Big Bang Nucleosynthesis and Cosmological Constraints on Neutrino Oscillation Parameters
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We present a review of cosmological nucleosynthesis (CN) with neutrino oscillations, discussing the different effects of oscillations on CN, namely: increase of the effective degrees of freedom during CN, spectrum distortion of the oscillating neutrinos, neutrino number density depletion, and growth of neutrino-antineutrino asymmetry due to active-sterile oscillations. We discuss the importance of these effects for the primordial yield of helium-4.
Primordially produced He-4 value is obtained in a selfconsistent study of the nucleons and the oscillating neutrinos. The effects of spectrum distortion, depletion and neutrino-antineutrino asymmetry growth on helium-4 production are explicitly calculated.
An update of the cosmological constraints on active-sterile neutrino oscillations parameters is presented, giving the values: delta m^2 sin^8 (2 theta) < 1.5 x 10^{-9} eV^2 for delta m^2 > 0, and |delta m^2| < 8.2 x 10^{-10} eV^2 at large mixing angles for delta m^2 < 0. According to these constraints, besides the active-sterile LMA solution, also the active-sterile LOW solution to the solar neutrino problem is almost totally excluded.
Extended and updated version of the invited talk, presented at the International Conference "Hot Points in Astrophysics", held in JINR, Dubna, Russia, August 22-26, 2000. An update of the cosmological constraints on active-sterile neutrino oscillation parameters is presented (Fig.2 added)
Extended and updated version of the invited talk, presented at the International Conference "Hot Points in Astrophysics", held in JINR, Dubna, Russia, August 22-26, 2000. An update of the cosmological constraints on active-sterile neutrino oscillation parameters is presented (Fig.2 added)