Octant sensitivity for large θ 13 in atmospheric and long-baseline neutrino experiments

  • Animesh Chatterjee
  • Pomita Ghoshal
  • Srubabati Goswami
  • Sushant K. Raut


One of the unknown parameters in neutrino oscillation studies is the octant of the atmospheric neutrino mixing angle θ 23. In this paper, we discuss the possibility of determining the octant of θ 23 in the long-baseline experiments T2K and NOνA in conjunction with future atmospheric neutrino detectors, in the light of non-zero value of θ 13 measured by reactor experiments. We consider two detector technologies for atmospheric neutrinos — magnetized iron calorimeter and non-magnetized Liquid Argon Time Projection Chamber. We present the octant sensitivity for T2K/NOνA and atmospheric neutrino experiments separately as well as the combined sensitivity. For the long-baseline experiments, a precise measurement of θ 13, which can exclude degenerate solutions in the wrong octant, increases the sensitivity drastically. For θ 23 = 39° and sin2 2θ 13 = 0.1, at least ~ 2σ sensitivity can be achieved by T2K + NOνA for all values of δ CP for both normal and inverted hierarchy. For atmospheric neutrinos, the moderately large value of θ 13 measured in the reactor experiments is conducive to octant sensitivity because of enhanced matter effects. A magnetized iron detector can give a 2σ octant sensitivity for 500 kT yr exposure for θ 23 = 39°, δ CP = 0 and normal hierarchy. This increases to 3σ for both hierarchies by combining with T2K and NOνA. This is due to a preference of different θ 23 values at the minimum χ 2 by T2K/NOνA and atmospheric neutrino experiments. A Liquid Argon type detector for atmospheric neutrinos with the same exposure can give higher octant sensitivity, due to the interplay of muon and electron contributions and superior resolutions. We obtain a ~ 3σ sensitivity for θ 23 = 39° for normal hierarchy. This increases to ≿ 4σ for all values of δ CP if combined with T2K/NOνA. For inverted hierarchy the combined sensitivity is around 3σ.


