Undulating Dark Matter

TL;DR

This paper proposes that dark matter interactions can exhibit time-oscillating behavior due to microscopic physics, which can enhance detection strategies and provide insights into dark sector properties.

Contribution

It introduces the concept of undulating dark matter interactions driven by microscopic physics, exemplified by fermionic DM with an electric dipole moment influenced by an oscillating axion-like field.

Findings

Undulating scattering rates can improve dark matter detection sensitivity.

Time-dependent signals may reveal dark sector details.

Potential explanation for XENON1T excess via oscillating DM interactions.

Abstract

We suggest that an interplay between microscopic and macroscopic physics can give rise to dark matter (DM) whose interactions with the visible sector fundamentally undulate in time, independent of celestial dynamics. A concrete example is provided by fermionic DM with an electric dipole moment (EDM) sourced by an oscillating axion-like field, resulting in undulations in the scattering rate. The discovery potential of light DM searches can be enhanced by additionally searching for undulating scattering rates, especially in detection regions where background rates are large and difficult to estimate, such as for DM masses in the vicinity of 1 MeV where DM-electron scattering dominantly populates the single electron bin. An undulating signal could also reveal precious dark sector information after discovery. In this regard we emphasise that, if the recent XENON1T excess of events is due to light DM scattering exothermically off electrons, future analyses of the time-dependence of events could offer clues as to the microscopic origins of the putative signal.