High-accuracy 4D particle trackers with Resistive Silicon Detectors (AC-LGADs)

<!--HTML-->Future particle trackers will have to measure concurrently position and time with unprecedented resolutions, approximately 5 microns and 10 ps respectively. A promising good candidate are the AC-LGADs, silicon sensors of novel design, with internal gain and an AC-coupled resistive read-out to achieve signal sharing among pads. This design leads to a drastic reduction of read-out channels, has an intrinsic 100% fill factor, and adapts easily to any read-out geometry. I will present the challenges in the design, the signal formation, recent test results, and the reconstruction techniques that exploit the distributed nature of the signal, including machine learning.