Session J12: Solar and Reactor Neutrinos

$^{8}$B Solar Neutrino Flux and Spectrum Results from the SNO Salt Phase

Sudbury Neutrino Observatory measurements of the flux of $^{8}$B solar neutrinos from the full salt dataset will be presented with particular focus on the charged current (CC) energy spectrum and neutral current (NC) flux results. A description of detector calibration and systematic uncertainty evaluations for the salt phase will be given including energy, reconstruction, and background evaluations. Comparisons with previous SNO results and measurements from other experiments will be provided in order to illustrate the impact of these latest results and to summarize the current state of the field.   

The Day-Night Effect and MSW Analysis for the Salt Phase of SNO

The Sudbury Neutrino Observatory (SNO) has recently extended its analysis of data from the dissolved-salt phase of the experiment to the full 391-day salt data set. In addition to measurements of the total $^8$B solar neutrino flux, solar neutrino flavor change, and the solar electron neutrino energy spectrum, the recent analysis includes day and night measurements of the electron and total solar neutrino fluxes. A day-night asymmetry in the electron neutrino flux is a prediction of the MSW model for solar neutrino oscillations for some values of the fundamental neutrino parameters, due to the matter effects in the earth. The day-night analysis for the salt phase of SNO will be presented, as well as a discussion of the implications of SNO's salt phase measurements in a global analysis to determine solar neutrino parameters $\Delta{m}^2$ and $\sin^2{\theta}$.   

The Neutral Current Detector Phase of the Sudbury Neutrino Observatory

The Sudbury Neutrino Observatory (SNO) has recently started taking data in the Neutral Current Detector (NCD) phase, in which an array of forty $^3$He- and $^4$He-filled proportional counter strings has been added to SNO's heavy water to detect neutrons liberated in neutral current interactions of neutrinos with deuterium. Pulse shape analysis of digitized current pulses from the NCDs is used to achieve the background rejection necessary to extract the neutral current signal. Alphas from uranium and thorium contamination in the NCD bodies are the primary physics background to the NCD neutron signal. This talk will focus on the NCD analysis techniques under development, and, in particular, emphasize techniques for discrimination against alpha backgrounds.   

Search for the $\rm ^{8}{B}(2^+) \rightarrow {^8}Be(0^+)$ transition

The beta decay of $\rm^{8}{B}$ is an important reaction for both solar neutrino physics and understanding the nuclear physics in the mass-8 system. We are searching for the second-forbidden $\rm ^{8}{B}(2^+) \rightarrow {^8}{Be}(0^+, g.s.)$ transition, which has never before been experimentally detected. The observable signature for this transition is the 92-keV $2\alpha$ decay of the ground state of $\rm{^8}{Be}$. This talk will discuss the development of an $\rm^8 B$ radioactive beam at the UW Tandem and our novel technique for measuring the low-energy signature of this transition. A branching-ratio limit will be given, as well as a comparison of this limit to theoretical estimates.   

Limit On The Neutrino Magnetic Moment Using Super-Kamiokande Solar Neutrino Data

Nonzero neutrino magnetic moment would mean new physics beyond the standard model. Therefore a search for nonzero neutrino magnetic moment has been conducted using the high statistic 1496 live day solar neutrino data from Super-Kamiokande-I. Specifically, this search looked for distortions to the $^{8}$B solar neutrino energy spectrum. A nonzero neutrino magnetic moment would cause an increase of event rates at lower energies. The search found no clear signal of neutrino magnetic moment. A limit of $\mu_{\nu} \leq 3.6 \times 10^{-10}$ $\mu_{B}$ at 90\% C.L. on the neutrino magnetic moment has been obtained by fitting to the Super-K day/night energy spectra. The fitting took into account the effects of neutrino oscillation on the shape of energy spectra. With the results from other neutrino experiments constraining the oscillation region, a limit of $\mu_{\nu} \leq 1.1 \times 10^{-10}$ $\mu_{B}$ at 90\% C.L was obtained.   

Uncertainties in the Anti-neutrino Production from Nuclear Reactors

Anti-neutrino emission rates and energy spectra from nuclear reactors are determined by the thermal power and fuel composition. The uncertainties in these quantities contribute to the systematic error in reactor anti-neutrino experiments. Impact of the uncertainties on the calculated interaction rates in anti-neutrino detectors is examined. Various correlations between the leading uncertainties are discussed.