High-accuracy 4D particle trackers with resistive silicon detectors (AC-LGADs)

Future particle trackers will have to measure concurrently position and time with unprecedented accuracy, aiming at 5 μm and a few 10s ps resolution respectively. A promising good candidate for such a task are the resistive AC-LGADs, solid state silicon sensors of novel design, characterized by an internal moderate gain and an AC-coupled resistive read-out to achieve signal sharing among pads. The sensor design leads to a drastic reduction in the number of read-out channels, has an intrinsic 100% fill factor, and adapts easily to any read-out geometry. This report describes the design challenges, the signal formation and recent test results obtained with the first prototypes. A part is also dedicated to the reconstruction techniques that exploit the distributed nature of the signal, including machine learning. An outlook to a future development for optimized read-out electrodes and electronics is also presented.