Simulating Geomagnetic Deflections of Atmospheric Muons as a Background to Tau-Neutrino Detection by Balloon-Borne Cherenkov Telescopes

We investigate atmospheric muons acting as a possible background to detecting very-high-energy (VHE, >10 PeV) neutrinos via the earth-skimming technique due to their deflections in the geomagnetic field. In the Earth-skimming technique, the Earth converts a tau-neutrino into a tau-lepton, which can escape into the atmosphere and produce an EAS traveling upwards from the surface of the Earth. These EASs emit Cherenkov signals which can be observed as coming from below Earth's limb by a balloon in the upper atmosphere —or by a satellite in orbit. GeV-scale muons produced in cosmic ray-initiated EASs can mimic this signal as they deflect upwards in Earth's geomagnetic field. We studied this effect by developing a simulation framework to model muons in near-horizontal EASs as they interact in the International Geomagnetic Reference Field. We also include atmospheric interactions and Cherenkov production of muons as well as their subshowers after they decay. We used this framework to calculate the rate at which muons generate upwards-going Cherenkov signals observable by a telescope on a balloon at 33 km altitude. Our results indicate that these muon-induced Cherenkov signals are present, however, the intensities are below the threshold of current balloon-borne Cherenkov detectors.