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Neutrinos and the Flavour Puzzle: A Mini-Review

Neutrinos and the Flavour Puzzle: A Mini-Review. Stefan Antusch. University of Basel Department of Physics. Max-Planck- Institut für Physik (Werner-Heisenberg-Institut ). Review talk at EPS-HEP 2011. July 22, 2011. The Neutrino Flavour Puzzles.

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Neutrinos and the Flavour Puzzle: A Mini-Review

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  1. Neutrinos and the Flavour Puzzle: A Mini-Review Stefan Antusch University of BaselDepartment of Physics Max-Planck-Institutfür Physik(Werner-Heisenberg-Institut) Review talk at EPS-HEP 2011 July 22, 2011

  2. The Neutrino Flavour Puzzles Neutrino masses:Why so small? How to extend the SM? Lepton mixing:Why so large? (TB?)

  3. Many open neutrino questions … • What are the values of θ13, δ, sgn(Δm312)? • What is the absolute neutrino mass scale? • Are neutrino masses of Dirac or Majorana type? • If Majorana, what are the values of the Majorana phases? • Precise values of all leptonic mixing angles? Such open questions are great! It means we can still make predictions ... !

  4. The Neutrino Flavour Puzzle #1 Neutrino masses:Why so small? How to extend the SM?

  5. mν MR ... in model building, most approaches are based on: ΣR (type I or III) At which scale? Is it a tree-level “Seesaw”? • At high scale (~ MGUT) • At TeV scale (→ colliders, LHC) • (C) At eV energies (light sterile ν’s) P. Minkowski ('77), Mohapatra, Senjanovic, Yanagida, Gell-Mann, Ramond, Slansky, Schechter, Valle, Magg, Wetterich, Ma, Foot, Lew, He, Joshi, ...

  6. mν MR Dirac neutrinos string theory string theory ?... or something completely different R

  7. ... to find answers we need to combine data from various sources: indirect tests (e.g. LFV,universality, non-unitarity) Colliders (LHC) Best chances for TeVscale mass generation: 0νββ decay,Tritium β decay, cosmology → talk by Alessandro Strumia (tomorrow)

  8. The Neutrino Flavour Puzzle #2 Lepton mixing:Why so large? (TB?)

  9. I) Preliminary remark: Large mixing is no fixed point of the RG evolution → There is no unbroken symmetry to enforce TB mixing! RGEs for the mixing angles (in LO): S.A., Kersten, Lindner, Ratz (‘03)

  10. Identify remnant symmetries!GFam generated by S,T and U→ S4 family symmetry I) “Direct” models: A4 possible as wellfor certain selection of field reps GFam Generator T broken but S,U preserved! Generators S, U broken but T preserved! NeutrinoSector Charged LeptonSector UTB Altarelli, Feruglio, Ma, Hagedorn, Merlo, Luhn ... S4 preferred: Lam

  11. II) “Indirect” models: ‘Direct’ vs. ‘indirect’ models:King, Luhn (‘09) Dynamical fields = Flavons ~ A, B, Cin 3 of GFam generate flavour structure in the neutrino sector GFam typically broken completely in mν→ vacuum alignment crucial King, Ross, de Medeiros Varzielas, Malinsky, Chen, ...

  12. Both approaches point to non-Abelian discrete family symmetries GFam! Various successful models have been constructed by many authors (too manyto review them all in a mini-review) ...!

  13. → talk by Michele Maltoni Finally, if T2K gets confirmed:Is TB mixing still the right LO mixing pattern? T2K collaboration (2011) → talk by Claudio Gigante

  14. The flavour puzzle:(At least) four aspects

  15. We should not forget the other pieces of the flavour puzzle! I) The neutrino flavour puzzle II) The SM flavour puzzle IV) The puzzle of CP violation III) The “new physics” flavour puzzle

  16. Example from the SM flavour puzzle: Why are the masses of down-type quarks and charged leptons so similar?

  17. Example from the SM flavour puzzle mb ↔ mτ ? ms ↔ mμ ? (running masses at the top-mass scale; errors are 3 times the 1σ errors ...)

  18. Mass relations are predictions of unified models [1] Georgi, Jarlskog (‘79) [2]S.A., Spinrath (‘09) [3] Allanach, King (‘96) [1] [2] [2] [2] [3] [3] In SUSY GUTs the viability depends on SUSY parameters: → testable @ colliders!

  19. GUT relations also affect predictions for MNS mixing parameters! • Consequencs: Lepton mixing sum rule relations,prediction for θ13, predictions for the Dirac CP phase δMNS! Mu Md GUT relation e.g.: Uν+ = UTB mν Me CP violation

  20. More generally in GUTs, when charged lepton corrections dominate ... Mu Md GUT relations e.g.: Uν+ = UTB mν Me Novel Clebsch factors for viable GUT mass relations → can lead to large θ13MNS(e.g. θ13MNS ≈ 7.6° or ≈ 10°)S.A., Maurer (’11) 1) Prediction for θ13MNS(for )

  21. More generally in GUTs, when charged lepton corrections dominate ... Mu Md GUT relation e.g.: Uν+ = UTB mν Me King (’05); Masina (’05); S.A., King (‘05) 2) Lepton mixing sum rule (for )

  22. → δMNS ≈ 180°, θ13MNS≈ 10° For large θ13MNS → δMNS ≈ 90°,270° from S.A., Huber, King, Schwetz (’07) 2) Lepton mixing sum rule (for )

  23. GUT symmetries unify “vertically”, family symmetries unify “horizontally” GUTs x Family symmetries are a poweful framework for approaching the flavour puzzle!

  24. The flavour puzzle with “new physics” What is the flavour structure of the new physics (if exists @ TeV energies)?

  25. Supersymmetry: For each SM particle there is a supersymmetric “partner particle”. SUSY is broken: The SUSY particles have their own flavour structure The flavour puzzle would get a “new dimension”: What is the flavour structure of the SUSY particles?

  26. Family symmetries: Can solve SUSY flavour problem! • Explain flavour structure in the SM, e.g.: • Generate flavour stucture of the SUSY particles: In particular: Non-Abelian family symmetries! Abel, Khalil, Lebedev (’01)Ross, Vives (‘02),Ross, Velasco-Sevilla, Vives (‘04)S.A., King, Malinsky (‘07)... Remaining tension can be resolved in SUGRA: S.A., King, Ross, Malinsky (’08) SUSY flavour structure related to the one of the SM Family symmetry!

  27. Altmanns-hofer, Buras,Gori, Paradisi,Straub (‘09) Flavour physics effects = “DNA“ of flavour models

  28. The puzzle of CP violation Why is the unitary triangle right-angled?

  29. The unitarity triangle: Fit to the experimental data Observation: The angle α ≈ 90° ... just an accident?

  30. The unitarity triangle: Fit to the experimental data Recent development: New unified flavour models with GFam plus Z2 or Z4 shaping symmetries (& spont. CP viol.): → can explain α = 90° by realising the “phase sum rule”→ δMNS ∈ {0°,90°,180°,270°} S.A., King, Luhn, Spinrath (‘11) Observation: The angle α ≈ 90° ... just an accident? → poster by Martin Spinrath

  31. Challenge for flavour models: Resolve all aspects of the flavour puzzle! I) The neutrino flavour puzzle II) The SM flavour puzzle IV) The puzzle of CP violation III) The “new physics” flavour puzzle

  32. Thanks for your attention!

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