Neutrino Physics CP violation 


  1. [1]
    DOUBLE-CHOOZ collaboration, Y. Abe et al., Indication for the disappearance of reactor electron antineutrinos in the Double CHOOZ experiment, Phys. Rev. Lett. 108 (2012) 131801 [arXiv:1112.6353] [INSPIRE].ADSCrossRefGoogle Scholar
  2. [2]
    DAYA-BAY collaboration, F. An et al., Observation of electron-antineutrino disappearance at Daya Bay, Phys. Rev. Lett. 108 (2012) 171803 [arXiv:1203.1669] [INSPIRE].ADSCrossRefGoogle Scholar
  3. [3]
    RENO collaboration, J. Ahn et al., Observation of reactor electron antineutrino disappearance in the RENO experiment, Phys. Rev. Lett. 108 (2012) 191802 [arXiv:1204.0626] [INSPIRE].ADSCrossRefGoogle Scholar
  4. [4]
    M. Gonzalez-Garcia, M. Maltoni, J. Salvado and T. Schwetz, Global fit to three neutrino mixing: critical look at present precision, JHEP 12 (2012) 123 [arXiv:1209.3023] [INSPIRE].ADSCrossRefGoogle Scholar
  5. [5]
    G. Fogli et al., Global analysis of neutrino masses, mixings and phases: entering the era of leptonic CP-violation searches, Phys. Rev. D 86 (2012) 013012 [arXiv:1205.5254] [INSPIRE].ADSGoogle Scholar
  6. [6]
    D. Forero, M. Tortola and J. Valle, Global status of neutrino oscillation parameters after Neutrino-2012, Phys. Rev. D 86 (2012) 073012 [arXiv:1205.4018] [INSPIRE].ADSGoogle Scholar
  7. [7]
    T2K collaboration, K. Abe et al., Indication of electron neutrino appearance from an accelerator-produced off-axis muon neutrino beam, Phys. Rev. Lett. 107 (2011) 041801 [arXiv:1106.2822] [INSPIRE].ADSCrossRefGoogle Scholar
  8. [8]
    MINOS collaboration, P. Adamson et al., Improved search for muon-neutrino to electron-neutrino oscillations in MINOS, Phys. Rev. Lett. 107 (2011) 181802 [arXiv:1108.0015] [INSPIRE].ADSCrossRefGoogle Scholar
  9. [9]
    G. Fogli, E. Lisi, A. Marrone, A. Palazzo and A. Rotunno, Hints of θ 13 > 0 from global neutrino data analysis, Phys. Rev. Lett. 101 (2008) 141801 [arXiv:0806.2649] [INSPIRE].ADSCrossRefGoogle Scholar
  10. [10]
    S. Goswami and A.Y. Smirnov, Solar neutrinos and 13 leptonic mixing, Phys. Rev. D 72 (2005) 053011 [hep-ph/0411359] [INSPIRE].ADSGoogle Scholar
  11. [11]
    SNO collaboration, B. Aharmim et al., Combined analysis of all three phases of solar neutrino data from the Sudbury Neutrino Observatory, arXiv:1109.0763 [INSPIRE].
  12. [12]
    KamLAND collaboration, S. Abe et al., Precision measurement of neutrino oscillation parameters with KamLAND, Phys. Rev. Lett. 100 (2008) 221803 [arXiv:0801.4589] [INSPIRE].ADSCrossRefGoogle Scholar
  13. [13]
    MINOS collaboration, P. Adamson et al., Measurements of atmospheric neutrinos and antineutrinos in the MINOS far detector, Phys. Rev. D 86 (2012) 052007 [arXiv:1208.2915] [INSPIRE].ADSGoogle Scholar
  14. [14]
    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].ADSGoogle Scholar
  15. [15]
    G.L. Fogli and E. Lisi, Tests of three flavor mixing in long baseline neutrino oscillation experiments, Phys. Rev. D 54 (1996) 3667 [hep-ph/9604415] [INSPIRE].ADSGoogle Scholar
  16. [16]
    V. Barger, D. Marfatia and K. Whisnant, Breaking eight fold degeneracies in neutrino CP-violation, mixing and mass hierarchy, Phys. Rev. D 65 (2002) 073023 [hep-ph/0112119] [INSPIRE].ADSGoogle Scholar
  17. [17]
    R. Gandhi, P. Ghoshal, S. Goswami, P. Mehta and S.U. Sankar, Earth matter effects at very long baselines and the neutrino mass hierarchy, Phys. Rev. D 73 (2006) 053001 [hep-ph/0411252] [INSPIRE].ADSGoogle Scholar
  18. [18]
    S. Choubey and P. Roy, Probing the deviation from maximal mixing of atmospheric neutrinos, Phys. Rev. D 73 (2006) 013006 [hep-ph/0509197] [INSPIRE].ADSGoogle Scholar
  19. [19]
    K. Abe et al., Letter of intent: the Hyper-Kamiokande experimentDetector design and physics potential, arXiv:1109.3262 [INSPIRE].
