Search for sub-GeV dark matter via the Migdal effect with an EDELWEISS germanium detector with NbSi transition-edge sensors
E. Armengaud, Q. Arnaud, C. Augier, A. Benoı̂t, L. Bergé, J. Billard, A. Broniatowski, P. Camus, A. Cazes, M. Chapellier, F. Charlieux, M. De Jésus, L. Dumoulin, K. Eitel, J.-B. Filippini, D. Filosofov, J. Gascon, A. Giuliani, M. Gros, E. Guy, Y. Jin, A. Juillard, M. Kleifges, H. Lattaud, S. Marnieros, D. Misiak, X.-F. Navick, C. Nones, E. Olivieri, C. Oriol, P. Pari, B. Paul, D. V. Poda, S. Rozov, T. Salagnac, V. Sanglard, L. Vagneron, E. Yakushev, A. Zolotarova, Bradley J. Kavanagh
Abstract
The EDELWEISS collaboration reports on the search for dark matter particle interactions via Migdal effect with masses between $32\text{ }\text{ }\mathrm{MeV}\ifmmode\cdot\else\textperiodcentered\fi{}{\mathrm{c}}^{\ensuremath{-}2}$ to $2\text{ }\text{ }\mathrm{GeV}\ifmmode\cdot\else\textperiodcentered\fi{}{\mathrm{c}}^{\ensuremath{-}2}$ 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 $4.46\text{ }\text{ }{\mathrm{eV}}_{ee}$ (102.58 eV at 66 V) and an analysis threshold of $30\text{ }\text{ }{\mathrm{eV}}_{ee}$. 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 ${10}^{\ensuremath{-}29}\text{ }\text{ }{\mathrm{cm}}^{2}$ and masses between 32 and $100\text{ }\text{ }\mathrm{MeV}\ifmmode\cdot\else\textperiodcentered\fi{}{\mathrm{c}}^{\ensuremath{-}2}$. 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.