Tau Neutrinos Underground:
Oscillations with Extragalactic
(with S. Iyer Dutta and M.H. Reno); Physical Review D62, 103054 (2000)
The appearance of high energy tau neutrinos due to
oscillations of extragalactic neutrinos
can be observed by
measuring the neutrino induced upward hadronic and electromagnetic showers
and upward muons. We evaluate quantitatively the tau neutrino regeneration
in the Earth for a variety of extragalactic neutrino fluxes.
Charged-current interactions of the upward tau neutrinos
below and in the detector, and the subsequent tau decay
muons or hadronic and electromagnetic showers. The background
for these events are muon neutrino and electron neutrino charged-current and
neutral-current interactions, where in addition to extragalactic neutrinos, we
consider atmospheric neutrinos.
We find significant signal to background
ratios for the hadronic/electromagnetic showers with
energies above 10 TeV to 100 TeV initiated by the
We show that
the tau neutrinos from point sources also have the potential for
discovery above a 1 TeV threshold. A
kilometer-size neutrino telescope has a very good chance of detecting
the appearance of tau neutrinos when both muon and hadronic/electromagnetic
showers are detected.