Solar Neutrino Observations at the Sudbury Neutrino Observatory

Conference · Tue Apr 14 04:00:00 EDT 2020

OSTI ID:1670119

Poon, A. W. P. ^[1]

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1. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Inst. for Nuclear and Particle Astrophysics

The Sudbury Neutrino Observatory (SNO) is a 1000-tonne heavy water Cherenkov detector. Its usage of \dto as target allows the simultaneous measurements of the $$\nu_e$$ flux from $^8$B decay in the Sun and the total flux of all active neutrino species through the charged-current and the neutral-current interactions on the deuterons. Assuming the standard $$^{8}$$B shape, the $$\nu_e$$ component of the $$^{8}$$B solar neutrino flux is measured to be $$\phi_e = 1.76^{+0.05}_{-0.05}{(stat.)}^{+0.09}_{-0.09} {(syst.)} x 10^6 {\rm cm}^{-2} {\rm s}^{-1}$$ for a kinetic energy threshold of 5 MeV. The non-\nue component is found to be Φ_μτ $$\= 3.41^{+0.45}_{-0.45}{(stat.)}^{+0.48}_{-0.45} {(syst.)} x 10^6 {\rm cm}^{-2} {\rm s}^{-1}$$. This $$5.3\sigma$$ difference provides strong evidence for $$\nu_{e}$$ flavor transformation in the solar neutrino sector. The total active neutrino flux is measured with the neutral-current reaction at a neutrino energy threshold of 2.2 MeV. This flux is determined to be $$\phi_{NC} = 5.09^{+0.44}_{-0.43}{(stat.)}^{+0.46}_{-0.43} {(syst.)} x 10^6 {\rm cm}^{-2} {\rm s}^{-1}$$, and is consistent with solar model predictions. Assuming an undistorted $^8$B spectrum, the night minus day rate is 14.0$$\pm$$6.3(stat.)$$^{+1.5}_{-1.4}$$(sys.)\% of the average rate in the charged-current channel. If the total active neutrino flux is constrained to have no asymmetry, the night-day asymmetry in the $$\nu_e$$ flux is found to be 7.0$$\pm$$4.9(stat.)$$^{+1.3}_{1.2}$$(sys.)\%. A global analysis of all the available solar neutrino data in terms of matter-enhanced oscillations of two active flavors strongly favors the Large Mixing Angle (LMA) solution.

• Research Organization: Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Nuclear Physics (NP)
• Contributing Organization: Sudbury Neutrino Observatory Collaboration
• DOE Contract Number: AC02-05CH11231
• OSTI ID: 1670119
• Country of Publication: United States
• Language: English