DIRC, the particle identification detector for BaBar

Beam test results obtained at the CERN PS are presented for a full prototype of the DIRC, the particle identification detector of the BaBar experiment at SLAC. Given the average number of observed photons per track and the measured single-photon angular resolution of 10.1 mrad, a 3σ πK separation up to 3.0 GeV/c is achieved. These results are in agreement with preliminary studies done during the conception of the project.