Characterization of sensor modules for the CMS Barrel Timing Layer at the HL-LHC

The CMS detector is undergoing an extensive upgrade program to prepare for the challenging conditions of the High-Luminosity LHC starting in 2029. In particular, a new timing detector will measure minimum ionizing particles with a time resolution of 30–60 ps. The technology selected for the central part of the detector, the Barrel Timing Layer, consists of scintillating crystals of lutetium yttrium oxyorthosilicate doped with cerium (LYSO:Ce) read out with silicon photo-multipliers. A detailed characterization of several sensor modules, consisting of sixteen-channel crystal arrays coupled to a pair of Silicon Photomultiplier (SiPM) arrays, will be presented. The results represent the first thorough investigation of the performance of modules made with crystals and SiPMs of different geometries characterized with radioactive sources.