Article

# 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
(Impact Factor: 6.13). 06/2005; 617(3-4):167-173. 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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• "In particular, a lot of attention has been devoted to possible signatures of the Mikheyev-Smirnov-Wolfenstein (MSW) matter effect [1] on neutrino flavor evolution [2] [3] [4]. Shock-wave effects in the stellar envelope [6] [7] [8] [9] [10] [11] [12] [13] [14] [15] [16] [17] [18] and the neutrino Earth matter crossing [19] [20] [21] [22] [23] [24] [25] have been predicted to have dramatic effects on SN neutrino oscillations and to produce signatures that could allow us to extract valuable information on the unknown neutrino mass and mixing parameters, like the neutrino mass hierarchy and the mixing angle θ 13 . "
##### Article: Signatures of collective and matter effects on supernova neutrinos at large detectors
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ABSTRACT: We calculate the expected galactic supernova neutrino signal at large next-generation underground detectors. At different epochs after the explosion, the primary fluxes can be quite different. For these primary neutrino fluxes, spectral splits induced by collective neutrino flavor transformations can arise for either mass hierarchy in both neutrino and antineutrino channels. We classify flux models according to the nature and number of these splits, and calculate the observable electron-neutrino and electron-antineutrino spectra at Earth, taking into account subsequent matter effects. We find that some of the spectral splits could occur sufficiently close to the peak energies to produce significant distortions in the observable SN neutrino signal. The most striking signature of this effect would be presence of peculiar energy dependent modulations associated with Earth matter crossing, present only in portions of the SN neutrino energy spectra demarcated by spectral splits. These signatures at proposed large water Cherenkov, scintillation, and liquid Argon detectors could give hints about the primary SN neutrino fluxes, as well as on the neutrino mass hierarchy and the mixing angle theta_{13}. Comment: 18 Pages, 5 figures and 4 tables
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• "This scenario of resonant neutrino conversions in a SN [5] has been studied extensively to probe neutrino mixings and SN dynamics. The work has focussed on the determination of mass hierarchy and signatures of a non-zero θ 13 [6] [7], earth matter effects on the neutrino fluxes when they pass through matter [8] [9] [10], shock wave effects on observable neutrino spectra and their model independent signatures [11] [12] [13] [14] [15] [16]. Recently, possible interference effects for multiple resonances [17], the role of turbulence in washing out shock wave effects [18] [19] [20], and time variation of the signal [21] have also been explored. "
##### Article: Collective three-flavor oscillations of supernova neutrinos
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ABSTRACT: Neutrinos and antineutrinos emitted from a core collapse supernova interact among themselves, giving rise to collective flavor conversion effects that are significant near the neutrinosphere. We develop a formalism to analyze these collective effects in the complete three-flavor framework. It naturally generalizes the spin-precession analogy to three flavors and is capable of analytically describing phenomena like vacuum/MSW oscillations, synchronized oscillations, bipolar oscillations and spectral split. Using the formalism, we demonstrate that the flavor conversions may be "factorized" into two-flavor oscillations with hierarchical frequencies. We explicitly show how the three-flavor solution may be constructed by combining two-flavor solutions. For a typical supernova density profile, we identify an approximate separation of regions where distinctly different flavor conversion mechanisms operate, and demonstrate the interplay between collective and MSW effects. We pictorialize our results in terms of the "e_3 - e_8 triangle" diagram, which is a tool that can be used to visualize three-neutrino flavor conversions in general, and offers insights into the analysis of the collective effects in particular. Comment: 44 pages, 24 figures. Typo corrected in Eqs. (52, 68, 85 and 91) of the version published in PRD. Results unchanged
Physical review D: Particles and fields 12/2007; 77(11). DOI:10.1103/PhysRevD.77.113002 · 4.86 Impact Factor
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• "In particular, the effects of supernova shock waves on neutrino flavor transitions in matter [5] are gaining increasing attention in the recent literature [6] [7] [8] [9] [10] [11]. Indeed, for a few seconds after the SN core bounce, the strong time dependence of the shock-wave profile can leave peculiar signatures on the time structure of the neutrino events, which could be monitored in large, real-time detectors [12] [13] [14]. "
##### Article: Damping of supernova neutrino transitions in stochastic shock-wave density profiles
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ABSTRACT: Supernova neutrino flavor transitions during the shock wave propagation are known to encode relevant information not only about the matter density profile but also about unknown neutrino properties, such as the mass hierarchy (normal or inverted) and the mixing angle theta_13. While previous studies have focussed on "deterministic" density profiles, we investigate the effect of possible stochastic matter density fluctuations in the wake of supernova shock waves. In particular, we study the impact of small-scale fluctuations on the electron (anti)neutrino survival probability, and on the observable spectra of inverse-beta-decay events in future water-Cherenkov detectors. We find that such fluctuations, even with relatively small amplitudes, can have significant damping effects on the flavor transition pattern, and can partly erase the shock-wave imprint on the observable time spectra, especially for sin^2(theta_13) > O(10^-3). Comment: v2 (23 pages, including 6 eps figures). Typos removed, references updated, matches the published version
Journal of Cosmology and Astroparticle Physics 03/2006; 0606(6). DOI:10.1088/1475-7516/2006/06/012 · 5.81 Impact Factor