Optimization of the Two-Baseline Beta Beam

We propose a β-Beam experiment with four source ions and two baselines for the best possible sensitivity to θ13, CP violation and mass hierarchy. Neutrinos from 18Ne and 6He with Lorentz boost γ 350 are detected in a 500 kton water Cerenkov detector at a distance L = 650 km from the source. Neutrinos from 8B and 8Li are detected in a 50 kton magnetized iron detector at a distance L = 7000 km from the source. Since a tilt angle θ = 34.5 deg. is required to send the beam to the magic baseline, the far end of the ring has a maximum depth of d = 2132 m. We alleviate this problem by proposing to trade reduction of the decay ring with the increase in the boost factor of the 8Li and 8B ions up to γ8Li = 390 and γ8Li = 650, such that the number of events at the detector remains almost the same. We study the sensitivity reach of this two-baseline two-storage ring β-Beam experiment, and compare it with the corresponding reach of the other proposed facilities.