ASTAROTH: A novel technique for dark matter direct detection with Na(Tl) crystals at cryogenic temperatures

The DAMA experiment has a long-standing claim for dark matter detection with the use of NaI(Tl) scintillating crystals. The ASTAROTH project plans to improve the physics reach of this technology with the same target material, allowing a larger sensitivity to the expected annual modulation signal with respect to the present-generation detectors. In fact, it would lower the detection energy threshold, making it possible to explore for the first time the recoils in the unprobed sub-keV region. This can be accomplished by cooling the system to cryogenic emperature and reading all the crystal surfaces with silicon photomultipliers. These sensors exhibit a lower dark count noise than photomultiplier tubes at T < 150 K and a higher collection efficiency. Scintillating liquid argon (T = 87 K) will surround the crystal, providing cooling power and acting as veto. We present here a first characterization of the crystal conducted in 2021 at LASA (Milano) with radioactive gamma sources as well as the details of the innovative cryogenic chamber under construction that will expand the temperature range to be explored in the near future.