  20. [20]
    A. de Bellefon et al., MEMPHYS: a large scale water Cerenkov detector at Frejus, hep-ex/0607026 [INSPIRE].
  21. [21]
    D.J. Koskinen, IceCube-DeepCore-PINGU: fundamental neutrino and dark matter physics at the South Pole, Mod. Phys. Lett. A 26 (2011) 2899 [INSPIRE].ADSGoogle Scholar
  22. [22]
    E.K. Akhmedov, S. Razzaque and A.Y. Smirnov, Mass hierarchy, 23 mixing and CP-phase with huge atmospheric neutrino detectors, JHEP 02 (2013) 082 [arXiv:1205.7071] [INSPIRE].ADSCrossRefGoogle Scholar
  23. [23]
    IceCube collaboration, R. Abbasi et al., The design and performance of IceCube DeepCore, Astropart. Phys. 35 (2012) 615 [arXiv:1109.6096] [INSPIRE].ADSCrossRefGoogle Scholar
  24. [24]
    MONOLITH collaboration, N. Agafonova et al., MONOLITH: a massive magnetized iron detector for neutrino oscillation studies, CERN-SPSC-2000-031 (2000) [INSPIRE].
  25. [25]
    INO collaboration, M.S. Athar et al., India-based Neutrino Observatory: project report. Volume I, INO-2006-01 (2006) [INSPIRE].
  26. [26]
    C. Rubbia et al., Underground operation of the ICARUS T600 LAr-TPC: first results, 2011 JINST 6 P07011 [arXiv:1106.0975] [INSPIRE].
  27. [27]
    ArgoNeuT collaboration, O. Palamara, Neutrino detection in the ArgoNeuT LAr TPC, J. Phys. Conf. Ser. 408 (2013) 012039 [arXiv:1110.3070] [INSPIRE].ADSCrossRefGoogle Scholar
  28. [28]
    A. Ereditato and A. Rubbia, Ideas for future liquid Argon detectors, Nucl. Phys. Proc. Suppl. 139 (2005) 301 [hep-ph/0409143] [INSPIRE].ADSCrossRefGoogle Scholar
  29. [29]
    A. Ereditato and A. Rubbia, Conceptual design of a scalable multi-kton superconducting magnetized liquid Argon TPC, Nucl. Phys. Proc. Suppl. 155 (2006) 233 [hep-ph/0510131] [INSPIRE].ADSCrossRefGoogle Scholar
  30. [30]
    R. Gandhi, P. Ghoshal, S. Goswami and S.U. Sankar, Resolving the mass hierarchy with atmospheric neutrinos using a liquid argon detector, Phys. Rev. D 78 (2008) 073001 [arXiv:0807.2759] [INSPIRE].ADSGoogle Scholar
  31. [31]
    P. Huber, M. Lindner, T. Schwetz and W. Winter, Reactor neutrino experiments compared to superbeams, Nucl. Phys. B 665 (2003) 487 [hep-ph/0303232] [INSPIRE].ADSCrossRefGoogle Scholar
  32. [32]
    K. Hiraide et al., Resolving θ 23 degeneracy by accelerator and reactor neutrino oscillation experiments, Phys. Rev. D 73 (2006) 093008 [hep-ph/0601258] [INSPIRE].ADSGoogle Scholar
  33. [33]
    H. Minakata, H. Sugiyama, O. Yasuda, K. Inoue and F. Suekane, Reactor measurement of θ 13 and its complementarity to long baseline experiments, Phys. Rev. D 68 (2003) 033017 [Erratum ibid. D 70 (2004) 059901] [hep-ph/0211111] [INSPIRE].
  34. [34]
    S. Antusch, P. Huber, J. Kersten, T. Schwetz and W. Winter, Is there maximal mixing in the lepton sector?, Phys. Rev. D 70 (2004) 097302 [hep-ph/0404268] [INSPIRE].ADSGoogle Scholar
  35. [35]
    D. Choudhury and A. Datta, Detecting matter effects in long baseline experiments, JHEP 07 (2005) 058 [hep-ph/0410266] [INSPIRE].ADSCrossRefGoogle Scholar
  36. [36]
    M. Gonzalez-Garcia, M. Maltoni and A.Y. Smirnov, Measuring the deviation of the 23 lepton mixing from maximal with atmospheric neutrinos, Phys. Rev. D 70 (2004) 093005 [hep-ph/0408170] [INSPIRE].ADSGoogle Scholar
  37. [37]
    H. Minakata, M. Sonoyama and H. Sugiyama, Determination of θ 23 in long-baseline neutrino oscillation experiments with three-flavor mixing effects, Phys. Rev. D 70 (2004) 113012 [hep-ph/0406073] [INSPIRE].ADSGoogle Scholar
  38. [38]
    K. Hagiwara and N. Okamura, Solving the degeneracy of the lepton-flavor mixing angle θ ATM by the T2KK two detector neutrino oscillation experiment, JHEP 01 (2008) 022 [hep-ph/0611058] [INSPIRE].ADSCrossRefGoogle Scholar
