0000000000886689
AUTHOR
J. Riittinen
Effects of degenerate sterile neutrinos on the supernova neutrino flux
We consider the possibility that there exist sterile neutrinos which are closely degenerate in mass with the active neutrinos and mixed with them. We investigate the effects of this kind of active-sterile neutrino mixing on the composition of supernova neutrino flux at the Earth. If an adiabatic MSW-transition between active and sterile neutrinos takes place, it could dramatically diminish the electron neutrino flux.
Sterile neutrino signals from supernovae
We investigate the effects of a mixing of active and sterile neutrinos on the ratios of supernova electron neutrino flux ($F_e$) and antineutrino flux ($F_{\bar e}$) to the total flux of the other neutrino and antineutrino flavours ($F_a$). We assume that the heaviest (in the normal hierarchy) Standard Model neutrino $\nu_3$ mixes with a sterile neutrino resulting in a pair of mass eigenstates with a small mass gap. Using the density matrix formalism we solve numerically the the evolution of neutrino states in the envelope of a supernova and determine the flux ratios $F_e/F_a$ and $F_{\bar{e}}/F_a$ as a function of the active-sterile mixing angle and for the experimentally allowed range of …
Landau-Zener problem in a three-level neutrino system with non-linear time dependence
We consider the level-crossing problem in a three-level system with non-linearly time-varying Hamiltonian (time-dependence $t^{-3}$). We study the validity of the so-called independent crossing approximation in the Landau-Zener model by making comparison with results obtained numerically in density matrix approach. We also demonstrate the failure of the so-called "nearest zero" approximation of the Landau-Zener level-crossing probability integral.
Effects of sterile neutrinos on the ultrahigh-energy cosmic neutrino flux
We investigate the effect of sterile neutrinos that are nearly degenerate with active ones on the flux of ultrahigh-energy cosmic ray neutrinos at earth. This offers a way to probe neutrino oscillations in the mass-squared range (10^{-16} eV^2 < ��m^2 < 10^{-11} eV^2) which maybe hard to detect by any other means. Taking into account the present experimental uncertainties of the active-active mixing angles and by allowing any values for the active-sterile mixing angles we find that the ratio of the electron and muon neutrino fluxes may change by -40 % to 70 % in comparison with the ratio in the absence of active-sterile mixing.