The mass-hierarchy and CP-violation discovery reach of the LBNO long-baseline neutrino experiment


The next generation neutrino observatory proposed by the LBNO collaboration will address fundamental questions in particle and astroparticle physics. The experiment consists of a far detector, in its first stage a 20 kt LAr double phase TPC and a magnetised iron calorimeter, situated at 2300 km from CERN and a near detector based on a highpressure argon gas TPC. The long baseline provides a unique opportunity to study neutrino flavour oscillations over their 1st and 2nd oscillation maxima exploring the L/E behaviour, and distinguishing effects arising from δ CP and matter.

In this paper we have reevaluated the physics potential of this setup for determining the mass hierarchy (MH) and discovering CP-violation (CPV), using a conventional neutrino beam from the CERN SPS with a power of 750 kW. We use conservative assumptions on the knowledge of oscillation parameter priors and systematic uncertainties. The impact of each systematic error and the precision of oscillation prior is shown. We demonstrate that the first stage of LBNO can determine unambiguously the MH to > 5σ C.L. over the whole phase space. We show that the statistical treatment of the experiment is of very high importance, resulting in the conclusion that LBNO has ~ 100% probability to determine the MH in at most 4-5 years of running. Since the knowledge of MH is indispensable to extract δ CP from the data, the first LBNO phase can convincingly give evidence for CPV on the 3σ C.L. using today’s knowledge on oscillation parameters and realistic assumptions on the systematic uncertainties.

A preprint version of the article is available at ArXiv.


  1. [1]

    A. Stahl et al., Expression of Interest for a very Longc Baseline Neutrino Oscillation experiment (LBNO), CERN-SPSC-2012-021 (2012).

  2. [2]

    S.K. Agarwalla, T. Li and A. Rubbia, An incremental approach to unravel the neutrino mass hierarchy and CP-violation with a long-baseline Superbeam for large θ 13, JHEP 05 (2012) 154 [arXiv:1109.6526] [INSPIRE].

    ADS  Article  Google Scholar 

  3. [3]

    Z. Maki, M. Nakagawa and S. Sakata, Remarks on the unified model of elementary particles, Prog. Theor. Phys. 28 (1962) 870 [INSPIRE].

    ADS  Article  MATH  Google Scholar 

  4. [4]

    B. Pontecorvo, Neutrino experiments and the problem of conservation of leptonic charge, Sov. Phys. JETP 26 (1968) 984 [Zh. Eksp. Teor. Fiz. 53 (1967) 1717] [INSPIRE].

    ADS  Google Scholar 

  5. [5]

    P. Machado, H. Minakata, H. Nunokawa and R. Zukanovich Funchal, Combining accelerator and reactor measurements of θ 13 : the first result, JHEP 05 (2012) 023 [arXiv:1111.3330] [INSPIRE].

    ADS  Article  Google Scholar 

  6. [6]

    G. Fogli, E. Lisi, A. Marrone, D. Montanino, A. Palazzo 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].

    ADS  Google Scholar 

  7. [7]

    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].

    ADS  Google Scholar 

  8. [8]

    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].

    ADS  Article  Google Scholar 

  9. [9]

    F. Piquemal, Reactor neutrinos, double beta and beta decays experimental review, PoS(ICHEP 2010)553.

  10. [10]

    L. Wolfenstein, Neutrino oscillations in matter, Phys. Rev. D 17 (1978) 2369 [INSPIRE].

    ADS  Google Scholar 

  11. [11]

    J. Arafune, M. Koike and J. Sato, CP violation and matter effect in long baseline neutrino oscillation experiments, Phys. Rev. D 56 (1997) 3093 [Erratum ibid. D 60 (1999) 119905] [hep-ph/9703351] [INSPIRE].

    ADS  Google Scholar 

  12. [12]

    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].

    ADS  Google Scholar 

  13. [13]

    LBNE collaboration, C. Adams et al., Scientific opportunities with the long-baseline neutrino experiment, arXiv:1307.7335 [INSPIRE].

