Determining Neutrino Mass Hierarchy by Precision Measurements in Electron and Muon Neutrino Disappearance Experiments

Recently a new method for determining the neutrino mass hierarchy by comparing the effective values of the atmospheric ∆m measured in the electron neutrino disappearance channel, ∆m(ee), with the one measured in the muon neutrino disappearance channel, ∆m(μμ), was proposed. If ∆m(ee) is larger (smaller) than ∆m(μμ) the hierarchy is of the normal (inverted) type. We re-examine this proposition in the light of two very high precision measurements: ∆m(μμ) that may be accomplished by the phase II of the Tokai-to-Kamioka (T2K) experiment, for example, and ∆m(ee) that can be envisaged using the novel Mössbauer enhanced resonant ν̄e absorption technique. Under optimistic assumptions for the systematic uncertainties of both measurements, we estimate the parameter region of (θ13, δ) in which the mass hierarchy can be determined. If θ13 is relatively large, sin 2 2θ13 >∼ 0.05, and both of ∆m (ee) and ∆m(μμ) can be measured with the precision of ∼ 0.5 % it is possible to determine the neutrino mass hierarchy at > 95% CL for 0.3π <∼ δ <∼ 1.7π for the current best fit values of all the other oscillation parameters.