Directional detection of light dark matter from three-phonon events in superfluid $^4$He

TL;DR

This paper proposes a novel method for detecting light dark matter using three-phonon emission in superfluid helium-4, enabling vertex reconstruction and background rejection through directional detection.

Contribution

It introduces a new detection signature involving three-phonon events in superfluid helium-4 for light dark matter, with detailed analysis and technological development.

Findings

Kinematic analysis of three-phonon emission enables dark matter interaction reconstruction.

Directional detection improves background rejection capabilities.

Differential distributions for the process are computed.

Abstract

We present the analysis of a new signature for light dark matter detection with superfluid $^4$He: the emission of three phonons. We show that, in a region of mass below the MeV, the kinematics of this process can offer a way to reconstruct the dark matter interaction vertex, while providing background rejection via coincidence requirements and directionality. We develop all the necessary technology to deal with such an observable, and compute the associated differential distributions.