Geological quartz as a detector for ultra-heavy dark matter*

Despite extensive searches with ever-improving exclusion bounds, no dark matter candidate has yet been observed. This motivates searches for a wider range of possible dark sectors. Self-interactions within the dark sector could clump dark matter into heavy composite states with low number density, leading to a highly suppressed event rate for existing direct detection experiments. On the other hand, the large interaction cross section of such ultra-heavy dark matter results in a distinctive and compelling signature: macroscopically long, straight damage tracks as the composite dark matter passes through, and continuously scatters off, the surrounding matter. We propose using geologically old quartz samples as detectors for ultra-heavy dark matter. The advantage of this search strategy is two-fold: the age of the sample provides a large exposure time, and thus compensates for the ultra-heavy dark matter's low number density; and the unique geometry of the damage track serves as a high-fidelity background rejection tool. We present a high-resolution robust readout method based on electron microscopy, as well as a first characterization of the most favorable geological samples as detectors. We also demonstrate the reach of this search strategy in a simple QCD-like model of the dark sector.