Ultra-Heavy Dark Matter Search with Electron Microscopy of Geological Quartz

Despite ever-improving sensitivities, the simplest dark matter candidate particles have not been observed, motivating 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. The large interaction cross section of such ultra-heavy dark matter results in a distinctive and compelling signature: 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. In our work, we describe a high-resolution robust readout method based on electron microscopy, characterize the most favorable geological samples for this approach, and study its reach in a simple model of the dark sector.