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Abstract

For the HL-LHC phase, the calorimeter end-cap of the CMS detector will be upgraded with a High Granularity Calorimeter (HGCAL) with increased transverse and longitudinal granularity to cope with the expected pileup and radiation. In regions where radiation levels allow, the hadronic calorimeter will use scintillator tiles coupled to silicon photomultipliers (SiPM-on-tiles) as active materials. The HGCAL Tilemodule is the basic detector module of this region and can hold up to 144 SiPM-on-tile channels and two readout electronic chips (HGCROCs). Performances of various SiPM-on-tiles, including different SiPM sizes, tile sizes, scintillator materials, production technologies and irradiated SiPMs, were quantified at beam tests using $\SI{3}{GeV}$ electron beams at DESY-II. Further tests were conducted in temperature-controlled chambers to quantify the relationship between noise and leakage current passing through irradiated SiPMs on Tilemodules. The results from these tests were used in a model to obtain estimates of the signal-to-noise ratio (SNR) at the detector's end-of-life. Based on the estimates, changes to the final scintillator layout are proposed to obtain SNR>3 throughout the detector, including using smaller scintillator tiles in the frontmost layers and increasing the use of SiPMs with $3 \times \SI{3}{mm²}$ active area in the detector.