Independent Measurement of the Total Active 8B Solar Neutrino Flux Using an Array of 3He Proportional Counters at the Sudbury Neutrino Observatory

TL;DR

The Sudbury Neutrino Observatory used an array of 3He proportional counters to measure the rate of neutral-current interactions in heavy water and precisely determined the total active (nu_x) 8B solar neutrino flux, in agreement with previous measurements and standard solar models.

Abstract

The Sudbury Neutrino Observatory (SNO) used an array of 3He proportional counters to measure the rate of neutral-current interactions in heavy water and precisely determined the total active (nu_x) 8B solar neutrino flux. This technique is independent of previous methods employed by SNO. The total flux is found to be 5.54(+0.33/-0.31 stat, +0.36/-0.34 syst) x 10^6 cm^-2 s^-1, in agreement with previous measurements and standard solar models. A global analysis of solar and reactor neutrino results yields Delta m^2 = 7.59(+0.19/-0.21) x 10^-5 eV^2 and theta = 34.4(+1.3/-1.2) degrees. The uncertainty on the mixing angle has been reduced from SNO's previous results.

Figures (2)

• Figure 1: NCD energy spectrum fit with a neutron calibration spectrum, neutron backgrounds, alpha background derived from Monte Carlo simulation, and low-energy instrumental background distributions. Data are shown after data reduction up to 1.4 MeV, and the fit is above 0.4 MeV.
• Figure 2: Neutrino-oscillation contours. (a) SNO only: D$_2$O & salt day and night spectra, NCD phase fluxes. The best-fit point is $\Delta m^2=4.57\times10^{-5}$ eV$^2$, $\tan^{2}\theta=0.447$, $f_{B}=0.900$, with $\chi^{2}$/d.o.f.=73.77/72. (b) Solar Global: SNO, SK, Cl, Ga, Borexino. The best-fit point is $\Delta m^2=4.90\times10^{-5}$ eV$^2$, $\tan^{2}\theta=0.437$, $f_{B}=0.916$. (c) Solar Global + KamLAND. The best-fit point is $\Delta m^2=7.59\times10^{-5}$ eV$^2$, $\tan^{2}\theta=0.468$, $f_{B} = 0.864$.