Astronomy and Astrophysics – Astrophysics
Scientific paper
Jan 1993
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1993phdt........43k&link_type=abstract
PhD Dissertation, Ohio State Univ. Columbus, OH United States
Astronomy and Astrophysics
Astrophysics
13
Helium Isotopes, Nuclear Fusion, Solar Neutrinos, Standard Model (Particle Physics), Astronomical Models, Big Bang Cosmology, Oscillations, Abundance, Universe, Astrophysics, Particle Mass, Annual Variations
Scientific paper
Two astrophysical environments are used to constrain possible extensions of the standard model of particle physics. The first environment considered is the sun, the second is the big bang. With the sun as a neutrino source, neutrino masses as small as 10-6 eV, and mixing angles as small as thetanu approximately equal to 10-4, can be probed. We use the measured solar neutrino fluxes of the Davis experiment, Kamiokande, Gallex and Sage and the predictions of standard solar models to investigate neutrino oscillation solutions to the solar neutrino problem, and thus constrain neutrino mass matrix elements. We consider flavor and sterile 'just-so' and Mikheyev-Smirnov-Wolfenstein (MSW) neutrino oscillation solutions to the solar neutrino problem. We show which commonly used approximations, such as the treatment of the cross-section and trigger in Kamiokande, and the level crossing formulae for the MSW effect, are valid in the context of calculating numerically the neutrino oscillation solutions. We demonstrate that the Kamiokande experiment was not sensitive to the semi-annual variations predicted by just-so oscillation theory, and that the proposed Borexino experiment has a promising chance to see the semi-annual variations. The solutions for the just-so and MSW scenarios are shown to be largely constrained by the Davis experiment. Without Davis' results it is not possible to significantly constrain the mass parameter Delta m2. For sterile MSW we predict the event rate in the planned Sudbury Neutrino Observatory neutral current experiment. The big bang nucleosynthesis (BBN) prediction for He-4 is sensitive to additional contributions to the energy density of the universe when the temperature is order 1 MeV. Using observational upper bounds on D + He-3 and He-4 the number of additional light degrees of freedom can be constrained. The following factors are considered in determining the 3rd significant figure for the predicted He-4 abundance: improved numerical integration of the nuclear abundances, order alpha (coulomb, radiative, and finite temperature) and MN-1 corrections to the weak rates. The combination of these effects result in a increase of the predicted BBN abundance of Yp of .0031, and including the latest uncertainty in the neutron life-time, a concomitant decrease of .27 for the number of additional light neutrinos permitted by standard BBN.
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