For a summary of detector design considerations, see eRHIC dedicated detector design.
For full detector simulation in GEANT3/4, see eicroot framework.
For the ESIM simulation package, see ESIM. This page is outdated
Geant4: C++ detector simulation, successor to GEANT3. This page is outdated
For the FLUKA simulation package, see FLUKA. The FLUKA MC is not followed at this moment.
For the Detector Magnet Design see OPERA Tutorial