Test and Simulation of a LYSO+APD matrix with a tagged Photon Beam from 40 to 300 MeV

Abstract

Understanding the energy resolution terms for LYSO based calorimeters with APD readout at low energy (< 500 MeV) is relevant both for the completion of the KLOE-2 experiment, at DAΦNE, and for the design of the Mu2e calorimeter. In this work, we present a dedicated comparison between experimental data, taken in 2011 at the MAMI tagged photon beam facility with a crystal matrix prototype, and a full Geant-4 simulation of this detector. The crystal prototype matrix consisted of 9 2×2 × 15 cm3 LYSO crystals read-out by 10×10 mm2 Hamamatsu avalanche photodiodes (APD) surrounded by 8 PbWO4 crystals read-out by Bialkali photomultipliers for outer leakage recovery granting a total transverse coverage of 3 Rm. An energy resolution of ∼5.4% at 100 MeV has been achieved. A fit to the energy dependence of the resolution provides the following parametrization: σE/E = 2.1%/E1/4 ⊕ 3.6%, where the sum is in quadrature. The noise term is completely negligible as expected by the reduced level of the electronic noise achieved. The constant term is still leakage dominated.