Dark Matter, Dark Photon and Superfluid He-4 from Effective Field Theory

TL;DR

This paper explores how superfluid helium-4 detectors can constrain sub-GeV dark matter models mediated by dark photons, introducing a new effective field theory for photon-phonon interactions and assessing detection prospects.

Contribution

It develops the first low-energy effective field theory for photon-phonon interactions and evaluates superfluid helium-4's potential in detecting ultralight dark photon-mediated dark matter.

Findings

Superfluid helium-4 detectors can set competitive bounds for ultralight dark photons.

A new effective field theory for photon-phonon interactions is introduced.

Detection sensitivity is limited to ultralight vector mediators.

Abstract

We consider a model of sub-GeV dark matter whose interaction with the Standard Model is mediated by a new vector boson (the dark photon) which couples kinetically to the photon. We describe the possibility of constraining such a model using a superfluid He-4 detector, by means of an effective theory for the description of the superfluid phonon. We find that such a detector could provide bounds that are competitive with other direct detection experiments only for ultralight vector mediator, in agreement with previous studies. As a byproduct we also present, for the first time, the low-energy effective field theory for the interaction between photons and phonons.