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

On non hadronic origin of high energy neutrinos

Some of the non hadronic interactions, such as the \eta resonance formation in the \gamma \gamma interactions and the muon pair production in the e\gamma interactions, are identified as possible source interactions for generating high energy neutrinos in the cosmos.Comment: 9 pages, 1 figure, talk given at First NCTS Workshop on Astroparticle Physics, 6-9 December, 2001, Kenting, Taiwan (to appear in its proceedings edited by H. Athar, Guey-Lin Lin, and K.-W. Ng

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.Comment: 8 pages, 4 figures, invited talk given at CosPA 2003, 13-15 Nov, 2003, Taipei, Taiwa

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.Comment: 4 pages, 3 figures, talk given at 12th International Symposium on Very High Energy Cosmic Ray Interactions (XII ISVHERCI), 15-20 July, 2002, Geneva, Switzerland [to appear in its proceedings to be published by Nucl. Phys. B (Proc. Suppl.)

Recent status of the understanding of neutrino-nucleus cross section

In this work we have presented current understanding of neutrino-nucleon/nucleus cross sections in the few GeV energy region relevant for a precise determination of neutrino oscillation parameters and CP violation in the leptonic sector. In this energy region various processes like quasielastic and inelastic production of single and multipion production, coherent pion production, kaon, eta, hyperon production, associated particle production as well as deep inelastic scattering processes contribute to the neutrino event rates.Comment: 9-Pages, 4-figures, Talk given at DAE-HEP Symposium held at Delhi University, 12-16 December, 201