Enhanced signal of astrophysical tau neutrinos propagating through Earth

Earth absorbs νₑ and ν_μ of energies above about 100 TeV. As is well known, although ν_τ will also disappear through charged-current interactions, the ν_τ flux will be regenerated by prompt tau decays. We show that this process also produces relatively large fluxes of secondary νₑ and ν_μ, greatly enhancing the detectability of the initial ν_τ. This is particularly important because at these energies ν_τ is a significant fraction of the expected astrophysical neutrino flux, and only a tiny portion of the atmospheric neutrino flux.