  14. [14]

    K. Abe et al., Letter of intent: the Hyper-Kamiokande experimentdetector design and physics potential, arXiv:1109.3262 [INSPIRE].

  15. [15]

    T2K collaboration, K. Abe et al., The T2K neutrino flux prediction, Phys. Rev. D 87 (2013) 012001 [arXiv:1211.0469] [INSPIRE].

    Google Scholar 

  16. [16]

    C. Rubbia, The liquid argon time projection chamber: a new concept for neutrino detectors, CERN-EP-INT-77-08 (1977).

  17. [17]

    A. Rubbia, Experiments for CP-violation: a giant liquid argon scintillation, Cerenkov and charge imaging experiment?, hep-ph/0402110 [INSPIRE].

  18. [18]

    A. Rubbia et al., Underground neutrino detectors for particle and astroparticle science: the Giant Liquid Argon Charge Imaging ExpeRiment (GLACIER), J. Phys. Conf. Ser. 171 (2009) 012020 [arXiv:0908.1286] [INSPIRE].

    Article  Google Scholar 

  19. [19]

    ISS Detector Working Group collaboration, T. Abe et al., Detectors and flux instrumentation for future neutrino facilities, 2009 JINST 4 T05001 [arXiv:0712.4129] [INSPIRE].

    ADS  Google Scholar 

  20. [20]

    A. Cervera, A. Laing, J. Martin-Albo and F. Soler, Performance of the MIND detector at a Neutrino Factory using realistic muon reconstruction, Nucl. Instrum. Meth. A 624 (2010) 601 [arXiv:1004.0358] [INSPIRE].

    ADS  Article  Google Scholar 

  21. [21]

    A. Rubbia, A CERN-based high-intensity high-energy proton source for long baseline neutrino oscillation experiments with next-generation large underground detectors for proton decay searches and neutrino physics and astrophysics, arXiv:1003.1921 [INSPIRE].

  22. [22]

    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].

    Article  Google Scholar 

  23. [23]

    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].

    Article  Google Scholar 

  24. [24]

    T2K collaboration, K. Abe et al., Evidence of electron neutrino appearance in a muon neutrino beam, Phys. Rev. D 88 (2013) 032002 [arXiv:1304.0841] [INSPIRE].

    Google Scholar 

  25. [25]

    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].

    ADS  Article  Google Scholar 

  26. [26]

    K. Elsener et al., The CERN Neutrino beam to Gran Sasso (NGS): conceptual technical design, CERN, Switzerland (1998).

    Google Scholar 

  27. [27]

    E. Shaposhnikova et al., Recent intensity increase in the CERN accelerator chain, CERN-AB-2005-029 (2005).

  28. [28]

    B. Goddard et al., Chamonix 2012 workshop on LHC performance, CERN-ATS-2012-069 (2012).

  29. [29]

    Y. Papaphilippou et al., Design options of a high-power proton synchrotron for LAGUNA-LBNO, in the proceedings of the 4th International Particle Accelerator Conference (IPAC13), May 12-17, Shangai, China (2013).

  30. [30]

    B. Goddard et al., Non-local Fast Extraction from the CERN SPS at 100 and 440 GeV, in the proceedings of the 4th International Particle Accelerator Conference (IPAC13), May 12-17, Shangai, China (2013).

  31. [31]

    V. Papadimitriou, Status of the LBNE Neutrino Beamline, arXiv:1112.0720 [INSPIRE].

  32. [32]

    X. Qian et al., Statistical evaluation of experimental determinations of neutrino mass hierarchy, Phys. Rev. D 86 (2012) 113011 [arXiv:1210.3651] [INSPIRE].

    ADS  Google Scholar 

  33. [33]

    S.-F. Ge, K. Hagiwara, N. Okamura and Y. Takaesu, Determination of mass hierarchy with medium baseline reactor neutrino experiments, JHEP 05 (2013) 131 [arXiv:1210.8141] [INSPIRE].

