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H. Athar

Publications and source records attributed to H. Athar.

At least 19 recordsLinked to original sources
arXiv2006

The intrinsic and oscillated astrophysical neutrino flavor ratios

The pp interactions taking place in the cosmos around us are a source of the astrophysical neutrinos of all the three flavors. In these interactions, the electron and the muon neutrinos mainly come from the production and the decay of the π^{\pm} mesons, whereas the tau neutrinos mainly come from the production and the decay of the D^{\pm}_{S} mesons. We estimate the three intrinsic neutrino flavor ratios for 1 GeV < E < 10^{12} GeV in the pp interactions and found them to be 1 : 2 : 3\times 10^{-5}. We study the effects of neutrino oscillations on these intrinsic ratios. We point out that the three ratios become 1 : 1 : 1 if L(pc)/E(GeV)> 10^{-10} in the presence of neutrino oscillations, where L is the distance to the astrophysical neutrino source in units of parsecs.

hep-ph↗
arXiv2005

On the Prospects of Tau Neutrino Astronomy in Gev Energies and Beyond

We point out the opportunity of tau neutrino astronomy for neutrino energies of the order of 10 GeV to 10$^{3}$ GeV. In this energy range, it is demonstrated that the flavor dependence in the background atmospheric neutrino flux leads to drastically different prospects between the observation of astrophysical muon neutrinos and that of astrophysical tau neutrinos. Taking the galactic-plane neutrino flux as a targeted astrophysical source, we found that the galactic-plane tau neutrino flux dominates over the atmospheric tau neutrino flux for neutrino energies beyond 10 GeV. Hence the galactic-plane can in principle be seen through tau neutrinos with energies greater than 10 GeV. In a sharp contrast, the galactic-plane muon neutrino flux is overwhelmed by its atmospheric background until the energy of $10^{6}$ GeV.

hep-ph↗
arXiv2005

Tau Neutrino Astronomy in GeV Energies

We point out the opportunity of the tau neutrino astronomy for the neutrino energy E ranging between 10 GeV and 10^3 GeV. In this energy range, the intrinsic tau neutrino production is suppressed relative to the intrinsic muon neutrino production. Any sizable tau neutrino flux may thus arise because of the ν_μ\to ν_τ neutrino oscillations only. It is demonstrated that, in the presence of the neutrino oscillations, consideration of the neutrino flavor dependence in the background atmospheric neutrino flux leads to the drastically different prospects between the observation of the astrophysical muon neutrinos and that of the astrophysical tau neutrinos. Taking the galactic-plane neutrino flux as the targeted astrophysical source, we have found that the galactic-plane tau neutrino flux dominates over the atmospheric tau neutrino flux for E > 10 GeV. Hence, the galactic-plane can at least in principle be seen through the tau neutrinos with energies just greater than 10 GeV. In a sharp contrast, the galactic-plane muon neutrino flux is overwhelmed by its atmospheric background until E > 10^6 GeV.

hep-ph↗
arXiv2004

Three neutrino flavor oscillations and the atmospheric tau neutrinos

Downward going atmospheric tau neutrino flux is estimated in the presence of three neutrino flavor oscillations for 1 GeV < E < 10^3 GeV. The relative differences between the three and purely two neutrino flavor oscillations are elaborated. As an implication, the downward going atmospheric tau neutrino flux is compared with the galactic plane tau neutrino flux that is also estimated in the presence of three neutrino flavor oscillations. It is pointed out that the galactic plane tau neutrino flux dominates over the downward going atmospheric tau neutrino flux until E \sim 10 GeV.

hep-ph↗
arXiv2004

GeV to TeV astrophysical tau neutrinos

Neutrinos with energy greater than GeV are copiously produced in the p(A,p) interactions occurring in several astrophysical sites such as (i) the earth atmosphere, (ii) our galactic plane as well as in (iii) the galaxy clusters. A comparison of the tau and mu neutrino flux in the presence of neutrino oscillations from these three representative astrophysical sites is presented. It is pointed out that the non-atmospheric tau neutrino flux starts dominating over the downward going atmospheric tau neutrino flux for neutrino energy E as low as 10 GeV. This energy value is much lower than the energy value, E \geq 5\times 10^4 GeV, estimated for the dominance of the non-atmospheric mu neutrino flux, in the presence of neutrino oscillations. Future prospects for possible observations of non-atmospheric tau neutrino flux are briefly mentioned.

hep-ph↗
arXiv2004

Atmospheric and galactic tau neutrinos

Neutrinos with energy greater than GeV are copiously produced in the p(A,p) interactions occurring in the earth atmosphere and in our galactic plane. A comparison of the tau and mu neutrino flux in the presence of neutrino oscillations from these two astrophysical sites is presented. It is pointed out that the galactic plane tau neutrino flux dominates over the downward going atmospheric tau neutrino flux at much lower energy value than that for the dominance of the mu neutrino flux from these two sites. Future prospects for possible observations of galactic tau neutrino flux are also briefly mentioned.

