Supernova neutrinos can tell us the neutrino mass hierarchy independently of flux models

Department of Physics and Astronomy, University of Kansas, Lawrence, KS 66045, USA
Physics Letters B (Impact Factor: 6.02). 06/2005; DOI: 10.1016/j.physletb.2005.05.017
Source: arXiv

ABSTRACT We demonstrate that the detection of shock modulations of the neutrino spectra from a galactic core-collapse supernova is sufficient to obtain a high significance determination of the neutrino mass hierarchy if the supernova event is observed in both a Mton-class water Cherenkov detector and a 100 kton-class liquid argon detector. Neither detailed supernova neutrino flux modeling nor observation of Earth matter effects is needed for this determination. As a corollary, a nonzero value of θx will be established.

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    ABSTRACT: I discuss some aspects of future prospects of the experimental exploration of the unknowns in the neutrino mass pattern and the lepton flavor mixing. I start from measuring θ13 by reactors and accelerators as a prerequisite for proceeding to search for leptonic CP violation. I then discuss how CP violation can be uncovered, and how the neutrino mass hierarchy can be determined. I do these by resolving so called the "parameter degeneracy" which is required anyway if one wants to seek precision measurement of the lepton mixing parameters. As a concrete setting for resolving the degeneracy I use the Tokai-to-Kamioka-Korea two detector complex which receives neutrino superbeam from J-PARC, which is sometimes called as "T2KK". It is shown that T2KK is able to resolve all the eight-fold parameter degeneracy in a wide range of the lepton mixing parameters. Some alternative ways of measuring the unknowns are also briefly mentioned.
    International Journal of Modern Physics E 01/2012; 16(05). DOI:10.1142/S0218301307006691 · 0.84 Impact Factor
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    ABSTRACT: Matter effects modify the mixing and the effective masses of neutrinos in a way which depends on the neutrino mass hierarchy. Consequently, for normal and inverted hierarchies the oscillations and flavor conversion results are different. Sensitivity to the mass hierarchy appears whenever the matter effects on the 1-3 mixing and mass splitting become substantial. This happens in supernovae in wide energy range and in the matter of the Earth. The Earth density profile is a multi-layer medium where the resonance and parametric enhancements of oscillations occur. The enhancement is realized in neutrino (antineutrino) channels for the normal (inverted) mass hierarchy. Multi-megaton scale under ice (water) atmospheric neutrino detectors with low energy threshold can establish mass hierarchy with $(3 - 10) \sigma$ confidence level in few years. The main challenges of these experiments are discussed and various ways to improve sensitivity are outlined. In particular, inelasticity measurements will allow to increase significance of the hierarchy identification by $20 - 50 \%$ .


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