Particles or Primordial Black Holes: What Would Settle the Dark Matter Question

… more less Particles win if two targets see the same recoil spectrum or a haloscope sees a fixed-frequency line; black holes win with a merger below about 1 solar mass, which stars cannot make. Closing the \( 10^{17} \)–\( 10^{22} \) g window would retire PBHs as the bulk.