Dark matter, light mediators, and the neutrino floor

TL;DR

This paper investigates how light mediators in dark matter interactions affect the ability of future direct detection experiments to distinguish dark matter signals from neutrino backgrounds, emphasizing the importance of a general EFT approach.

Contribution

It provides a classification scheme based on momentum dependence to evaluate the impact of light mediators on detection sensitivity and background discrimination.

Findings

Certain operators with light mediators produce spectra similar to neutrino backgrounds.

The similarity of spectra depends on the mediator mass, with different behaviors for mediators below or above 100 MeV.

Lower recoil energy thresholds improve the potential to distinguish dark matter signals from neutrino backgrounds.

Abstract

We analyze future direct data matter detection experiments using Effective Field Theory (EFT) operators with light, $\lesssim 100$ MeV mass mediators. We compare the nuclear recoil energy spectra from these operators to the predicted high energy solar neutrino spectrum. A set of operators that generate spectra similar to the neutrino background is identified, however this set is distinct from those that mimic the neutrino background for heavy, $\gtrsim 100$ MeV mass mediators. We outline a general classification scheme based on momentum dependence of the dark matter-nucleus interaction to determine how strong the discovery limit for a given operator saturates in the presence of the neutrino background. Our results highlight the benefit of considering a general theoretical framework regarding dark matter, and motivate continued experimental progress towards lower nuclear recoil energy thresholds.