Physics Beyond the Standard Model I: Neutrino Masses and the Quest for Unification

1. Physics Beyond the Standard Model I:Neutrino Masses and the Quest for Unification K.S. Babu Department of Physics Oklahoma Center for High Energy Physics Oklahoma State University Collider and New Physics Mini-Workshop Natioanal Taiwan University June 10, 2005

2. Outline Neutrino Oscillation Results Interpreting Data • Patterns of Neutrino Mass Spectrum • Neutrinoless Double Beta Decay (bb)0n Tests Theoretical Modeling • Evidence for Unification • Large Neutrino Mixing • Unified Quark-Lepton Description Experimental Tests • Rare Decays t→mg, m→eg • Lepton Dipole Moments • Proton Decay Conclusions

3. Building blocks of matter and carriers of forces

4. A Brief History of Neutrinos • Postulated by Pauli as a desperate measure to restore momentum and energy conservation in beta decay (1930) • Electron type neutrino discovered by Reines and Cowan in reactor experiments (1956) • Muon type neutrino produced in accelerators by Lederman, Schwartz, Steinberger et al (1962) • LEP experiments measure N(nu) = 2.994 +-0.012 (1991-2002) • Neutrinos from the Sun detected by Davis et al (1968) • Neutrinos from Supernova 1987A detected in US and Japan • Neutrino oscillations discovered in atmospheric neutrinos [IMB, Kamiokonde (1988), SuperKamiokande (1998)] • Solar neutrino deficit confirmed by various experiments and interpreted as evidence for neutrino oscillations (1968 –)

6. Solar Neutrinos

8. Solar Neutrino Oscillations Gonzalez-Garcia et al. (2003)

9. Atmospheric Neutrinos

11. L/E Dependence of Atmospheric Neutrinos

12. Atmosphere Neutrino Oscillations Maltoni, et al. hep-ph/0207227

13. SuperKamiokande detector

14. LSND Aguilar, et. al hep-exp/0104049

15. Minkowski (1977) Yanagida (1979) Gell-Mann, Ramond, Slansky (1979) Mohapatra, Senjanovic (1980)

16. Patterns of Neutrino Mass Spectrum

19. Neutrino Mixing versus Quark Mixing Leptons Quarks Disparity a challenge for Quark-Lepton unified theories.

20. (bb)0nand Pattern of Neutrino Masses

21. (meV) Pascoli, Petcov, Rodejohann, hep-ph/0212113

22. Neutrino Masses and the Scale of New Physics from atmospheric neutrino oscillation data Very Close to the GUT scale. Leptogenesis via nR decay explains cosmological baryon asymmetry

23. Evolution of Gauge Couplings Standard Model Supersymmetry K. Dienes, Phys. Rept. (1997)

24. SUSY Spectrum Spin = 0 Spin = 1/2 Spin = 0 Spin = 1/2 Spin = 1 Spin = 1/2

25. Structure of Matter Multiplets

26. Matter Unification in 16 of SO(10)

27. Other Evidences for Unification • Anomaly freedom automatic in many GUTs • Electric charge quantization • Nonzero neutrino masses required in many GUTs • Baryon number violation natural in GUTs – needed for generating cosmological baryon asymmetry • works well for 3rd family

28. SU(5) SO(10) E6 E8 … [SU(3)]3 [SU(5)]2 [SU(3)]4 … GUT Gauge Groups

29. SU(5) GUT Matter multiplets: Higgs: Contain color triplets Yukawa Couplings

30. MSSM Higgs doublets have color triplet partners in GUTs. must remain light must have GUT scale mass to prevent rapid proton decay Doublet-triplet splitting Even if color triplets have GUT scale mass, d=5 proton decay is problematic.

31. Symmetry Breaking Doublet-triplet splitting in SU(5) FINE-TUNED TO O(MW) • The GOOD • Predicts unification of couplings • Uses economic Higgs sector • The BAD • Unnatural fine tuning • Large proton decay rate

32. Nucleon Decay in SUSY GUTs Gauge boson Exchange

33. Higgsino Exchange Sakai, Yanagida (1982) Weinberg (1982)

34. SO(10) GUT Quarks and leptons ~{16i} ContainsnR and Seesaw mechanism Model with Non-renormalizable Yukawa Couplings Higgs: Fits the atmospheric neutrino data well • Small Higgs rep small threshold corrections for gauge couplings • R-parity not automatic (needs a Z2 symmetry)

35. Matter Unification in 16 of SO(10)

36. SUSY SO(10) B-L VEV gives mass to triplets only (DIMOPOULOS-WILCZEK) If 10H only couples to fermions, no d=5 proton decay Doublets from and light 4 doublets, unification upset Add mass term for 10’H

37. Realistic SO(10) Model Pati, Wilczek, KB (1998)

38. Predictions

39. Large Neutrino Mixing with Lopsided Mass Matrices Quark and Lepton Mass hierarchy: This motivates: Albright, KSB and Barr, 1998 Sato and Yanagida, 1998 Irges, Lavignac, Ramond, 1998 Altarelli, Feruglio, 1998 KSB and S. Barr, 1995

40. Example of Lopsided Mass Matrices Gogoladze, Wang, KSB, 2003 Discrete ZN Gauge Symmetry

41. Neutrino Mass Textures Fukugita, Tanimoto, Yanagida, 2003

42. A4 Symmetry and Quasi-degenerate Neutrino E. Ma, 2002 E. Ma, J. Valle, KSB, 2002 With Arbitrary Soft A4 Breaking With Complex parameters, arg(Ue3) = p/2

43. Lepton Flavor Violation and Neutrino Mass Seesaw mechanism naturally explains small n-mass. Current neutrino-oscillation data suggests Flavor change in neutrino-sector Flavor change in charged leptons In standard model with Seesaw, leptonic flavor changing is very tiny.

44. In Supersymmetric Standard model For nR active flavor violation in neutrino sector Transmitted to Sleptons Borzumati, Masiero (1986) Hall, Kostelecky, Raby (1986) Hisano et. al., (1995) SUSY Seesaw Mechanism If B-L is gauged, MR must arise through Yukawa couplings. Flavor violation may reside entirely in f or entirely in Yn

45. Dirac LFV F. Deppisch, et al, hep-ph/0206122

46. If flavor violation occurs only in Dirac Yukawa Yn (with mSUGRA) If flavor violation occurs only inf (Majorana LFV) LFV in the two scenarios are comparable. More detailed study is needed.

47. Majorana LFV Dutta, Mohapatra, KB (2002)

48. LFV in SUSY SO(10) Masiero, Vempati and Vives, hep-ph/0209303

49. Electric Dipole Moments Violates CP Electron: Neutron: Phases in SUSY breaking sector contribute to EDM.

50. SUSY Contributions: A, B are complex in MSSM Effective SUSY Phase