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Title: Resolving the eightfold neutrino parameter degeneracy by two identical detectors with different baselines

Abstract

We have shown in a previous paper that two identical detectors with each fiducial mass of 0.27 megaton water, one in Kamioka and the other in Korea, which receive the (anti-) muon neutrino beam of 4 MW power from J-PARC facility have potential of determining the neutrino mass hierarchy and discovering CP violation by resolving the degeneracies associated with them. In this paper, we point out that the same setting has capability of resolving the {theta}{sub 23} octant degeneracy in region where sin{sup 2}2{theta}{sub 23} < or approx. 0.97 at 2 standard deviation confidence level even for very small values of {theta}{sub 13}. Altogether, it is demonstrated that one can solve all the eightfold neutrino parameter degeneracies in situ by using the Tokai-to-Kamioka-Korea setting if {theta}{sub 13} is within reach by the next generation superbeam experiments. We also prove the property called 'decoupling between the degeneracies', which is valid to first-order in perturbation theory of the earth matter effect, that guarantees approximate independence between analyses to solve any one of the three different type of degeneracies.

Authors:
;  [1];  [2];  [3]
  1. Research Center for Cosmic Neutrinos, Institute for Cosmic Ray Research, University of Tokyo, Kashiwa, Chiba 277-8582 (Japan)
  2. Department of Physics, Tokyo Metropolitan University, Hachioji, Tokyo 192-0397 (Japan)
  3. Departamento de Fisica, Pontificia Universidade Catolica do Rio de Janeiro, C. P. 38071, 22452-970, Rio de Janeiro (Brazil)
Publication Date:
OSTI Identifier:
20933209
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Review. D, Particles Fields; Journal Volume: 75; Journal Issue: 1; Other Information: DOI: 10.1103/PhysRevD.75.013006; (c) 2007 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; ANTINEUTRINO BEAMS; CP INVARIANCE; J-PARC; MASS; MUON NEUTRINOS; NEUTRINO BEAMS; PERTURBATION THEORY

