Neutrino oscillation physics with a higher γ β - beam

The precision measurement and discovery potential of a neutrino factory based on boosted radioactive ions in a storage ring (" β-beam ") is reexamined. In contrast with past designs, which assume ion γ factors of ∼ 100 and baselines of L = 130 km, we emphasize the advantages of boosting the ions to higher γ and increasing the baseline proportionally. In particular, we consider a " medium-" γ scenario (γ ∼ 500, L ∼ 730 km) and a " high-" γ scenario (γ ∼ 2000, L ∼ 3000 km). The increase in statistics, which grow linearly with the average beam energy, the ability to exploit the energy dependence of the signal and the sizable matter effects at this longer baseline all increase the discovery potential of such a machine very significantly.