Understanding the degeneracies in NOνA data

Journal of High Energy Physics, Sep 2018

Abstract The combined analysis of νμ disappearance and νe appearance data of NOνA experiment leads to three nearly degenerate solutions. This degeneracy can be understood in terms of deviations in νe appearance signal, caused by unknown effects, with respect to the signal expected for a reference set of oscillations parameters. We define the reference set to be vacuum oscillations in the limit of maximal θ23 and no CP-violation. We then calculate the deviations induced in the νe appearance signal event rate by three unknown effects: (a) matter effects, due to normal or inverted hierarchy (b) octant effects, due to θ23 being in higher or lower octant and (c) CP-violation, whether δCP ∼ −π/2 or δCP ∼ π/2. We find that the deviation caused by each of these effects is the same for NOνA. The observed number of νe events in NOνA is equivalent to the increase caused by one of the effects. Therefore, the observed number of νe appearance events of NOνA is the net result of the increase caused by two of the unknown effects and the decrease caused by the third. Thus we get the three degenerate solutions. We also find that further data by NOνA can not distinguish between these degenerate solutions but addition of one year of neutrino run of DUNE can make a distinction between all three solutions. The distinction between the two NH solutions and the IH solution becomes possible because of the larger matter effect in DUNE. The distinction between the two NH solutions with different octants is a result of the synergy between the anti-neutrino data of NOνA and the neutrino data of DUNE.

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Understanding the degeneracies in NOνA data

Journal of High Energy Physics September 2018, 2018:36 | Cite as Understanding the degeneracies in NOνA data AuthorsAuthors and affiliations Suman BhartiSuprabh PrakashUshak RahamanS. Uma Sankar Open Access Regular Article - Theoretical Physics First Online: 07 September 2018 Abstract The combined analysis of νμ disappearance and νe appearance data of NOνA experiment leads to three nearly degenerate solutions. This degeneracy can be understood in terms of deviations in νe appearance signal, caused by unknown effects, with respect to the signal expected for a reference set of oscillations parameters. We define the reference set to be vacuum oscillations in the limit of maximal θ23 and no CP-violation. We then calculate the deviations induced in the νe appearance signal event rate by three unknown effects: (a) matter effects, due to normal or inverted hierarchy (b) octant effects, due to θ23 being in higher or lower octant and (c) CP-violation, whether δCP ∼ −π/2 or δCP ∼ π/2. We find that the deviation caused by each of these effects is the same for NOνA. The observed number of νe events in NOνA is equivalent to the increase caused by one of the effects. Therefore, the observed number of νe appearance events of NOνA is the net result of the increase caused by two of the unknown effects and the decrease caused by the third. Thus we get the three degenerate solutions. We also find that further data by NOνA can not distinguish between these degenerate solutions but addition of one year of neutrino run of DUNE can make a distinction between all three solutions. The distinction between the two NH solutions and the IH solution becomes possible because of the larger matter effect in DUNE. The distinction between the two NH solutions with different octants is a result of the synergy between the anti-neutrino data of NOνA and the neutrino data of DUNE. Keywords CP violation Neutrino Physics  ArXiv ePrint: 1805.10182 Download to read the full article text Notes Open Access This article is distributed under the terms of the Creative Commons Attribution License (CC-BY 4.0), which permits any use, distribution and reproduction in any medium, provided the original author(s) and source are credited. References [1] J.N. Bahcall, M.C. Gonzalez-Garcia and C. Pena-Garay, Solar neutrinos before and after neutrino 2004, JHEP 08 (2004) 016 [hep-ph/0406294] [INSPIRE]. [2] SNO collaboration, Q.R. Ahmad et al., Direct evidence for neutrino flavor transformation from neutral current interactions in the Sudbury Neutrino Observatory, Phys. Rev. Lett. 89 (2002) 011301 [nucl-ex/0204008] [INSPIRE]. [3] Super-Kamiokande collaboration, Y. Ashie et al., Evidence for an oscillatory signature in atmospheric neutrino oscillation, Phys. Rev. Lett. 93 (2004) 101801 [hep-ex/0404034] [INSPIRE]. [4] Super-Kamiokande collaboration, R. Wendell et al., Atmospheric neutrino oscillation analysis with sub-leading effects in Super-Kamiokande I, II and III, Phys. Rev. D 81 (2010) 092004 [arXiv:1002.3471] [INSPIRE]. [5] KamLAND collaboration, T. Araki et al., Measurement of neutrino oscillation with KamLAND: Evidence of spectral distortion, Phys. Rev. Lett. 94 (2005) 081801 [hep-ex/0406035] [INSPIRE]. [6] KamLAND collaboration, S. Abe et al., Precision Measurement of Neutrino Oscillation Parameters with KamLAND, Phys. Rev. Lett. 100 (2008) 221803 [arXiv:0801.4589] [INSPIRE]. [7] MINOS collaboration, R. Nichol, Final MINOS Results, talk given at The Neutrino 2012 Conference, June 3-9, 2012, Kyoto, Japan [http://neu2012.kek.jp/]. [8] Daya Bay collaboration, F.P. An et al., Observation of electron-antineutrino disappearance at Daya Bay, Phys. Rev. Lett. 108 (2012) 171803 [arXiv:1203.1669] [INSPIRE]. [9] RENO collaboration, J.K. Ahn et al., Observation of Reactor Electron Antineutrino Disappearance in the RENO Experiment, Phys. Rev. Lett. 108 (2012) 191802 [arXiv:1204.0626] [INSPIRE]. [10] Double CHOOZ collaboration, Y. Abe et al., Reactor electron antineutrino disappearance in the Double CHOOZ experiment, Phys. Rev. D 86 (2012) 052008 [arXiv:1207.6632] [INSPIRE]. [11] I. Esteban, M.C. Gonzalez-Garcia, M. Maltoni, I. Martinez-Soler and T. Schwetz, Updated fit to three neutrino mixing: exploring the accelerator-reactor complementarity, JHEP 01 (2017) 087 [arXiv:1611.01514] [INSPIRE].ADSCrossRefGoogle Scholar [12] T2K collaboration, K. Abe et al., The T2K Experiment, Nucl. Instrum. Meth. A 659 (2011) 106 [arXiv:1106.1238] [INSPIRE]. [13] T2K collaboration, K. Abe et al., Observation of Electron Neutrino Appearance in a Muon Neutrino Beam, Phys. Rev. Lett. 112 (2014) 061802 [arXiv:1311.4750] [INSPIRE]. [14] T2K collaboration, K. Abe et al., Precise Measurement of the Neutrino Mixing Parameter θ 23 from Muon Neutrino Disappearance in an Off-Axis Beam, Phys. Rev. Lett. 112 (2014) 181801 [arXiv:1403.1532] [INSPIRE]. [15] NOνA collaboration, D. Ayres et al., The NOνA Technical Design Report, FERMILAB-DESIGN- (...truncated)


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Suman Bharti, Suprabh Prakash, Ushak Rahaman, S. Uma Sankar. Understanding the degeneracies in NOνA data, Journal of High Energy Physics, 2018, pp. 36, Volume 2018, Issue 9, DOI: 10.1007/JHEP09(2018)036