Low energy solar neutrino analysis of the salt phase of the Sudbury neutrino observatory

Thumbnail Image
Kos, Mark Szymon
Neutrinos , Particle astrophysics
The neutrino fluxes from the neutral current (NC), charged current (CC), and elastic scattering (ES) neutrino interactions in the salt phase of SNO have been extracted. The signals were extracted above an energy threshold of 4MeV, which is the lowest energy threshold at which the neutrino signals have been extracted from SNO to date. To achieve this low energy threshold the internal and external radioactive background signals have also been measured. The $^{8}$B neutrino fluxes for the 4MeV threshold were found to be \begin{eqnarray*} \Phi_{CC} & = & 1.60 ~^{+0.04}_{-0.04}~(\mbox{stat}) ~^{+0.06}_{-0.06}~(\mbox{syst}) \times 10^6 \mbox{cm}^{-2} \mbox{sec}^{-1},\\ \Phi_{NC} & = & 4.84 ~^{+0.16}_{-0.16}~(\mbox{stat}) ~^{+0.29}_{-0.32}~(\mbox{syst}) \times 10^6 \mbox{cm}^{-2} \mbox{sec}^{-1},\\ \Phi_{ES} & = & 2.75 ~^{+0.23}_{-0.23}~(\mbox{stat}) ~^{+0.25}_{-0.26}~(\mbox{syst}) \times 10^6 \mbox{cm}^{-2} \mbox{sec}^{-1}. \end{eqnarray*} \noindent These results are in agreement with the values published in ~\cite{SNO3} and the NC flux is in agreement with the standard solar model calculation from ~\cite{bp2004}. The published fluxes were \begin{eqnarray*} \Phi_{CC} &= & 1.68 ~^{+0.06}_{-0.06}~(\mbox{stat}) ~^{+0.08}_{-0.09}~(\mbox{syst}) \times 10^6 \mbox{cm}^{-2} \mbox{sec}^{-1} , \\ \Phi_{NC} &= & 4.94 ~^{+0.21}_{-0.21}~(\mbox{stat}) ~^{+0.38}_{-0.34}~(\mbox{syst}) \times 10^6 \mbox{cm}^{-2} \mbox{sec}^{-1}, \\ \Phi_{ES} &= & 2.35 ~^{+0.22}_{-0.22}~(\mbox{stat}) ~^{+0.15}_{-0.15}~(\mbox{syst}) \times 10^6 \mbox{cm}^{-2} \mbox{sec}^{-1}. \end{eqnarray*} \noindent The uncertainties on the extracted NC and CC fluxes are significantly smaller than on the published values. A comparison of the total uncertainty from flux measurements presented here and those published are given below. \begin{table}[htp] \begin{center} \begin{tabular}{|c|c|c|} \hline & uncertainties presented here (\%) & uncertainties from ~\cite{SNO3} (\%) \\ \hline $\Phi_{CC}$ & $~^{+4.6}_{-4.4}$ & $~^{+5.9}_{-6.4}$ \\ \hline $\Phi_{NC}$ & $~^{+6.8}_{-7.4}$ & $~^{+8.9}_{-8.2}$ \\ \hline $\Phi_{ES}$ & $~^{+12.3}_{-12.6}$ & $~^{+11.3}_{-11.3}$ \\ \hline \end{tabular} \label{funcert1} \end{center} \end{table} The shape of the CC energy spectrum has also been extracted with the 4MeV energy threshold. The uncertainties on the extracted fluxes are smaller than what was previously published. The CC spectrum gives a measure of the neutrino energy shape distortion due to neutrino oscillations. The uncertainties on the lowest energy bins in the extracted CC spectrum are much larger than the predicted distortion. We are therefore not sensitive to the upturn in the neutrino survival probability at lower energies predicted by neutrino oscillations in the large mixing angle (LMA) region.
External DOI