Nuclear and electron scattering by neutrinos and dark matter in condensed systems

Abstract

Low-threshold dark matter detectors, in particular cryogenic detectors based on dielectric materials, are among the best tools for probing sub-GeV dark matter masses. In the coming years detectors of this type will become sensitive to solar neutrino scattering. Previous work has shown that, for dark matter scattering at very low recoil energies, one must include collective excitations of the electrons in the solid. In this work, we have computed the collective excitations due to neutrino scattering on electrons and nuclei. We find the full electron-scattering response at leading order is captured by 5 structure factors and identify the leading component with the electron energy-loss function. Then, using silicon and germanium detectors as an example, we perform a dark matter sensitivity study and compute their respective neutrino floors. Lastly, we show that these detectors are sensitive to unexplored scenarios of beyond-Standard Model neutrino physics, within the exposure required to reach the neutrino floor.

Figures (10)

• Figure 1: Region of phase space integration for non-relativistic DM (the region above and to the left of the red line) and neutrino (green) compared to electron energy-loss function $\Im(-{1/\epsilon})$ of silicon (shaded blue). The visible part of this function corresponds to the plasmon resonance.
• Figure 2: Summary of neutrino-electron and neutrino-nucleus scattering rates in silicon (left) and germanium (right). The uncertainty bands on the nuclear recoils are derived from the different quenching models.
• Figure 3: Comparison of the Migdal effect rate for valence electrons via the dielectric function (from DFT calculations) versus the free atom approximation
• Figure 4: Models for nuclear recoil quenching in silicon (left) and germanium (right). In this work we use the Lindhard model as the upper bound and either the Sarkis model (germanium) or an empirical fit (silicon, from SuperCDMS:2023geu) as the lower bound.
• Figure 5: Neutrino-electron and neutrino-nucleus scattering rates in silicon (left) and germanium (right) in terms of liberated charge. The bands denote uncertainty due to the nuclear recoil quenching model.