Neutrino Physics

Our knowledge of the neutrino sector of the Standard Model has recently undergone a revolution. Deficits of the atmospheric muon neutrino flux and the solar electron neutrino flux compared with their predicted values can be understood in terms of neutrino oscillations, and we can therefore infer that neutrinos have non-degenerate masses. Additional but somewhat less secure evidence for electron to muon neutrino oscillations has been found in an accelerator experiment. Because these atmospheric, solar, and accelerator experiments have widely different baseline-to-energy ranges, the neutrino mass-squared differences required to explain the phenomena must be distinct. Given the recent observations, an important next step is to deduce the pattern of neutrino masses and mixings.

We are currently considering the physics capabilities of short- and long-baseline experiments at a neutrino factory in three- and four-neutrino scenarios that can explain the results of the current experiments. We will next address oscillation measurements that can be made in large water Cherenkov detectors and in the IceCube detector with both neutrino factories and upgraded conventional beam sources.

The future phenomenology of neutrino oscillations promises to be rich and varied, and we have a number of other interesting studies underway. We are considering the neutrino mixing matrix of specific theoretical models to see how the models can be tested experimentally. We are also preparing to analyze the solar neutrino data from the Sudbury Neutrino Observatory experiment as it becomes available.