Looking for WIMPs through the neutrino fogs

TL;DR

This paper assesses the sensitivity limits of large xenon detectors for WIMP detection, highlighting the significant impact of neutrino backgrounds, and updates the exposure requirements for discovering or excluding various WIMP models.

Contribution

It provides a realistic simulation of neutrino backgrounds in xenon detectors and refines the exposure estimates needed for WIMP discovery or exclusion.

Findings

Neutrino backgrounds significantly limit WIMP detection sensitivity.

All zero hypercharge WIMPs can be excluded with 50 tonne-year exposure.

Large portions of hypercharged WIMP parameter space are accessible with current detector scales.

Abstract

We revisit the expected sensitivity of large-scale xenon detectors to Weakly Interacting Massive Particles (WIMPs). Assuming current primary noise sources can be mitigated, we find that with the present discrimination power between nuclear and electron recoils, the experimental sensitivity is limited not only by atmospheric neutrinos' nuclear recoils (''nuclear recoil neutrino fog'') but also by solar neutrinos' electron-recoil events (''electron recoil neutrino fog''). While this is known by experimentalists, it is often missed or misunderstood by theorists, and we therefore emphasize this effect. We set up a realistic detector simulation to quantify the contamination of the WIMP signal from both these neutrino backgrounds. We observe that the electron-recoil background remains significant even for signal rates exceeding those of atmospheric neutrinos, as predicted by most electroweak WIMP candidates. We update the projections for the required exposure to exclude/discover a given electroweak WIMP, streamlining the computation of their signal rates and uncertainties. We show that all of the real WIMPs with zero hypercharge can be excluded (discovered) with a 50 tonne year (300 tonne year) exposure. A similar exposure will allow to probe a large portion of the viable parameter space for complex WIMP with non-zero hypercharge.