Neutrino Factories and the "Magic" Baseline

Abstract

We show that for a neutrino factory baseline of $L\sim 7300km-7600km$ a ``clean'' measurement of ${\sin }^{2}2{\theta }_{13}$ becomes possible, which is almost unaffected by parameter degeneracies. We call this baseline "magic" baseline, because its length only depends on the matter density profile. For a complete analysis, we demonstrate that the combination of the magic baseline with a baseline of 3000 km is the ideal solution to perform equally well for the ${\sin }^{2}2{\theta }_{13}$, sign of $\Delta m_{31}^2$, and CP violation sensitivities. Especially, this combination can very successfully resolve parameter degeneracies even below ${\sin }^{2}2{\theta }_{13}<10^{-4}$.

Comments: Minor changes, final version to appear in PRD, 4 pages, 3 figures, RevTeX