  39. [39]
    D. Meloni, Solving the octant degeneracy with the Silver channel, Phys. Lett. B 664 (2008) 279 [arXiv:0802.0086] [INSPIRE].ADSGoogle Scholar
  40. [40]
    S.K. Agarwalla, S. Prakash and S.U. Sankar, Resolving the octant of θ 23 with T2K and NOvA, arXiv:1301.2574 [INSPIRE].
  41. [41]
    D. Indumathi, M. Murthy, G. Rajasekaran and N. Sinha, Neutrino oscillation probabilities: Sensitivity to parameters, Phys. Rev. D 74 (2006) 053004 [hep-ph/0603264] [INSPIRE].ADSGoogle Scholar
  42. [42]
    A. Samanta and A.Y. Smirnov, The 23 mixing and mass split: atmospheric neutrinos and magnetized spectrometers, JHEP 07 (2011) 048 [arXiv:1012.0360] [INSPIRE].ADSCrossRefGoogle Scholar
  43. [43]
    V. Barger et al., Neutrino mass hierarchy and octant determination with atmospheric neutrinos, Phys. Rev. Lett. 109 (2012) 091801 [arXiv:1203.6012] [INSPIRE].ADSCrossRefGoogle Scholar
  44. [44]
    L. Wolfenstein, Neutrino oscillations in matter, Phys. Rev. D 17 (1978) 2369 [INSPIRE].ADSGoogle Scholar
  45. [45]
    S.P. Mikheev and A.Y. Smirnov, Resonance amplification of oscillations in matter and spectroscopy of solar neutrinos, Sov. J. Nucl. Phys. 42 (1985) 913 [INSPIRE].Google Scholar
  46. [46]
    S.P. Mikheev and A.Y. Smirnov, Resonant amplification of neutrino oscillations in matter and solar neutrino spectroscopy, Nuovo Cim. C 9 (1986) 17 [INSPIRE].ADSGoogle Scholar
  47. [47]
    J. Burguet-Castell, M. Gavela, J. Gomez-Cadenas, P. Hernández and O. Mena, On the measurement of leptonic CP-violation, Nucl. Phys. B 608 (2001) 301 [hep-ph/0103258] [INSPIRE].ADSCrossRefGoogle Scholar
  48. [48]
    E.K. Akhmedov, R. Johansson, M. Lindner, T. Ohlsson and T. Schwetz, Series expansions for three flavor neutrino oscillation probabilities in matter, JHEP 04 (2004) 078 [hep-ph/0402175] [INSPIRE].ADSCrossRefGoogle Scholar
  49. [49]
    A. Cervera et al., Golden measurements at a neutrino factory, Nucl. Phys. B 579 (2000) 17 [Erratum ibid. B 593 (2001) 731–732] [hep-ph/0002108] [INSPIRE].
  50. [50]
    M. Freund, Analytic approximations for three neutrino oscillation parameters and probabilities in matter, Phys. Rev. D 64 (2001) 053003 [hep-ph/0103300] [INSPIRE].
  51. [51]
    K. Kimura, A. Takamura and H. Yokomakura, Exact formula of probability and CP-violation for neutrino oscillations in matter, Phys. Lett. B 537 (2002) 86 [hep-ph/0203099] [INSPIRE].ADSGoogle Scholar
  52. [52]
    R. Gandhi et al., Mass hierarchy determination via future atmospheric neutrino detectors, Phys. Rev. D 76 (2007) 073012 [arXiv:0707.1723] [INSPIRE].ADSGoogle Scholar
  53. [53]
    A. Dziewonski and D. Anderson, Preliminary reference Earth model, Phys. Earth Planet. Interiors 25 (1981) 297.ADSCrossRefGoogle Scholar
  54. [54]
    A. de Gouvêa, J. Jenkins and B. Kayser, Neutrino mass hierarchy, vacuum oscillations and vanishing |U (e3)—, Phys. Rev. D 71 (2005) 113009 [hep-ph/0503079] [INSPIRE].ADSGoogle Scholar
  55. [55]
    S.K. Raut, Effect of non-zero θ 13 on the measurement of θ 23, arXiv:1209.5658 [INSPIRE].
  56. [56]
    P. Huber, M. Lindner and W. Winter, Simulation of long-baseline neutrino oscillation experiments with GLoBES (General Long Baseline Experiment Simulator), Comput. Phys. Commun. 167 (2005) 195 [hep-ph/0407333] [INSPIRE].ADSCrossRefGoogle Scholar
  57. [57]
    P. Huber, J. Kopp, M. Lindner, M. Rolinec and W. Winter, New features in the simulation of neutrino oscillation experiments with GLoBES 3.0: General Long Baseline Experiment Simulator, Comput. Phys. Commun. 177 (2007) 432 [hep-ph/0701187] [INSPIRE].ADSCrossRefGoogle Scholar
  58. [58]
    M.D. Messier, Evidence for neutrino mass from observations of atmospheric neutrinos with Super-Kamiokande, UMI-99-23965 (1999) [INSPIRE].
