Study of 3D calorimetry based on LYSO or LaBr3:Ce crystals for future high energy precision physics

Prototype calorimeters based on LYSO and LaBr3:Ce have been simulated, assuming different crystal sizes, from the currently available ones with a length of 16 cm and a diameter of 7 cm to an ultimate size of about 10 Moliere radii and 15 radiation lengths. These crystals are coupled to O(100) silicon photomultipliers for the available crystals. The response to 55 MeV photons was studied, a typical energy to be expected in charged lepton flavour violation experiments with muon decays. Simulations of the available size crystals show an energy resolution around 1.7% for LYSO and 2.5% for LaBr3:Ce as well as a timing resolution around 30 ps and a position resolution of O(5 mm) for both crystals. The simulations for the largest crystals indicated resolutions significantly below 1%, with clearly better values for LaBr3:Ce. Such performances pose these future calorimeters at the technology forefront and make them eligible candidates for upcoming experiments.