Search for sub-GeV dark matter via the Migdal effect with an EDELWEISS germanium detector with NbSi transition-edge sensors

The EDELWEISS collaboration reports on the search for dark matter particle interactions via Migdal effect with masses between 32 MeV center dot c-2 to 2 GeV center dot 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 eVee (102.58 eV at 66 V) and an analysis threshold of 30 eVee. 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 cm2 and masses between 32 and 100 MeV center dot c-2. The achieved low threshold with the NbSi sensor shows the relevance of its use for out-of-equilibrium phonon sensitive devices for low-mass dark matter searches.

Automated summary

The EDELWEISS collaboration conducted a search for dark matter particle interactions using a cryogenic Ge detector underground in France. The experimental results revealed limitations in sensitivity due to background interference. Constraints on certain parameters were obtained, providing guidance for further research. The experiment also demonstrated the importance of NbSi sensors in low-mass dark matter searches.