hep-ph↗
arXiv2003

The high-energy galactic tau neutrino flux and its atmospheric background

We compare the tau neutrino flux arising from the galaxy and the earth atmosphere for $10^{3} \leq E/{GeV} \leq 10^{11}$. The intrinsic and oscillated tau neutrino fluxes from both sources are considered. We find that, for $E\geq 10^3$ GeV, 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 comment on the prospects for observing these high-energy tau neutrinos.

astro-ph↗
arXiv2003

High energy tau neutrinos: production, propagation and prospects of observations

High energy tau neutrinos with energy greater than several thousands of GeV may be produced in some astrophysical sites. A summary of the intrinsic high energy tau neutrino flux estimates from some representative astrophysical sites is presented including the effects of neutrino flavor oscillations. The presently envisaged prospects of observations of the oscillated high energy tau neutrino flux are mentioned. In particular, a recently suggested possibility of future observations of Earth-skimming high energy tau neutrinos is briefly discussed.

hep-ph↗
arXiv2003

Mixed high energy neutrinos from cosmos

Production of the expected high energy neutrino flux with energy greater than tens of thousands of GeV in some astrophysical sites such as the galactic plane as well as the centers of some distant galaxies is reviewed. The expected changes in these neutrino fluxes because of neutrino oscillations during their propagation to us are described. Observational signatures for these neutrino fluxes with and without neutrino oscillations are discussed.

hep-ph↗
arXiv2003

The energy spectrum of tau leptons induced by the high energy Earth-skimming neutrinos

We present a semi-analytic calculation of the tau-lepton flux emerging from the Earth, induced by the incident high energy neutrinos interacting inside the Earth for $10^{5} \leq E_ν/{\rm GeV} \leq 10^{10}$. We obtain results for the energy dependence of the tau-lepton flux coming from the Earth-skimming neutrinos, because of the neutrino-nucleon charged-current scattering as well as the resonant $\barν_e e^-$ scattering. We illustrate our results for several anticipated high energy astrophysical neutrino sources such as the AGNs, the GRBs, and the GZK neutrino fluxes. The tau lepton fluxes resulting from rock-skimming and ocean-skimming neutrinos are compared. Such comparisons can render useful information for the spectral indices of incident neutrino fluxes.

astro-ph↗
arXiv2002

Some aspects of neutrino astrophysics

Selected topics in neutrino astrophysics are reviewed. These include the production of low energy neutrino flux from cores of collapsing stars and the expected high energy neutrino flux from some other astrophysical sites such as the galactic plane as well as the center of some distant galaxies. The expected changes in these neutrino fluxes because of neutrino oscillations during their propagation to us are described. Observational signatures for these neutrino fluxes with and without neutrino oscillations are discussed.

hep-ph↗
arXiv2002

High Energy Astrophysical Tau Neutrinos: The Expectations

Aspects related to production, propagation and prospects for observationsof high energy astrophysical tau neutrinos originating from some representativeextra terrestrial sources such as atmosphere of earth, our galactic plane as well as possibly from distantsites of gamma ray bursts in the energy range 10^3 < E\GeV < 10^11 are reviewed.

hep-ph↗
arXiv2002

High energy astrophysical neutrinos

High energy neutrinos with energy typically greater than tens of thousands of GeV may originate from several astrophysical sources. The sources may include, for instance, our galaxy, the active centers of nearby galaxies, as well as possibly the distant sites of gamma ray bursts. I briefly review some aspects of production and propagation as well as prospects for observations of these high energy astrophysical neutrinos.

hep-ph↗
arXiv2002

On non hadronic origin of high energy neutrinos

Some of the non hadronic interactions, such as the ηresonance formation in the γγinteractions and the muon pair production in the eγinteractions, are identified as possible source interactions for generating high energy neutrinos in the cosmos.

hep-ph↗
arXiv2002

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\cdot 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.

hep-ph↗
arXiv2002

Neutrino spin-flip effects in active galactic nuclei

We study the effects of neutrino spin-flip in the magnetic field, B_{AGN}, of active galactic nuclei (AGN) for high-energy neutrinos (E > 10^{6} GeV) originating from AGN induced by an interplay of the violation of equivalence principle parameterized by $Δf$ and the twist in B_{AGN}. We point out that a conversion effect may exist for $Δf \sim 10^{-34} (δm^{2}/10^{-5} eV^{2})$ independent of gravity mixing angle. Observational consequences for this conversion effect are discussed.

hep-ph↗
arXiv2001

Implications of $\barν_{e}e^{-}\to W^{-}γ$ for high-energy $\barν_e$ observation

Absorption of high-energy $\barν_e$ over electrons above the W boson production threshold is reexamined. It is pointed out that, in the case of photon emissions along the direction of incident high-energy $\barν_e$, the kinematically allowed average energy carried by the final state hard photon can be $\leq 1%$ of the incident $\barν_e$ energy above the W boson production threshold. The differential energy spectrum for the final state hard photon is calculated. We also discuss implications of our results for the prospective search of high-energy $\barν_e$ through this final state hard photon.

hep-ph↗