First test beam measurement of the 4D resolution of an RSD pixel matrix connected to a FAST2 ASIC

This paper presents the measurement of the spatial and temporal resolutions of a Resistive Silicon Detector (RSD) pixel matrix read out by the FAST2 ASIC, a 16-channel fully custom amplifier developed by INFN Torino using a 110 nm CMOS technology. The test was performed at the DESY test beam facility with a 5 GeV/c electron beam. The RSD matrix is composed of seven 450 μm pitch pixels with cross-shaped electrodes for a total area of about 1.5 mm2. The position resolution reached is σx =14± 1 μm, approximately 3.5% of the pitch, and the temporal resolution is σt= 49 ± 6 ps. The work demonstrates that RSD sensors with cross-shaped electrodes achieve 100% fill factor and homogeneous resolutions over the whole matrix surface, making them a suitable choice for 4D tracking applications.