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

Department of Physics, University of Wisconsin, Madison, WI 53706, USA; Department of Physics and Astronomy, University of Kansas, Lawrence, KS 66045, USA
Physics Letters B (Impact Factor: 4.57). 01/2005; 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: Neutrinos of astrophysical origin are messengers produced in stars, in explosive phenomena like core-collapse supernovae, in the accretion disks around black holes, or in the Earth's atmosphere. Their fluxes and spectra encode information on the environments that produce them. Such fluxes are modified in characteristic ways when neutrinos traverse a medium. Here our current understanding of neutrino flavour conversion in media is summarized. The importance of this domain for astrophysical observations is emphasized. Examples are given of the fundamental properties that astrophysical neutrinos have uncovered, or might reveal in the future.
    Annalen der Physik 03/2013; · 1.51 Impact Factor
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    ABSTRACT: We study the sensitivity of future medium baseline reactor antineutrino experiments on the neutrino mass hierarchy. By using the standard chi^2 analysis, we find that the sensitivity depends strongly on the baseline length L and the energy resolution (delta E/E)^2 = (a/sqrt{E/MeV})^2 + b^2, where a and b parameterize the statistical and systematic uncertainties, respectively. The optimal length is found to be L ~ 40-55 km, where a slightly shorter L in the range is preferred for poorer energy resolution. The running time needed to determine the mass hierarchy also depends strongly on the energy resolution; for a 5 kton detector (with 12% weight fraction of free proton) placed at L ~ 50 km away from a 20 GW_{th} reactor, three-sigma determination needs 14 years of running with a = 3% and b = 0.5%, which can be reduced to 5 years if a = 2% and b = 0.5%. On the other hand, the experiment can measure the mixing parameters accurately, achieving delta sin^2(2theta_{12}) ~ 4*10^{-3}, delta (m_2^2-m_1^2) ~ 0.03*10^{-5} eV^2, and delta |m_3^2 -m_1^2| ~ 0.007*10^{-3} eV^2, in 5 years, almost independently of the energy resolution for a < 3% and b < 1%. In order to compare our simple (Delta chi^2)_{min} results with those obtained by simulating many experiments, we develop an efficient method to estimate the uncertainty of (Delta chi^2)_{min}, and the probability for determining the right mass hierarchy by an experiment is presented as a function of the mean (Delta chi^2)_{min}.
    Journal of High Energy Physics 10/2012; 2013(5). · 5.62 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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