Design and Simulation Study of the Hadronic Calorimeter for the EicC Zero Degree Calorimeter

Abstract

The Zero-Degree Calorimeter (ZDC) at the proposed Electron-Ion Collider in China (EicC) is essential for detecting forward-going neutral particles and supporting the core nucleon spin and 3D imaging physics programs. In this work, a highly compact Spaghetti Calorimeter (SPACAL) architecture is proposed and optimized as the baseline design for the ZDC hadronic section. To systematically and quantitatively evaluate its physics capabilities, a comprehensive end-to-end Geant4 simulation framework was developed, integrating energy deposition, optical photon transport, photo-detection, and modeled front-end signal digitization. The optimized detector demonstrates excellent performance for neutron detection, achieving an energy resolution of $33.42\%/\sqrt{E/\mathrm{GeV}} + 1.47\%$ and a timing resolution of approximately 500 ps, outperforming the targeted specification. Furthermore, full-system simulations incorporating the upstream electromagnetic calorimeter yield a sub-centimeter transverse position resolution. Moreover, topological shower shape analysis across the full detector system provides robust particle identification (PID), with photon-neutron separation accuracy reaching over $99\%$ for high-energy incident particles. These quantitative results confirm that the SPACAL design fully satisfies the stringent operational and physics requirements of the EicC forward kinematic region.