of Internally Reflected Cherenkov (Light). This paper will discuss the construction, operation and performance of the BABAR DIRC in detail

[en] The principles of the DIRC ring imaging Cherenkov technique are briefly explained and its choice for the BABAR detector particle identification system is motivated. A large scale prototype of the DIRC for the BABAR experiment is then described. Details of the design of this prototype and its test in a hadronic particle beam at the CERN-PS are presented, and results from various prototype and test configurations are given. For example, after correcting for geometrical acceptance and estimated collection effects, the number of photoelectrons was measured to be 146±1.8±9 cm^-1, for a track angle of 20 at zero photon transmission distance. The effective attenuation loss was measured to be 4.1±0.7% per meter of bar length, and the observed single photon resolution was 10.0±0.2 mrad. This performance is consistent with what was expected from earlier tests and Monte Carlo simulations, and will be fully adequate for the physics demands of the BABAR experiment. (orig.)

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