PBR sensitivity to boosted dark matter explanation for the KM3-230213A event

POEMMA-Balloon with Radio (PBR) is a hybrid fluorescence and optical Cherenkov telescope that is a pathfinder instrument for a future Probe Of Extreme Multi-Messenger Astrophysics (POEMMA), together with a radio instrument, to be flown on a super pressure balloon in Spring 2028. One of its science objectives is follow up of astrophysical event alerts via signals of tau decays in the atmosphere, sourced by Earth-skimming tau neutrinos. The recent report of the KM3NeT Collaboration's muon event with E μ=120+110-60 PeV sparked searches for beyond the standard model (BSM) physics explanations. Using a specific, boosted dark matter scenario which together with the KM3NeT observation, sets a scale for the fluence of boosted dark matter in this energy range, we assess the capabilities of PBR to constrain or discover such a source for a boosted dark matter energy spectrum above about 10 8 GeV. PBR has discovery potential for dark matter energies above 10 9 GeV, and depending on BSM input parameters, to dark matter energies as low as 1.5 times 10 8 GeV. While the analysis is focused on one BSM example, the methodology is applicable to any BSM physics that affects tau production in the Earth.