Beam test of a DIRC-barrel-segment for the PANDA Experiment

R. Hohler1,2, D. Dutta†1, D. Lehmann1, K. Peters1,2, B. Roy‡1, G. Schepers1, C. Schwarz1, J. Schwiening1, C. Sfienti§ 1, and A. Vañó Viñuales3 1GSI, Darmstadt, Germany; 2Goethe Universität Frankfurt, Germany; 3Universitat de les Illes Balears, Spain Particle identification (PID) for hadrons and leptons over a large range of solid angles and momenta is an essential requirement for meeting the physics objectives at the PANDA detector. The charged PID in the barrel section of the target spectrometer [1] has to work in a strong magnetic field of B = 2 T. Additionally, it cannot take too much radial space, since it is surrounded by an electromagnetic calorimeter which should be kept small in volume. The detection of momenta up to 3.5 GeV/c can be performed by the Detection of Internally Reflected Cherenkov (DIRC) 1 light as realized in the BaBar detector [2, 3]. Particles in the angular range of 22◦ − 140◦ are relatively slow, so that one can use materials with high refraction indices favoring the internal reflection of photons. The lower momentum threshold of kaons producing Cherenkov light is as low as p = 460 MeV/c for an refractive index of n = 1.47. A prototype of a segment of this counter was tested in a 2 GeV test beam with protons in September 2009. The setup is a radiator coupled to an expansion box with photon detection on its back. The readout electronics operate in close distance to the photon detector and send the data by network to the backend computers.