Superheavy Dark Matter Candidates: Flux Limits, Multi-Scatter Signatures and the Exposure at Which Mass Stops Mattering

This study computes event rates and signatures for dark matter candidates with masses from 1e6 GeV to near the Planck mass. As mass rises at fixed local density, the number density and therefore the flux fall in inverse proportion, so single-scatter rates become negligible long before the Planck scale; the compensating signature is that a sufficiently strongly interacting heavy candidate scatters many times while crossing a detector, leaving a slow, straight, multiply-scattering track unlike any single recoil. The paper derives the mass at which the expected flux through a tonne-scale detector falls below one particle per year, and the cross-section range in which multi-scatter searches in large-volume detectors are the only available test. Density-bound screening is reported for each mass, and the bound grows as the square of the mass on each branch. All results are computed, not measured.