A semi-analytic calculation on the atmospheric tau neutrino flux in the GeV to TeV energy range

We present a semi-analytic calculation on the atmospheric tau neutrino flux in the GeV to TeV energy range. The atmospheric $\nu_{\tau}$ flux is calculated for the entire zenith angle range. This flux is contributed by the oscillations of muon neutrinos coming from the two-body $\pi, K$ decays and the three-body $\mu^{\pm}$ decays, and the intrinsic tau neutrino flux surviving the oscillations. The uncertainties in our calculations are discussed in detail. The implications of our result are also discussed.Comment: Revtex, 30 pages (including 13 figures); paper expanded and title slightly changed, to appear in Astroparticle Physic