The silicon tracking system of the CBM experiment at FAIR: Detector development and first in-beam applications

The CBM experiment will explore the QCD phase diagram at high net baryon densities and moderate temperatures. Its key component - the silicon tracking system STS - will reconstruct the trajectories of all charged particles created in collisions of heavy ions with a nuclear target, at typical beam energies of 25 GeV/nucleon. The central requirements of the STS are a particularly low-mass construction, imposed by the necessary momentum resolution of about 1%, as well as radiation hard sensors and a fast readout matching the high interaction rates of up to 10 MHz. First silicon microstrip detectors have been developed that are compatible with a thin modular structure of the STS tracking stations. The characterization of the detectors in the laboratory and in-beam tests are described. A demonstrator tracking station comprising a double-sided silicon detector prototype with 2 x 256 orthogonal strips of 50 μm pitch has been integrated into the beam tracker of the SVD-2 experiment at IHEP, Protvino, Russia. It was tested in a 50 GeV proton beam, yielding performance parameters as detector efficiencies, spatial resolution, cluster sizes and signal-to-noise ratios.