Article

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

• ##### H. Nunokawa
Physical review D: Particles and fields 01/2007; 75(1). DOI: 10.1103/PhysRevD.75.013006
Source: arXiv

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 θ23 octant degeneracy in region where sin⁡22θ23≲0.97 at 2 standard deviation confidence level even for very small values of θ13. 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 θ13 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.

0 Bookmarks
·
47 Views
• ##### Article: Resolving the octant of θ 23 with T2K and NOνA
[Hide abstract]
ABSTRACT: Preliminary results of MINOS experiment indicate that θ 23 is not maximal. Global fits to world neutrino data suggest two nearly degenerate solutions for θ 23: one in the lower octant (LO: θ 23 < 45◦) and the other in the higher octant (HO: θ 23 > 45◦). ν μ → ν e oscillations in superbeam experiments are sensitive to the octant and are capable of resolving this degeneracy. We study the prospects of this resolution by the current T2K and upcoming NOνA experiments. Because of the hierarchy-δ CP degeneracy and the octant-δ CP degeneracy, the impact of hierarchy on octant resolution has to be taken into account. As in the case of hierarchy determination, there exist favorable (unfavorable) values of δ CP for which octant resolution is easy (challenging). However, for octant resolution the unfavorable δ CP values of the neutrino data are favorable for the anti-neutrino data and vice-verse. This is in contrast to the case of hierarchy determination. In this paper, we compute the combined sensitivity of T2K and NOνA to resolve the octant ambiguity. If sin2θ 23 = 0.41, then NOνA can rule out all the values of θ 23 in HO at 2σ C.L., irrespective of the hierarchy and δ CP. Addition of T2K data improves the octant sensitivity. If T2K were to have equal neutrino and anti-neutrino runs of 2.5 years each, a 2σ resolution of the octant becomes possible provided sin2θ 23 ≤ 0.43 or ≥ 0.58 for any value of δ CP.
Journal of High Energy Physics 07/2013; 2013(7). · 5.62 Impact Factor
• Source
##### Article: Resolving the octant of theta23 with T2K and NOvA
[Hide abstract]
ABSTRACT: Preliminary results of MINOS experiment indicate that theta23 is not maximal. Global fits to world neutrino data suggest two nearly degenerate solutions for theta23: one in the lower octant (LO: theta23 < 45 degree) and the other in the higher octant (HO: theta23 > 45 degree). numu to nue oscillations in superbeam experiments are sensitive to the octant and are capable of resolving this degeneracy. We study the prospects of this resolution by the current T2K and upcoming NOvA experiments. Because of the hierarchy-deltacp degeneracy and the octant-deltacp degeneracy, the impact of hierarchy on octant resolution has to be taken into account. As in the case of hierarchy determination, there exist favorable (unfavorable) values of deltacp for which octant resolution is easy (challenging). However, for octant resolution the unfavorable deltacp values of the neutrino data are favorable for the anti-neutrino data and vice-verse. This is in contrast to the case of hierarchy determination. In this paper, we compute the combined sensitivity of T2K and NOvA to resolve the octant ambiguity. If sin^2\theta23 =0.41, then NOvA can rule out all the values of theta23 in HO at 2 sigma C.L., irrespective of the hierarchy and deltacp. Addition of T2K data improves the octant sensitivity. If T2K were to have equal neutrino and anti-neutrino runs of 2.5 years each, a 2 sigma resolution of the octant becomes possible provided sin^2\theta23 \leq 0.43 or \geq 0.58 for any value of deltacp.
01/2013;
• ##### Article: A Novel Approach to Study Atmospheric Neutrino Oscillation
[Hide abstract]
ABSTRACT: We develop a general theoretical framework to analytically disentangle the contributions of the neutrino mass hierarchy, the atmospheric mixing angle, and the CP phase, in neutrino oscillations. To illustrate the usefulness of this framework, especially that it can serve as a complementary tool to neutrino oscillogram in the study of atmospheric neutrino oscillations, we take PINGU as an example and compute muon- and electron-like event rates with event cuts on neutrino energy and zenith angle. Under the assumption of exact momentum measurements of neutrinos with a perfect e-$\mu$ identification and no backgrounds, we find that the PINGU experiment has the potential of resolving the neutrino mass hierarchy and the octant degeneracies within 1-year run, while the measurement of the CP phase is significantly more challenging. Our observation merits a serious study of the detector capability of estimating the neutrino momentum for both muon- and electron-like events.
09/2013;