The PANDA experiment at the international accelerator Facility for Antiproton and Ion Research in Europe (FAIR), under construction near GSI, Darmstadt, Germany, will address fundamental questions of hadron physics. Excellent Particle Identification (PID) over a large range of solid angles and particle momenta will be essential to meet the objectives of the rich physics program. Charged PID for the PANDA target spectrometer will be provided by two innovative RICH counters using the DIRC (Detection of Internally Reflected Cherenkov light) technology.
The Barrel DIRC will cover the polar angle range of 22-140 degrees and cleanly separate charged pions from kaons for momenta between 0.5 GeV/c and 3.5 GeV/c with a separation power of at least 3 standard deviations (s.d.). The design is based on the successful BABAR DIRC and the SuperB FDIRC R&D with several important improvements to optimize the performance for PANDA, such as wider and shorter radiator bars, a spherical focusing lens system, fast timing, a compact fused silica prism as expansion region, and lifetime-enhanced Microchannel-Plate PMTs (MCP-PMTs) for photon detection.
The Endcap Disc DIRC (EDD) will separate pions from kaons with momenta up to 4 GeV/c and polar angles between 5 and 22 degrees with a separation power of 3 s.d. or more. The EDD consists of four optically isolated quadrants, each comprising a synthetic fused silica radiator plate of 2 cm thickness, focusing optics along the outer edge to convert the angle information into a position information, and a compact readout region. The intrinsic contribution of a chromatic error is reduced by an optical filter and an adapted photocathode. High-resolution MCP-PMTs will be used in connection with a fast ASIC-based readout to record events.
We will discuss the technical design of the two PANDA DIRC detectors and the results of the design validation using prototypes in hadronic particle beams at DESY and at CERN.