A novel high-granularity crystal calorimeter

Abstract

Future electron-positron colliders, or Higgs factories, impose stringent requirements on the energy resolutions of hadrons and jets for the precision physic programs of the Higgs, Z/W bosons and the top quark. Based on the particle-flow paradigm, a novel highly granular crystal electromagnetic calorimeter (ECAL) has been proposed to address major challenges from the jet reconstruction and to achieve the optimal electromagnetic energy resolution of around 2-3%/√E(GeV) with the homogeneous structure. R&D efforts have been carried on to evaluate the requirements on the sensitive detector units and physics potentials of the crystal calorimeter concept within a full detector system. The requirements on crystals, photon sensors as well as readout electronics are parameterized and quantified in a full simulation model based on Geant4. Experiments including characterizations of crystals and silicon photomultipliers (SiPMs) have been followed to validate simulation results and optimize simulation parameters. Physics performance of the crystal ECAL has been studied with Higgs physics benchmarks using the particle-flow algorithm "ArborPFA". Progress has been made on optimizing the ArborPFA algorithm and parameters therein, leading to a significant improvement of the separation efficiency for close-by showers and jet reconstruction performance. For the new detector layout with long crystal bars arranged to be orthogonal to each other in two neighboring layers, a dedicated reconstruction software is also being developed to address major challenges on pattern recognition.