Beam tests of a high resolution silicon vertex detector system with VLSI readout

The authors report a study of the resolution and tracking fidelity of a detector system using the LBL-designed SVX-D custom CMOS silicon readout chip in a random-switching mode suited to fixed target experiments. The system was composed of eight Hamamatsu DC-coupled silicon detectors combined with three stations of proportional wire chambers (PWCs) to make a multiparticle spectrometer. Interactions of 350-GeV pions in a 1-cm Al target as well as the single particle response to beam tracks are reported. The experiment gave a realistic test of the high-precision vertex detector. Interaction studies show that high efficiency for finding primary event vertices can be obtained based on combined information from downstream PWCs and fine-pitch silicon detectors. The SVX chip works extremely well for fixed target applications. Its intrinsic noise level is low and the sparsification allows high hardware efficiency and minimal extra data in the events. The system reliability and resolution are extremely high, as needed for experiments in which tracking failures produce serious backgrounds for the physics of interest