On the Detectability of Light Dark Matter with Superfluid Helium

TL;DR

This paper proposes using superfluid helium's two-excitation process and high energy sensitivity to detect very light dark matter particles down to keV masses, surpassing previous methods by three orders of magnitude.

Contribution

It introduces a novel detection technique leveraging superfluid helium's two-excitation process for light dark matter detection, extending the mass reach significantly beyond existing approaches.

Findings

Detects dark matter down to keV mass range.

Achieves three orders of magnitude improvement over previous methods.

Proposes a coincidence mechanism to reduce backgrounds.

Abstract

We show that a two-excitation process in superfluid helium, combined with sensitivity to meV energy depositions, can probe dark matter down to the ~keV warm dark matter mass limit. This mass reach is three orders of magnitude below what can be probed with ordinary nuclear recoils in helium at the same energy resolution. For dark matter lighter than $\sim 100$ keV, the kinematics of the process requires the two athermal excitations to have nearly equal and opposite momentum, potentially providing a built-in coincidence mechanism for controlling backgrounds.