On the Existence of Low-Mass Dark Matter and its Direct Detection

TL;DR

This paper proposes a new low-mass dark matter candidate that has evaded detection so far and suggests optomechanical experiments, like nanoparticle interferometry, as promising methods for direct detection.

Contribution

It introduces a novel low-mass dark matter model and proposes a feasible experimental detection method using optomechanics technology.

Findings

Low-mass DM could have large interaction strength without current constraints.

Levitated nanoparticle interferometry can detect elastic collisions with DM particles.

The proposed method is within reach of current or near-future technology.

Abstract

Dark Matter (DM) is an elusive form of matter which has been postulated to explain astronomical observations through its gravitational effects on stars and galaxies, gravitational lensing of light around these, and through its imprint on the Cosmic Microwave Background (CMB). This indirect evidence implies that DM accounts for as much as 84.5% of all matter in our Universe, yet it has so far evaded all attempts at direct detection, leaving such confirmation and the consequent discovery of its nature as one of the biggest challenges in modern physics. Here we present a novel form of low-mass DM $\chi$ that would have been missed by all experiments so far. While its large interaction strength might at first seem unlikely, neither constraints from particle physics nor cosmological/astronomical observations are sufficient to rule out this type of DM, and it motivates our proposal for direct detection by optomechanics technology which should soon be within reach, namely, through the precise position measurement of a levitated mesoscopic particle which will be perturbed by elastic collisions with $\chi$ particles. We show that a recently proposed nanoparticle matter-wave interferometer, originally conceived for tests of the quantum superposition principle, is sensitive to these collisions, too.