A Silicon-Based Cosmic Ray Telescope as an External Tracker to Measure Detector Performance

High-energy physics experiments at the high-intensity frontier place ever-greater demands on detectors, and in particular on tracking devices. In order to compare the performance of many possible small-size tracking prototypes, a high-resolution cosmic ray tracker may be used as an external track reference. We have constructed a telescope by assembling four spare ladders of the external layers of the Silicon Vertex Tracker of the BaBar experiment. This test facility, operating at INFN Sezione di Pisa, provides the detector under test with an external track with an intrinsic resolution of 15-30 mu m. The DAQ originally used in the BaBar experiment was replaced by custom-designed boards coupled with an acquisition front-end personal computer through commercial field-programmable gate array evaluation boards. We show that the facility is operative, and we present the performance in terms of tracking resolution and efficiency. A first device has been characterized, and some plots from the analysis demonstrating the telescope performance are shown.