Design of hadronic calorimeter for DarkSHINE experiment

The sensitivity of the dark photon search through invisible decay final states in low-background experiments relies significantly on the neutron and muon veto efficiencies, which depend on the amount of material used and the design of the detector geometry. This paper presents the optimized design of the hadronic calorimeter (HCAL) used in the DarkSHINE experiment, which is studied using a GEANT4-based simulation framework. The geometry is optimized by comparing a traditional design with uniform absorbers to one that uses different thicknesses at different locations on the detector, which enhances the efficiency of vetoing low-energy neutrons at the sub-GeV level. The overall size and total amount of material used in the HCAL are optimized to be lower, owing to the load and budget requirements, whereas the overall performance is studied to satisfy the physical objectives.