Light Dark Matter and Superfluid He-4 from EFT

TL;DR

This paper develops an effective field theory framework to analyze how superfluid helium-4 detectors respond to sub-GeV dark matter interactions, providing new insights into phonon emission processes and their suppression.

Contribution

It introduces an EFT approach for superfluid helium-4 to study dark matter interactions, including phonon lifetime calculations and suppressed two-phonon emission rates.

Findings

Phonon lifetime matches standard techniques, validating the EFT approach.

Two-phonon emission is significantly suppressed due to superfluid symmetry conservation.

Provides a theoretical basis for superfluid helium-4 dark matter detection experiments.

Abstract

We study the response of a He-4 detector to the interaction of sub-GeV dark matter using an effective field theory for the superfluid. We compute the lifetime of the phonon, which agrees with what known from standard techniques, hence providing an important check of the effective field theory. We then study the process of emission of two phonons, and show how its rate is much more suppressed than the phase space expectations; this is a consequence of the conservation of the current associated to the superfluid symmetries.