The NUCLEUS experiment aims for the first fully coherent detection of coherent elastic neutrino-nucleus scattering (CE$\nu$NS) at a new experimental site between the two 4 GWth reactor cores of the Chooz power plant. The signature of a CE$\nu$NS event will be a nuclear recoil at the 20 eV-scale inside a CaWO4 target crystal. At this energy scale, a reliable simulation of the signal and its background is crucial.
The recently started ELOISE project will provide reliable simulations of electromagnetic particle interactions in CaWO4 down to O(10eV). However, all standard simulation packages have higher applicability limits. Furthermore, even at this “high” energy, the accuracy is only assessed for few materials but not CaWO4. Within a time scale of four years, ELOISE plans to tackle this issue in a two-stage process: First, to evaluate the accuracy and second, if needed, to develop bespoken simulation code with increased accuracy.
In this contribution we motivate the necessity for reliable sub-keV simulations, identify the resulting challenges, outline ELOISE’s approach to overcome them and report the status of ongoing evaluation efforts.