Modelling uncertainties for neutrino propagation using nuPyProp

The interaction probability of neutrinos with matter is low, owing to their charge neutrality and their weak interactions. This means they can travel cosmological distances to reach Earth largely unhindered, pointing back to their origins. Terrestrial, sub-orbital and orbital neutrino detectors can be designed to detect signals from the extensive air showers induced by charged leptons that come from ultra-high-energy neutrinos that have propagated through the Earth. An important feature in neutrino detection is the neutrino flux sensitivity of detectors. This flux sensitivity can be estimated using the nuPyProp simulation package, which propagates neutrinos (muon-neutrino, tau-neutrino) through the Earth to produce the corresponding charged leptons (muons and tau-leptons), which provides the input to extensive air shower simulations, such that what is in nuSpaceSim. In this talk, we quantify the uncertainties in the charged lepton exit probabilities and spectra that come from weak, electromagnetic and Earth density models using nuPyProp. Some of the parameters and models that we vary are: the local water depths, tau depolarization and photo-nuclear electromagnetic energy loss. The largest uncertainty comes from the photo-nuclear electromagnetic energy loss models, with some cases seeing a 20-50% difference between models. This work highlights the usefulness of nuPyProp in quantifying the small and large uncertainties due to input models in the determination of neutrino flux sensitivities of detectors.