Optimizing the greenfield Beta-beam

A comprehensive and detailed comparison of the physics reach of Beta-beam experiments between two pairs of plausible source ions, (8B, 8Li) and (18Ne, 6He) is performed. We study the optimal choices for the baseline, boost factor, and luminosity. We take a 50 kton iron calorimeter, a la ICAL-INO, as the far detector. We follow two complementary approaches for our study: (i) Fixing the number of useful ion decays and boost factor of the beam, and optimizing for the sensitivity reach between the two pairs of ions as a function of the baseline, (ii) Matching the shape of the spectrum between the two pairs of ions, and studying the requirements for baseline, boost factor, and luminosity. We find that for each pair of ions there are two baselines with very good sensitivity reaches: a short baseline with L [km]/γ ≅ 2.6 (8B+8Li) and L [km]/γ ≅ 0.8 (18Ne+6He), respectively, and a long 'magic' baseline. For γ ∼ 500, one would optimally use 6He and 18Ne at the short baseline for CP violation, 8B and 8Li at the magic baseline for the mass hierarchy, and either 6He and 18Ne at the short baseline or 8B and 8Li at the magic baseline for the sin2 2θ13 discovery.