Ambiguity in source flux of high-energy cosmic/astrophysical neutrinos: Effects of bi-maximal mixing and quantum-gravity induced decoherence

Abstract

For high energy cosmic neutrinos Athar, Jezabek, and Yasuda (AJY) have recently shown that the existing data on neutrino oscillations suggests that cosmic neutrino flux at the AGN/GRB source, F(nu_e):F(nu_mu):F(nu_tau) approx 1:2:0, oscillates to F(nu_e):F(nu_mu):F(nu_tau) approx 1:1:1. These results can be confirmed at AMANDA, Baikal, ANTARES and NESTOR, and other neutrino detectors with a good flavor resolution. Here, we re-derive the AJY result from quasi bi-maximal mixing, and show that observation of F(nu_e):F(nu_mu):F(nu_tau) approx 1:1:1 does not necessarily establish cosmic neutrino flux at the AGN/GRB source to be F(nu_e):F(nu_mu):F(nu_tau) approx 1:2:0. We also note that if the length scale for the quantum-gravity induced de-coherence for astrophysical neutrinos is of the order of a Mpc, then independent of the MNS matrix, the Liu-Hu-Ge (LHG) mechanism would lead to flux equalization for the cosmic/astrophysical neutrinos.

Comments: Published version. A "Note Added" on (a) The reported ambiguity in the context of a two-doublet structure of the 4-neutrino mixing [L. Bento, P. Keränen, J. Maalampi, Phys. Lett. B 476, 205-212 (2000)], and (b) An earlier work - predating the work of Athar et al. - of J. G. Learned and S. Pakvasa [Astropart. Phys. 3, 267-274 (1995)]