Solar Active-Sterile Neutrino Conversion with Atomic Effects at Dark Matter Direct Detection Experiments

TL;DR

This paper develops a formalism to include atomic effects in solar neutrino interactions at dark matter detectors, showing these effects significantly influence the expected electron recoil signals and are crucial for interpreting experimental data.

Contribution

It introduces a second quantization formalism for bound and ionized electrons, enabling accurate inclusion of atomic effects in neutrino and dark matter scattering calculations.

Findings

Atomic effects significantly alter the differential cross section.

Including atomic effects is essential for low-energy electron recoil analysis.

Projected event rates at future experiments are provided based on this formalism.

Abstract

The recent XENON1T excess can be explained by the solar active-sterile neutrino conversion with bound electrons via light mediator. Nevertheless, the atomic effects are usually omitted in the solar neutrino explanations. We systematically establish a second quantization formalism for both bound and ionized electrons to account for the atomic effects. This formalism is of great generality to incorporate various interactions for both neutrino and dark matter scatterings. Our calculation shows that the change in the cross section due to atomic effects can have important impact on the differential cross section. It is necessary to include atomic effects in the low-energy electron recoil signal at dark matter direct detection experiments even for energetic solar neutrinos. With the best-fit values to the XENON1T data, we also project the event rate at PandaX-4T, XENONnT, and LZ experiments.