TauRunner: A Monte Carlo for Very-High-Energy Tau Neutrino Propagation

The hunt for cosmogenic neutrinos is a target of next generation observatories: IceCube-Gen2, RNO, GRAND, POEMMA, and CHANT. In a recent publication, a novel detection strategy for these neutrinos has been put forward. This new technique relies on the observation of Earth-throughgoing tau neutrinos at PeV energies. By measuring the flux at this energy, we can indirectly observe the flux at EeV energies since these two are related by the cascading down of the neutrinos. However, such a link demands an accurate simulation of the VHE tau neutrino transport. TauRunner is a Python Monte Carlo (MC) package developed in 2019 that was intended for such effort, but contained some limitations. This contribution will present the newest version of this MC, which now incorporates all the neutrino flavors in the propagation as well as other features.