Solar neutrino spectrum, sterile neutrinos and additional radiation in the Universe

Dec, 2010
22 pages
Published in:
  • Phys.Rev.D 83 (2011) 113011
e-Print:

Citations per year

20112014201720202023051015
Abstract: (arXiv)
Recent results from the SNO, Super-Kamiokande and Borexino experiments do not show the expected upturn of the energy spectrum of events (the ratio RNobs/NSSMR \equiv N_{obs}/N_{SSM}) at low energies. At the same time, cosmological observations testify for possible existence of additional relativistic degrees of freedom in the early Universe: ΔNeff=12\Delta N_{eff} = 1 - 2. These facts strengthen the case of very light sterile neutrino, νs\nu_s, with Δm012(0.72)105\Delta m^2_{01} \sim (0.7 - 2) \cdot 10^{-5} eV2^2, which mixes weakly with the active neutrinos. The νs\nu_s mixing in the mass eigenstate ν1\nu_1 characterized by sin22α103\sin^2 2\alpha \sim 10^{-3} can explain an absence of the upturn. The mixing of νs\nu_s in the eigenstate ν3\nu_3 with sin2β0.1\sin^2 \beta \sim 0.1 leads to production of νs\nu_s via oscillations in the Universe and to additional contribution ΔNeff0.71\Delta N_{eff} \approx 0.7 - 1 before the big bang nucleosynthesis and later. Such a mixing can be tested in forthcoming experiments with the atmospheric neutrinos as well as in future accelerator long baseline experiments. It has substantial impact on conversion of the supernova neutrinos.
Note:
  • 27 pages, LaTeX, 14 eps figures, 3 figures and additional considerations added
  • 14.60.Pq
  • neutrino: sterile
  • neutrino: atmosphere
  • neutrino: supernova
  • neutrino: spectrum
  • neutrino: solar
  • nucleosynthesis: big bang
  • accelerator
  • KAMIOKANDE
  • Borexino