Discrimination between nuclear recoils and electron recoils by simultaneous detection of phonons and scintillation light

We have developed a detector, consisting of a cryogenic calorimeter with a scintillating crystal as an absorber, and a second calorimeter for the detection of scintillation light, both operated at 12 mK. Using a CaWO4 crystal with a mass of 6 g as the scintillating absorber, we have achieved a discrimination between nuclear recoils and electron recoils with a suppression factor of 99.7% at energies above 15 keV. This method will be applied for background rejection in the CRESST dark matter search (Cryogenic Rare Event Search with Superconducting Thermometers).