NEUTRINO FACTORY AND BETA BEAM EXPERIMENTS AND DEVELOPMENT

The long-term prospects for fully exploring three-flavor mixing in the neutrino sector depend upon an ongoing and increased investment in the appropriate accelerator R and D. Two new concepts have been proposed that would revolutionize neutrino experiments, namely the Neutrino Factory and the Beta Beam facility. These new facilities would dramatically improve our ability to test the three-flavor mixing framework, measure CP violation in the lepton sector, and perhaps determine the neutrino mass hierarchy, and, if necessary, probe extremely small values of the mixing angle θ13. The stunning sensitivity that could be achieved with a Neutrino Factory is described, together with our present understanding of the corresponding sensitivity that might be achieved with a Beta Beam facility. In the Beta Beam case, additional study is required to better understand the optimum Beta Beam energy, and the achievable sensitivity. Neither a Neutrino Factory nor a Beta Beam facility could be built without significant R and D. An impressive Neutrino Factory R and D effort has been ongoing in the U.S. and elsewhere over the last few years and significant progress has been made towards optimizing the design, developing and testing the required accelerator components, and significantly reducing the cost. The recent progress is described here. There has been no corresponding activity in the U.S. on Beta Beam facility design and, given the very limited resources, there is little prospect of starting a significant U.S. Beta Beam R and D effort in the near future. However, the Beta Beam concept is interesting, and progress on its development in Europe should be followed. The Neutrino Factory R and D program has reached a critical stage in which support is required for two crucial international experiments and a third-generation international design study. If this support is forthcoming, a Neutrino Factory could be added to the Neutrino Community's road map in about a decade