Tau neutrino propagation and tau energy loss

Electromagnetic energy loss of tau leptons is an important ingredient for eventual tau neutrino detection from high energy astrophysical sources. Proposals have been made to use mountains as neutrino converters, in which the emerging tau decays in an air shower. We use a stochastic evaluation of both tau neutrino conversion to taus and of tau electromagnetic energy loss. We examine the effects of the propagation for monoenergetic incident tau neutrinos as well as for several neutrino power-law spectra. Our main result is a parameterization of the tau electromagnetic energy loss parameter $\beta$. We compare the results from the analytic expression for the tau flux using this $\beta$ with other parameterizations of $\beta$.