Ultra-high energy cosmic neutrinos

Several cosmologically distant astrophysical sources may produce ultra-high energy cosmic neutrinos (E > 10^6 GeV) of all flavors above the atmospheric neutrino background. I study the effects of vacuum neutrino flavor mixing on this cosmic neutrino flux. Prospects for observations of these ultra-high energy cosmic neutrinos in large underwater/ice neutrino telescopes are also briefly discussed.Comment: 3 pages, latex, talk given at the 8th Asia Pacific Physics Conference (APPC2000), 7-10 August, 2000, Taipei, Taiwan (to appear in its proceedings

Neutrino conversions in cosmological gamma-ray burst fireballs

We study neutrino conversions in a recently envisaged source of high-energy neutrinos (E \geq 10^6 GeV), that is, 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.Comment: 16 pages, latex, one figure included as an eps file; improved and extended version of hep-ph/9901450 (to appear in Astroparticle Physics

Neutrino Conversions in Active Galactic Nuclei

I discuss the possibility of production of high energy cosmic neutrinos (E \geq 10^{6} GeV) in cores of active galactic nuclei and study some of the effects of neutrino mixing on their subsequent propagation. I also discuss the prospects for observations of these high energy cosmic neutrinos in new km^{2} surface area underwater/ice neutrino telescopes.Comment: 7 pages, Latex, 1 figure included with epsf, talk given at 9th Lomonosov Conference on Elemenatry Particle Physics, 20-26 September, 1999, Moscow, Russia [to appear in its proceedings edited by A. Studeniken

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.Comment: 17 pages, 5 figures (to appear in PLB

High Energy Cosmic Tau Neutrinos

I discuss the possibility of production of high energy cosmic tau neutrinos ($E \geq 10^{6}$ GeV) in an astrophysical site and study some of the effects of neutrino mixing on their subsequent propagation. I also discuss the prospects for observations of these high energy cosmic tau neutrinos through double shower events in new km$^{2}$ surface area under water/ice neutrino telescopes.Comment: 3 pages, Latex (uses espcrc2), 1 figure included with epsf, talk given at 6th International Workshop on Topics in Astroparticle and Underground Physics (TAUP 99), 6-10 September, Paris, France [to appear in its proceedings in Nucl. Phys. B (Proc. Suppl.) edited by M. Froissart, J. Dumarchez and D. Vignaud