Detector-level assessment of alternative target nuclei for CEvNS experiments under realistic experimental conditions

Abstract

Coherent Elastic Neutrino-Nucleus Scattering (CEvNS) provides a sensitive probe of neutrino interactions at low momentum transfer, but its experimental observation is strongly constrained by detector-related effects such as energy threshold, resolution, noise, and event-selection criteria. In this work, we perform a detector-level assessment of CEvNS nuclear recoil observability under realistic experimental conditions, with particular emphasis on the role of detector response in shaping measurable recoil spectra. Using detailed Geant4-based simulations, CEvNS interactions are modeled for a set of alternative target nuclei spanning light to intermediate mass ranges. The true nuclear recoil energy distributions are propagated through a simplified yet realistic detector-response chain incorporating energy smearing, noise-induced fluctuations, threshold cuts, and veto-based event selection. We present a systematic analysis of recoil energy spectra before and after detector effects, response matrices linking true and reconstructed energies, and energy-dependent selection efficiencies. The results demonstrate that detector response effects significantly modify the observable CEvNS signal, particularly in the near-threshold region where most recoil events are concentrated. Differences in efficiency turn-on behavior and reconstructed energy distributions highlight the target-nucleus dependence of CEvNS observability under identical detector conditions. Rather than focusing on absolute event-rate predictions, this study emphasizes the relative impact of detector effects on signal accessibility and target performance. The presented framework provides a consistent methodology for evaluating and comparing prospective CEvNS target materials at the detector level, offering practical guidance for future low-threshold CEvNS experiments and detector design optimization.

Figures (4)

• Figure 1: True nuclear recoil energy spectra ($E_{\mathrm{true}}$) for the four target nuclei, produced under identical simulation settings. No detector-response model (smearing, threshold, veto, or additional analysis cuts) is applied in this figure; the distributions therefore represent the underlying kinematic recoil-energy spectra prior to detector effects.
• Figure 2: Measured nuclear recoil energy spectra ($E_{\mathrm{meas}}$) obtained after applying detector response effects, including energy resolution, threshold, and event selection cuts, for the four investigated CEvNS target nuclei: (a) boron (B), (b) magnesium (Mg), (c) titanium (Ti), and (d) zirconium (Zr). All spectra are shown under identical simulation and analysis conditions, illustrating how detector effects reshape the experimentally accessible recoil energy distributions depending on target mass.
• Figure 3: Detector response matrices mapping the generator-level (true) nuclear recoil energy, $E_{\mathrm{true}}$, to the reconstructed/measured recoil energy, $E_{\mathrm{meas}}$, after applying the common event selection for each target nucleus. The color scale encodes the event density in the ($E_{\mathrm{true}}$, $E_{\mathrm{meas}}$) plane, thereby visualizing resolution smearing, threshold-induced truncations, and analysis-driven distortions that shape the experimentally accessible recoil spectrum.
• Figure 4: Selection efficiency $\epsilon(E_{\mathrm{true}})$ for the four target nuclei, defined as $\epsilon(E_{\mathrm{true}})=N_{\mathrm{reconstructed}}/N_{\mathrm{generated}}$ in bins of the true nuclear recoil energy. Here, $N_{\mathrm{generated}}$ denotes the number of Monte Carlo events produced in a given $E_{\mathrm{true}}$ bin, and $N_{\mathrm{reconstructed}}$ represents the subset of events successfully reconstructed by the detector-response model. No additional analysis-level cuts beyond the detector threshold and veto model described in Section 2.3 are applied.Error bars reflect finite Monte Carlo statistics in each $E_{\mathrm{true}}$ bin.