  59. [59]
    E. Paschos and J. Yu, Neutrino interactions in oscillation experiments, Phys. Rev. D 65 (2002) 033002 [hep-ph/0107261] [INSPIRE].ADSGoogle Scholar
  60. [60]
    T2K collaboration, T. Nakaya, New results from T2K, talk given at the Neutrino 2012 Conference, June 3–9, Kyoto, Japan (2012).
  61. [61]
    T2K collaboration, Y. Itow et al., The JHF-Kamioka neutrino project, hep-ex/0106019 [INSPIRE].
  62. [62]
    M. Ishitsuka, T. Kajita, H. Minakata and H. Nunokawa, Resolving neutrino mass hierarchy and CP degeneracy by two identical detectors with different baselines, Phys. Rev. D 72 (2005) 033003 [hep-ph/0504026] [INSPIRE].ADSGoogle Scholar
  63. [63]
    P. Huber, M. Lindner and W. Winter, Superbeams versus neutrino factories, Nucl. Phys. B 645 (2002) 3 [hep-ph/0204352] [INSPIRE].ADSCrossRefGoogle Scholar
  64. [64]
    M. Fechner, Study of the expected performance of the T2K experiment on ν/μ-ν/e oscillation using data from the K2K experiment, Ph.D. thesis, Université Paris VI, Paris, France (2006).Google Scholar
  65. [65]
    T2K collaboration, I. Kato, Status of the T2K experiment, J. Phys. Conf. Ser. 136 (2008) 022018 [INSPIRE].ADSCrossRefGoogle Scholar
  66. [66]
    NOνA collaboration, R. Patterson, The noνa experiment: status and outlook, talk given at the Neutrino 2012 Conference, June 3–9, Kyoto, Japan (2012).
  67. [67]
    S.K. Agarwalla, S. Prakash, S.K. Raut and S.U. Sankar, Potential of optimized NOvA for large θ (13) and combined performance with a LArTPC and T2K, JHEP 12 (2012) 075 [arXiv:1208.3644] [INSPIRE].ADSCrossRefGoogle Scholar
  68. [68]
    A. Ghosh, T. Thakore and S. Choubey, Determining the neutrino mass hierarchy with INO, T2K, NOvA and reactor experiments, JHEP 04 (2013) 009 [arXiv:1212.1305] [INSPIRE].ADSCrossRefGoogle Scholar
  69. [69]
    INO collaboration, S. Choubey, Future of atmospheric neutrino measurements, talk given at the Neutrino 2012 Conference, June 3–9, Kyoto, Japan (2012).
  70. [70]
    M. Gonzalez-Garcia and M. Maltoni, Atmospheric neutrino oscillations and new physics, Phys. Rev. D 70 (2004) 033010 [hep-ph/0404085] [INSPIRE].ADSGoogle Scholar
  71. [71]
    G. Fogli, E. Lisi, A. Marrone, D. Montanino and A. Palazzo, Getting the most from the statistical analysis of solar neutrino oscillations, Phys. Rev. D 66 (2002) 053010 [hep-ph/0206162] [INSPIRE].ADSGoogle Scholar
  72. [72]
    G. Fogli, E. Lisi, A. Marrone and D. Montanino, Status of atmospheric ν(μ) → ν(τ) oscillations and decoherence after the first K2K spectral data, Phys. Rev. D 67 (2003) 093006 [hep-ph/0303064] [INSPIRE].ADSGoogle Scholar
  73. [73]
    D. Indumathi and M. Murthy, A question of hierarchy: matter effects with atmospheric neutrinos and anti-neutrinos, Phys. Rev. D 71 (2005) 013001 [hep-ph/0407336] [INSPIRE].ADSGoogle Scholar
  74. [74]
    S. Petcov and T. Schwetz, Determining the neutrino mass hierarchy with atmospheric neutrinos, Nucl. Phys. B 740 (2006) 1 [hep-ph/0511277] [INSPIRE].ADSCrossRefGoogle Scholar
  75. [75]
    A. Samanta, Discrimination of mass hierarchy with atmospheric neutrinos at a magnetized muon detector, Phys. Rev. D 81 (2010) 037302 [arXiv:0907.3540] [INSPIRE].ADSGoogle Scholar
  76. [76]
    M. Blennow and T. Schwetz, Identifying the neutrino mass ordering with INO and NOvA, JHEP 08 (2012) 058 [Erratum ibid. 1211 (2012) 098] [arXiv:1203.3388] [INSPIRE].

Copyright information

© SISSA, Trieste, Italy 2013

Authors and Affiliations

  • Animesh Chatterjee
    • 1
  • Pomita Ghoshal
    • 2
  • Srubabati Goswami
    • 2
  • Sushant K. Raut
    • 2
  1. 1.Harish-Chandra Research InstituteJhunsiIndia
  2. 2.Physical Research LaboratoryNavrangpuraIndia

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