Question of hierarchy: Matter effects with atmospheric neutrinos and antineutrinos

Indumathi, D.; Murthy, M. V. N.

doi:10.1103/physrevd.71.013001

Cited by 75 publications

(104 citation statements)

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“…If θ 13 were significantly nonzero, then one could use the presence or absence of the resonance to discern which hierarchy is realized by nature. To do so, one would either need to have a relatively pure neutrino (or antineutrino) source or a detector, such as a magnetized iron calorimeter, which could distinguish neutrino from antineutrino [25,34,35,41,42]. Unfortunately, the atmospheric neutrino and anti-neutrino spectra are roughly equivalent, and water Cerenkov detectors, like Super-K, cannot resolve neutrino from anti-neutrino.…”

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confidence: 99%

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Impact of hierarchy upon the values of neutrino mixing parameters

Escamilla-Roa¹,

Latimer²,

Ernst³

2010

Phys. Rev. C

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A neutrino-oscillation analysis is performed of the more finely binned Super-K atmospheric, MI-NOS, and CHOOZ data in order to examine the impact of neutrino hierarchy in this data set upon the value of θ13 and the deviation of θ23 from maximal mixing. Exact oscillation probabilities are used, thus incorporating all powers of θ13 and ε := θ23 − π/4. The extracted oscillation parameters are found to be dependent on the hierarchy, particularly for θ13. We find at 90% CL are ∆32 = 2.44 +0.26 −0.20 and 2.48 +0.25 −0.22 × 10 −3 eV 2 , ε = θ23 − π/4 = 0.06 +0.06 −0.16 and 0.06 +0.08 −0.17 , and θ13 = −0.07 +0.18 −0.11 and −0.13 +0.23 −0.16 , for the normal and inverted hierarchy respectively. The inverted hierarchy is preferred at a statistically insignificant level of 0.3 σ.PACS numbers: 14.60.Pq Keywords: neutrino oscillations, three neutrinos, mixing angles, mass-squared differences, mass hierarchyThe field of neutrino oscillations has progressed rapidly over the past fifteen years. The data can largely be understood by the oscillation of the three known neutrinos [1, 2]. Oscillation phenomenology invokes a unitary matrix that relates the flavor basis, in which the neutrinos are created or destroyed, to the mass basis, in which the neutrinos propagate through vacuum. This matrix can be written in terms of three real mixing angles, θ 12 , θ 23 , and θ 13 , and a phase δ that determines CP violation. Oscillations also require nonzero neutrino mass differences, being dependent upon the difference of the square of the masses, ∆ ij := m 2 i − m 2 j with m i the mass of neutrino i. A recent analysis [3] reports the present knowledge of the values of the oscillation parameters. In particular, we note that only an upper limit exists on the size of the "reactor" mixing angle |θ 13 | = 0.19 +0.12 −0.19 (1σ), a constraint which arises, in part, from the null oscillation result of the CHOOZ experiment [4]. A nonzero value of θ 13 is requisite for the existence of CP violation in neutrino oscillations; hence, we presently have no knowledge of the value of δ. We also have no knowledge of the ordering of the neutrino mass eigenstate; namely, is m 3 greater or less than m 1 and m 2 ? The former (latter) situation is termed the normal (inverted) hierarchy.Recently, hints of nonzero θ 13 have been reported as a means by which to ease the tension between the determination of the oscillation parameters θ 12 and ∆ 21 by the solar and KamLAND experiments [5,6]. At a smaller significance, analyses of atmospheric data also hint at nonzero θ 13 [7,8], though one study shows that the significance of the results are dependent upon the precise nature of the statistical analysis [9]. Furthermore, an analysis of the updated atmospheric data finds no preference for nonzero θ 13 [10]; however, this analysis employs approximate oscillation formulae and cannot be directly compared to these other works. Should these various hints be cleanly confirmed in current neutrino oscillation experiments [11-13], then one might be able to attack the issue of C...

