Tau Neutrino Flux Research Articles

Tracing very high energy neutrinos from cosmological distances in ice

Astrophysical sources of ultrahigh energy neutrinos yield tau neutrino fluxes due to neutrino oscillations. We study in detail the contribution of tau neutrinos with energies above PeV relative to the contribution of the other flavors. We consider several different initial neutrino fluxes and include tau neutrino regeneration in transit through the Earth and energy loss of charged leptons. We discuss signals of tau neutrinos in detectors such as IceCube, RICE and ANITA.

Secondary neutrinos from tau neutrino interactions in Earth

The energy dependence of "secondary" neutrinos from the process nutau->tau->numubar->mubar for two input tau neutrino fluxes (F^0_nu ~ 1/E_nu and 1/E_nu^2), assumed to have been produced via neutrino oscillations from extragalactic sources, is evaluated to assess the impact of secondary neutrinos on the upward muon rates in a km^3 detector. We show that the secondard fluxes are considerably suppressed for the steeper flux, and even for fluxes ~ 1/E_nu, the secondary flux will be difficult to observe experimentally.

Comparison of high-energy galactic and atmospheric tau neutrino flux

We compare the tau neutrino flux arising from the galaxy and the earth atmosphere for 10 3⩽ E/GeV⩽10 11. The intrinsic and oscillated tau neutrino fluxes from both sources are calculated. The intrinsic galactic ν τ flux ( E⩾10 3 GeV) is calculated by considering the interactions of high-energy cosmic-rays with the matter present in our galaxy, whereas the oscillated galactic ν τ flux is coming from the oscillation of the galactic ν μ flux. For the intrinsic atmospheric ν τ flux, we extend the validity of a previous calculation from E⩽10 6 GeV up to E⩽10 11 GeV. The oscillated atmospheric ν τ flux is, on the other hand, rather suppressed. We find that, for 10 3⩽ E/GeV⩽5×10 7, the oscillated ν τ flux along the galactic plane dominates over the maximal intrinsic atmospheric ν τ flux, i.e., the flux along the horizontal direction. We also briefly mention the presently envisaged prospects for observing these high-energy tau neutrinos.

High energy tau neutrinos

The intrinsic tau neutrino flux from cosmological and astrophysical sources has usually been considered negligible in comparison to the electron and muon neutrino fluxes. However, the inclusion of the tau neutrino component coming from hadronic decay at the source can significantly modify the tau neutrino spectrum expected at Earth. We report our results on the high energy tau neutrino production and its implications for the observation of high energy neutrino events.

Neutrino conversions in cosmological gamma-ray burst fireballs

We study neutrino conversions in a recently envisaged source of high energy neutrinos ( E≳10 6 GeV), i.e., in the vicinity of cosmological gamma-ray burst fireballs (GRB). We consider the effects of flavor and spin-flavor conversions and point out that, in both situations, a some what higher than estimated high energy tau neutrino flux from GRBs is expected in new km 2 surface area under water/ice neutrino telescopes.

Searching forνμ→ντoscillations with extragalactic neutrinos

We propose a novel approach for studying $\nu_\mu \to \nu_\tau$ oscillations with extragalactic neutrinos. Active Galactic Nuclei and Gamma Ray Bursts are believed to be sources of ultrahigh energy muon neutrinos. With distances of 100 Mpc or more, they provide an unusually long baseline for possible detection of $\nu_\mu \to \nu_\tau$ with mixing parameters $\Delta m^2$ down to $10^{-17}$eV$^2$, many orders of magnitude below the current accelerator experiments. By solving the coupled transport equations, we show that high-energy $\nu_\tau$'s, as they propagate through the earth, cascade down in energy, producing the enhancement of the incoming $\nu_\tau$ flux in the low energy region, in contrast to the high-energy $\nu_\mu$'s, which get absorbed. For an AGN quasar model we find the $\nu_\tau$ flux to be a factor of 2 to 2.5 larger than the incoming flux in the energy range between $10^2$ GeV and $10^4$ GeV, while for a GRB fireball model, the enhancement is 10%-27% in the same energy range and for zero nadir angle. This enhancement decreases with larger nadir angle, thus providing a novel way to search for $\nu_\tau$ appearance by measuring the angular dependence of the muons. To illustrate how the cascade effect and the $\nu_\tau$ final flux depend on the steepness of the incoming $\nu_\tau$, we show the energy and angular distributions for several generic cases of the incoming tau neutrino flux, $F_\nu^0 \sim E^{-n}$ for n=1,2 and 3.6. We show that for the incoming flux that is not too steep, the signal for the appearance of high-energy $\nu_\tau$ is the enhanced production of lower energy $\mu$ and their distinctive angular dependence, due to the contribution from the $\tau$ decay into $\mu$ just below the detector.

Tau neutrino fluxes from atmospheric charm

We present an evaluation of the atmospheric tau neutrino flux in the energy range between $10^2$ and $10^6$ GeV. The main source of tau neutrinos is from charmed particle production and decay. The $\nu_\tau N\to \tau X$ event rate for a detector with a water equivalent volume of 1 km$^3$ is on the order of 60-100 events per year for $E_\tau>100$ GeV, reducing to 18 events above 1 TeV. Event rates for atmospheric muon neutrino oscillations to tau neutrinos are also evaluated.