Sudbury Neutrino Observatory Results

TL;DR

The Sudbury Neutrino Observatory's measurements confirmed neutrino flavor change, resolving the Solar Neutrino Problem and providing strong evidence for neutrino oscillations beyond the Standard Model.

Contribution

First direct measurement showing neutrino flavor change using heavy water Cherenkov detector, confirming neutrino oscillations and resolving the Solar Neutrino Problem.

Findings

Electron neutrinos change to other active neutrino types.

Total active neutrino flux matches solar model predictions.

Neutrino oscillation parameters are well constrained.

Abstract

The Sudbury Neutrino Observatory uses 1000 tonnes of heavy water in an ultra-clean Cherenkov detector situated 2 km underground in Ontario, Canada to study neutrinos from the Sun and other astrophysical sources. The Charged Current (CC) reaction on deuterium is sensitive only to electron neutrinos whereas the Neutral Current (NC) is equally sensitive to all active neutrino types. By measuring the flux of neutrinos from 8B decay in the Sun with the CC and NC reactions it has been possible to establish clearly, through an appearance measurement, that electron neutrinos change to other active neutrino types, properties that are beyond the Standard Model of elementary particles. The observed total flux of active neutrinos agrees well with solar model flux calculations for 8B. This provides a clear answer to the "Solar Neutrino Problem". When these results are combined with other measurements, the oscillation of massive neutrinos is strongly defined as the primary mechanism for flavor change and oscillation parameters are well constrained.