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confidence: 99%

“…In the near future, the T2K [28] and NOνA [29] experiments may be able to determine the hierarchy [30][31][32][33]. Atmospheric neutrinos experiments can certainly be of some use in unraveling these unknowns as upgoing neutrinos travel through the earth over a large range of baselines and energies [25,[34][35][36][37][38][39][40][41][42]. In Ref.…”

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confidence: 99%

Impact of hierarchy upon the values of neutrino mixing parameters

Escamilla-Roa¹,

Latimer²,

Ernst³

2010

Phys. Rev. C

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“…The key point to note is that there is very little sensitivity to δ CP over the relevant E, θ zenith range. Matter effects are therefore sensitive to the mass ordering of the 2-3 states [15,16,17], provided θ 13 is sufficiently large; as has now been established by the reactor neutrino experiments [4]. Fig.…”

Section: Mass Ordering With Muons Alonementioning

confidence: 99%

India-based neutrino observatory (INO): Physics reach and status report

Indumathi

2015

AIP Conference Proceedings

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The India-based Neutrino Observatory (INO) is a proposed underground facility located in India that will primarily house the magnetised Iron CALorimeter (ICAL) detector to study atmospheric neutrinos produced by interactions of cosmic rays with Earth's atmosphere. The physics goal is to to make precision measurements of the neutrino mixing and oscillation parameters through such a study. We present here the results from detailed simulations studies, as well as a status report on the project. In particular, we highlight the sensitivity of ICAL to the open issue of the neutrino mass ordering, which can be determined independent of the CP phase at ICAL.

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“…However, the fact that θ 13 has turned to be relatively large might prove counter-productive for the CP violation searches. The reason mainly being that the CP violation effects in the appearance channel become further sub-dominant compared to the main CP independent θ 13 driven oscillations for such large values of θ 13 . This makes the latter an irreducible background, decreasing thereby the sensitivity of the experiment for CP searches [6,7].…”

Section: Introductionmentioning

confidence: 99%

“…CP violation in neutrino oscillations is necessarily a sub-leading effect and is expected to be be in the θ 13 -driven appearance channel, P µe . Therefore, it is necessary to have a non-zero θ 13 for the measurement of the CP phase. However, the fact that θ 13 has turned to be relatively large might prove counter-productive for the CP violation searches.…”

Section: Introductionmentioning

confidence: 99%

Measuring the mass hierarchy with muon and hadron events in atmospheric neutrino experiments

Ghosh

Choubey

2013

J. High Energ. Phys.

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Neutrino mass hierarchy can be measured in atmospheric neutrino experiments through the observation of earth matter effects. Magnetized iron calorimeters have been shown to be good in this regard due to their charge identification capabilities. The charged current interaction of ν µ in this detector, produces a muon track and a hadron shower. The direction of the muon track can be measured very accurately. We show the improvement expected in the reach of this class of experiments to the neutrino mass hierarchy, as we improve the muon energy resolution and the muon reconstruction efficiency. We next propose to include the hadron events in the analysis, by tagging them with the zenith angle of the corresponding muon and binning the hadron data first in energy and then in zenith angle. To the best of our knowledge this way of performing the analysis of the atmospheric neutrino data has not be considered before. We show that the hadron events increase the mass hierarchy sensitivity of the experiment. Finally, we show the expected mass hierarchy sensitivity in terms of the reconstructed neutrino energy and zenith angle. We show how the detector resolutions spoil the earth matter effects in the neutrino channel and argue why the sensitivity obtained from the neutrino analysis cannot be significantly better than that obtained from the analysis using muon data alone. As a result, the best mass hierarchy sensitivity is obtained when we add the contribution of the muon and the hadron data. For sin 2 2θ 13 = 0.1, sin 2 θ 23 = 0.5, a muon energy resolution of 2%, reconstruction efficiency of 80% and exposure of 50 × 10 kton-year, we could get up to 4.5σ signal for the mass hierarchy from combining the muon and hadron data. The signal will go up when the atmospheric data is combined with data from other existing experiments, particularly NOνA.

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Question of hierarchy: Matter effects with atmospheric neutrinos and antineutrinos

Cited by 75 publications

References 27 publications

Impact of hierarchy upon the values of neutrino mixing parameters

Impact of hierarchy upon the values of neutrino mixing parameters

India-based neutrino observatory (INO): Physics reach and status report

Measuring the mass hierarchy with muon and hadron events in atmospheric neutrino experiments

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