Search for sub-GeV Dark Matter via Migdal effect with an EDELWEISS germanium detector with NbSi TES sensors

TL;DR

This paper reports on a search for sub-GeV dark matter particles using a cryogenic germanium detector with NbSi TES sensors, focusing on the Migdal effect to extend sensitivity to lower mass ranges.

Contribution

It demonstrates the use of NbSi TES sensors for low-threshold detection in dark matter searches, exploring new parameter space for low-mass dark matter particles.

Findings

Set new limits on dark matter cross-sections down to 10^{-29} cm^2.

Achieved a low energy threshold of 30 eVee with NbSi sensors.

Identified background as the main sensitivity limitation.

Abstract

The EDELWEISS collaboration reports on the search for Dark Matter (DM) particle interactions via Migdal effect with masses between $32$ MeV$\cdot$c$^{-2}$ to $2$ GeV$\cdot$c$^{-2}$ using a $200$ g cryogenic Ge detector sensitive to simultaneously heat and ionization signals and operated underground at the Laboratoire Souterrain de Modane in France. The phonon signal was read out using a Transition Edge Sensor made of a NbSi thin film. The detector was biased at $66$ V in order to benefit from the Neganov-Trofimov-Luke amplification and resulting in a resolution on the energy of electron recoils of $4.46$ eV$_{ee}$ (RMS) and an analysis threshold of $30$ eV$_{ee}$. The sensitivity is limited by a dominant background not associated to charge creation in the detector. The search constrains a new region of parameter space for cross-sections down to $10^{-29}$ cm$^2$ and masses between $32$ and $100$ MeV$\cdot$c$^{-2}$. The achieved low threshold with the NbSi sensor shows the relevance of its use for athermal-phonon sensitive devices for low-mass DM searches.