Citation Formats

Kajita, Takaaki, Nakayama, Shoei, Minakata, Hisakazu, and Nunokawa, Hiroshi. Resolving the eightfold neutrino parameter degeneracy by two identical detectors with different baselines. United States: N. p., 2007. Web. doi:10.1103/PHYSREVD.75.013006.
Kajita, Takaaki, Nakayama, Shoei, Minakata, Hisakazu, & Nunokawa, Hiroshi. Resolving the eightfold neutrino parameter degeneracy by two identical detectors with different baselines. United States. doi:10.1103/PHYSREVD.75.013006.
Kajita, Takaaki, Nakayama, Shoei, Minakata, Hisakazu, and Nunokawa, Hiroshi. Mon . "Resolving the eightfold neutrino parameter degeneracy by two identical detectors with different baselines". United States. doi:10.1103/PHYSREVD.75.013006.
@article{osti_20933209,
title = {Resolving the eightfold neutrino parameter degeneracy by two identical detectors with different baselines},
author = {Kajita, Takaaki and Nakayama, Shoei and Minakata, Hisakazu and Nunokawa, Hiroshi},
abstractNote = {We have shown in a previous paper that two identical detectors with each fiducial mass of 0.27 megaton water, one in Kamioka and the other in Korea, which receive the (anti-) muon neutrino beam of 4 MW power from J-PARC facility have potential of determining the neutrino mass hierarchy and discovering CP violation by resolving the degeneracies associated with them. In this paper, we point out that the same setting has capability of resolving the {theta}{sub 23} octant degeneracy in region where sin{sup 2}2{theta}{sub 23} < or approx. 0.97 at 2 standard deviation confidence level even for very small values of {theta}{sub 13}. Altogether, it is demonstrated that one can solve all the eightfold neutrino parameter degeneracies in situ by using the Tokai-to-Kamioka-Korea setting if {theta}{sub 13} is within reach by the next generation superbeam experiments. We also prove the property called 'decoupling between the degeneracies', which is valid to first-order in perturbation theory of the earth matter effect, that guarantees approximate independence between analyses to solve any one of the three different type of degeneracies.},
doi = {10.1103/PHYSREVD.75.013006},
journal = {Physical Review. D, Particles Fields},
number = 1,
volume = 75,
place = {United States},
year = {Mon Jan 01 00:00:00 EST 2007},
month = {Mon Jan 01 00:00:00 EST 2007}
}
  • We explore the possibility of the simultaneous determination of neutrino mass hierarchy and the CP violating phase by using two identical detectors placed at different baseline distances. We focus on a possible experimental setup using a neutrino beam from the J-PARC facility in Japan with a beam power of 4 MW and megaton (Mton)-class water Cherenkov detectors, one placed in Kamioka and the other somewhere in Korea. We demonstrate, under reasonable assumptions of systematic uncertainties, that the two-detector complex with each fiducial volume of 0.27 Mton has a potential of resolving the neutrino mass hierarchy up to sin{sup 2}2{theta}{sub 13}>0.03more » (0.055) at 2{sigma} (3{sigma}) C.L. for any values of {delta} and at the same time has the sensitivity to CP violation by 4+4 years running of {nu}{sub e} and {nu}{sub e} appearance measurement. The significantly enhanced sensitivity is due to clean detection of the modulation of the neutrino energy spectrum, which is enabled by the cancellation of systematic uncertainties between two identical detectors which receive the neutrino beam with the same energy spectrum in the absence of oscillations.« less
  • The Kamioka-Korea two-detector system is a powerful experimental setup for resolving neutrino parameter degeneracies and probing CP violation in neutrino oscillation. In this paper, we study sensitivities of the same setup to several nonstandard neutrino physics such as quantum decoherence, tiny violation of Lorentz symmetry, and nonstandard interactions of neutrinos with matter. We show that it can achieve significant improvement on the current bounds on nonstandard neutrino physics. In most cases, the Kamioka-Korea two-detector setup is more sensitive than the one-detector setup, either in Kamioka or in Korea, except for the cases when Lorentz symmetry is broken in a CPT-violatingmore » manner and the nonstandard neutrino interactions with matter is present.« less
  • If the lepton mixing angle {theta}{sub 23} is not maximal, there arises a problem of ambiguity in determining {theta}{sub 23} due to the existence of two degenerate solutions, one in the first and the other in the second octant. We discuss an experimental strategy for resolving the {theta}{sub 23} octant degeneracy by combining reactor measurement of {theta}{sub 13} with accelerator {nu}{sub {mu}} disappearance and {nu}{sub e} appearance experiments. The robustness of the {theta}{sub 23} degeneracy and the difficulty in lifting it only by accelerator experiments with conventional {nu}{sub {mu}} (and {nu}{sub {mu}}) beams are demonstrated by analytical and numerical treatments.more » Our method offers a way to overcome the difficulty and can resolve the degeneracy between solutions sin{sup 2}{theta}{sub 23}=0.4 and sin{sup 2}{theta}{sub 23}=0.6 if sin{sup 2}2{theta}{sub 13} > or approx. 0.05 at 95% CL by assuming the T2K phase II experiment and a reactor measurement with an exposure of 10 GW{center_dot}kt{center_dot}yr. The dependence of the resolving power of the octant degeneracy on the systematic errors of reactor experiments is also examined.« less
  • We re-examine the possibility of reconstructing the initial fluxes of supernova neutrinos emitted in a future core-collapse galactic supernova explosion and detected in a megaton-sized water Cherenkov detector. A novel key element in our method is the inclusion, in addition to the total and the average energies of each neutrino species, of a 'pinching' parameter characterizing the width of the distribution as a fit parameter. We uncover in this case a continuous degeneracy in the reconstructed parameters of supernova neutrino fluxes at the neutrinosphere. We analyze in detail the features of this degeneracy and show how it occurs irrespective ofmore » the parameterization used for the distribution function. Given that this degeneracy is real we briefly comment on possible steps towards resolving it, which necessarily requires going beyond the setting presented here.« less
  • In this work we show that the physics reach of a long-baseline (LBL) neutrino oscillation experiment based on a superbeam and a megaton water Cherenkov detector can be significantly increased if the LBL data are combined with data from atmospheric neutrinos (ATM) provided by the same detector. ATM data are sensitive to the octant of {theta}{sub 23} and to the type of the neutrino mass hierarchy, mainly through three-flavor effects in e-like events. This allows to resolve the so-called {theta}{sub 23}- and sign({delta}m{sub 31}{sup 2})-parameter degeneracies in LBL data. As a consequence it becomes possible to distinguish the normal frommore » the inverted neutrino mass ordering at 2{sigma} C.L. from a combined LBL+ATM analysis if sin{sup 2}2{theta}{sub 13} > or approx. 0.02. The potential to identify the true values of sin{sup 2}2{theta}{sub 13} and the CP-phase {delta}{sub CP} is significantly increased through the lifting of the degeneracies. These claims are supported by a detailed simulation of the T2K (phase II) LBL experiment combined with a full three-flavor analysis of ATM data in the HyperKamiokande detector.« less