



The Sudbury Neutrino Observatory has been constructed to study the fundamental properties of neutrinos, in particular the mass and mixing parameters. Neutrino oscillations between the electron-flavour neutrino and another neutrino flavour have been proposed as an explanation of the observed shortfall in the flux of solar neutrinos reaching the Earth, as compared with theoretical expectations. SNO has proven this hypothesis by measuring the flux of electron type neutrinos which are produced in the Sun via the charged current interaction (CC), and comparing it to the flux of all active flavours of solar neutrinos detected on Earth in an appropriate energy interval via the neutral current (NC) and elastic scattering (ES) reactions. SNO can also test the oscillation hypothesis in the atmospheric neutrino sector by measuring an angular distribution of arrival directions from muon type neutrinos. Observation of neutrino flavor transformation is compelling evidence of neutrino mass. Non-zero neutrino mass is evidence for physics beyond the Standard Model of fundamental particle interactions.

Having resolved the long-standing solar neutrino problem by showing that solar neutrinos do change flavour, SNO's mission is now to study the oscillation mechanism itself in detail and to search for any further surprises that neutrinos may have in store for us.









