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Determination of the neutrino mass hierarchy via the phase of the disappearance oscillation probability with a monochromatic ῡe source

Abstract:

The neutrino mass hierarchy can be determined, in principle, by measuring a phase in the disappearance oscillation probability in vacuum, without relying on the matter effect, using a single channel. This phase is not the same for the normal and inverted neutrino mass spectra. In this paper, we give a complete description and physics understanding of the method. The key feature of the method is to detect advancement (normal) or retardation (inverted) of the phase of the atmospheric-scale oscillation relative to the solar-scale oscillation. We then show that this method can be realized with the recently proposed resonant ν̄e absorption reaction enhanced by the Mössbauer effect. The unique feature of this setup is the ultramonochromaticity of the observed ν̄e's. Because of this feature, the phase advancement or retardation of atmospheric-scale neutrino oscillation is detectable after 20 or more oscillations if the source and the target are made sufficiently compact in size. A quantitative estimate of the sensitivity to mass hierarchy resolution is given. We have also examined how a possible continuation of such an experiment can be carried out in order also to achieve high precision (few percent) determination of the solar-scale oscillation parameters Δm212 and θ12. © 2007 The American Physical Society.