    ADS  Article  Google Scholar 

  34. [34]

    M. Blennow, P. Coloma, P. Huber and T. Schwetz, Quantifying the sensitivity of oscillation experiments to the neutrino mass ordering, JHEP 03 (2014) 028 [arXiv:1311.1822] [INSPIRE].

    ADS  Article  Google Scholar 

  35. [35]

    A.M. Dziewonski and D.L. Anderson, Preliminary reference earth model, Phys. Earth Planet. Interiors 25 (1981) 297 [INSPIRE].

    ADS  Article  Google Scholar 

  36. [36]

    P. Coloma et al., Precision on leptonic mixing parameters at future neutrino oscillation experiments, JHEP 06 (2012) 073 [arXiv:1203.5651] [INSPIRE].

    ADS  Article  Google Scholar 

  37. [37]

    T. Edgecock et al., High intensity neutrino oscillation facilities in Europe, Phys. Rev. ST Accel. Beams 16 (2013) 021002 [arXiv:1305.4067] [INSPIRE].

    ADS  Article  Google Scholar 

  38. [38]

    M. Ribordy and A.Y. Smirnov, Improving the neutrino mass hierarchy identification with inelasticity measurement in PINGU and ORCA, Phys. Rev. D 87 (2013) 113007 [arXiv:1303.0758] [INSPIRE].

    ADS  Google Scholar 

  39. [39]

    D. Franco et al., Mass hierarchy discrimination with atmospheric neutrinos in large volume ice/water Cherenkov detectors, JHEP 04 (2013) 008 [arXiv:1301.4332] [INSPIRE].

    ADS  Article  Google Scholar 

  40. [40]

    IceCube, PINGU collaboration, M. Aartsen et al., PINGU sensitivity to the neutrino mass hierarchy, arXiv:1306.5846 [INSPIRE].

  41. [41]

    D. Cohen, PINGU and the Neutrino Mass Hierarchy, talk given at the P5 Workshop on the Future of High Energy Physics , December 15-18, Brookhaven National Laboratory, Upton, U.S.A. (2013).

    Google Scholar 

  42. [42]

    KM3NeT collaboration, P. Kooijman, ORCA status report, talk given at the 33rd International Conference of Cosmic Rays (IRC2013), July 2-9, Rio de Janeiro, Brazil (2013).

  43. [43]

    Y.-F. Li, J. Cao, Y. Wang and L. Zhan, Unambiguous determination of the neutrino mass hierarchy using reactor neutrinos, Phys. Rev. D 88 (2013) 013008 [arXiv:1303.6733] [INSPIRE].

    ADS  Google Scholar 

  44. [44]

    A. Balantekin et al., Neutrino mass hierarchy determination and other physics potential of medium-baseline reactor neutrino oscillation experiments, arXiv:1307.7419 [INSPIRE].

  45. [45]

    NOvA collaboration, D. Ayres et al., NOvA: Proposal to build a 30 kiloton off-axis detector to study ν μ ν e oscillations in the NuMI beamline, hep-ex/0503053 [INSPIRE].

  46. [46]

    NOvA collaboration, R. Patterson, The NOvA experiment: status and outlook, Nucl. Phys. Proc. Suppl. 235-236 (2013) 151 [arXiv:1209.0716] [INSPIRE].

    Article  Google Scholar 

Download references

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.

Author information




Corresponding author

Correspondence to A. Rubbia.

Additional information

ArXiv ePrint: 1312.6520

Rights and permissions

Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (, which permits use, duplication, adaptation, distribution, and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made.

Reprints and Permissions

About this article

Verify currency and authenticity via CrossMark

Cite this article

The LAGUNA-LBNO collaboration., Agarwalla, S., Agostino, L. et al. The mass-hierarchy and CP-violation discovery reach of the LBNO long-baseline neutrino experiment. J. High Energ. Phys. 2014, 94 (2014).

Download citation


  • Oscillation
  • Neutrino Detectors and Telescopes
  • CP violation