#### Date of Award

1999

#### Document Type

Dissertation

#### Degree Name

Doctor of Philosophy (PhD)

#### First Advisor

Robert C. Svoboda

#### Abstract

The spectrum of recoil electrons from solar neutrino scattering above 6.5 MeV has been measured using the first 504 days of Super-Kamiokande detector data. The scattering rate is found to be 13.56 +/- 0.42(stat. ) +/- 0.29(syst.) events/day/22.5kton, which is a factor of 0.474 +/- 0.015(stat.) +/- 0.010( syst.) of the expected rate. The measured spectrum and the expected spectra from 8B and HeP Neutrino scattering are compared using a chi2 minimization process to find the best-fit match between the measured neutrino rates and a linear combination of the expected rates from 8B and HeP neutrinos. Using only the 8B expected spectrum the fitting procedure results in a best-fit scaling factor of 0.479; that is, the 8B expected spectrum best matches the measured spectrum if it is scaled by 0.479. This best-fit has a chi 2 value of 19.05 with 15 degrees of freedom, which corresponds to a confidence level of 21.2%. The ratio of the measured spectrum to the scaled 8B expected spectrum results in an upturn at higher energies which may be an artifact of statistics or an indication of neutrino oscillations or of some other phenomenon. Using both the 8B and HeP expected spectra in the fitting procedure results in a 8B best-fit scaling factor of 0.446 and a HeP best-fit scaling factor of 25.1. This best-fit has a chi2 value of 12.85 with 14 degrees of freedom, which corresponds to a confidence level of 53.8%. The larger-than-standard HeP neutrino contribution flattens the upturn at higher energies and, thus, results in a lower chi 2 value. This dissertation describes in detail the analysis that produced these results.

#### Recommended Citation

Sanford, Robert Ellis Jr, "Spectrum of Solar Neutrinos Above 6.5 MeV." (1999). *LSU Historical Dissertations and Theses*. 6959.

https://repository.lsu.edu/gradschool_disstheses/6959

#### ISBN

9780599372689

#### Pages

198

#### DOI

10.31390/gradschool_disstheses.6959