  We discuss the experimental requirements for a mass hierarchy measurement for
$\theta_{13}=0$ using muon neutrino disappearance. We find that a specially
optimized neutrino factory at $L \simeq 6 \,000 \, \mathrm{km}$ could do this
measurement using extreme luminosities. In particular, we do not require charge
identification for this purpose. In order to measure the mass hierarchy for
more adequate luminosities, we explore the capabilities of low energy narrow
band off-axis beams, which have relatively more events at low energies. We find
that, in this case, the energy resolution of the detector quickly becomes the
limiting factor of the measurement, and significantly affects the baseline
optimization for determining the mass hierarchy.
