Towards large calorimeters based on Lanthanum Bromide or LYSO crystals coupled to silicon photomultipliers: A first direct comparison for future precision physics

Two very promising materials as the BrilLanCe (Cerium doped Lanthanum Bromide, LaBr3(Ce) and the LYSO (Lutetium Yttrium OxyorthoSilicate, Lu2(1−x) Y2x SiO5 (Ce)) coupled to Silicon photomultipliers (MPPC/SiPM) could represent an appealing option for the future calorimetry. The response of both LaBr3(Ce) and LYSO detectors having MPPC as photosensors have been studied via detailed Monte Carlo (MC) simulations. The impinging gammas are in the range of 50–100 MeV. The MC simulations are based on GEANT4, including the full electronic chain up to the waveform digitizer and finally the reconstruction algorithms. The results have been obtained are very promising. For a detector based on a (radius R = 4.45 cm, length L = 20.3 cm) LaBr3(Ce) crystal an energy resolution of σE/E[%]=2.3(1) and a timing resolution of σt[ps] = 35(1) have been predicted. The energy resolution can be further improved by using larger crystals (either R = 6.35 cm or R = 7.6 cm, L = 20.3 cm) approaching respectively a σE/E[%]=1.20(3) or a σE/E[%]=0.91(1). Detector based on LYSO crystal of similar size performs even better, thanks to the shorter LYSO Moliere radius compared to the LaBr3(Ce) one. For a detector based on a (R = 3.5 cm, L = 16 cm) LYSO crystal an energy resolution of σE/E[%]=1.7(1)% can be obtained, and that can be further improved using bigger crystals (R = 6.5 cm, L = 25 cm, σE/E[%]=0.74(1)%. Energy resolution approaching σE/E[%]=0.3(1)% can be addressed for both crystals with ultimate sizes (R = 20–23 cm, L = 17–32 cm), complemented by timing and position resolutions in the range of O(30) ps and O(a few mm) respectively. Such results put these future high energy calorimeters at the detector forefront at intensity frontiers.