We present a semi-analytic calculation on the atmospheric tau neutrino flux
in the GeV to TeV energy range. The atmospheric ντ​ flux is calculated
for the entire zenith angle range. This flux is contributed by the oscillations
of muon neutrinos coming from the two-body π,K decays and the three-body
μ± 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