Test beam characterization of sensor prototypes for the CMS Barrel MIP Timing Detector

The MIP Timing Detector will provide additional timing capabilities for detection of minimum ionizing particles (MIPs) at CMS during the High Luminosity LHC era, improving event reconstruction and pileup rejection. central portion detector, Barrel Layer (BTL), be instrumented with LYSO:Ce crystals Silicon Photomultipliers (SiPMs) providing a time resolution about 30 ps beginning operation, degrading to 50-60 end detector lifetime as result radiation damage. In this work, we present results obtained using 120 GeV proton beam Fermilab Test Beam Facility measure unirradiated sensors. A proof-of-concept sensor layout proposed barrel region MTD, consisting elongated crystal bars dimensions 3 x 57 mm$^3$ double-ended SiPM readout, is demonstrated. This design provides robust measurement independent impact point along bar. We tested different thickness (2, 3, 4 mm) geometry close reference coupled SiPMs manufactured by Hamamatsu Fondazione Bruno Kessler. various aspects influencing performance such thickness, properties (e.g. photon efficiency), angle are studied. 28 measured MIPs crossing mm thick bar, corresponding an MPV energy deposition 2.6 MeV, 22 4.2 MeV expected in BTL, matching target devices.