Neutrino Physics III

1. Neutrino Physics III Hitoshi Murayama University of Pisa February 26, 2003

2. Outline • Three Generations • LSND • Implications of Neutrino Mass • Why do we exist? • Models of flavor • Conclusions

3. Three Generations

4. MNS matrix • Standard parameterization of Maki-Nakagawa-Sakata matrix for 3 generations atmospheric solar ???

5. Three-generation • Solar & atmospheric n oscillations easily accommodated within three generations • sin22q23near maximal, Dm2atm ~ 310–3eV2 • sin22q12 large, Dm2solar ~ 510–5eV2 • sin22q13 < 0.05 from CHOOZ, Palo Verde • Because of small sin22q13, solar & atmospheric n oscillations almost decouple • Need to know sin22q13, and mass hierarchy

6. Why do neutrinos have mass at all? Why so small? We have seen mass differences. What are the masses? Wn~mn/15eV Do we need a fourth neutrino? Are neutrinos and anti-neutrinos the same? How do we extend the Standard Model to incorporate massive neutrinos? Raised More Questions

7. 3-flavor mixing • If m1 and m2 not very different, it reduces to the 2-flavor problem

8. When is 3-flavor important? When all masses significantly different Anti-neutrinos: UU*, the last term flips sign Possible CP violation

9. CP Violation • Possible only if: • Dm122, s12 large enough (LMA) • q13 large enough

11. LSND

13. Excess positron events over calculated BG 3.3s Signal

14. LSND unconfirmed Neutrino beam from Fermilab booster Settles the issue of LSND evidence Started data taking the summer 2002 Mini-BooNE

15. LSND Affects SN1987A neutrino burst • Kamiokande’s 11 events: • 1st event is forward may well be ne from deleptonization burst (p e- n ne to become neutron star) • Later events most likely ne • LSND parameters cause complete MSW conversion of nenm if light side (ne lighter) nenm if dark side (ne heavier) • Either mass spectrum disfavored _ _ _ HM, Yanagida

16. LSND Affects SN1987A neutrino burst HM, Yanagida

17. LSND, atmospheric and solar neutrino oscillation signals Dm2LSND ~ eV2 Dm2atm ~ 310–3eV2 Dm2solar < 10–3eV2  Can’t be accommodated with 3 neutrinos  Need a sterile neutrino New type of neutrino with no weak interaction 3+1 or 2+2 spectrum? Sterile Neutrino

18. Sterile Neutrino getting tight • 3+1 spectrum: sin22qLSND=4|U4e|2|U4m|2 • |U4m|2 can’t be big because of CDHS, SK U/D • |U4e|2 can’t be big because of Bugey • Marginally allowed • 2+2 spectrum: past fits preferred • Atmospheric mostly nmnt • Solar mostly nens(or vice versa) • Now pretty much ruled out (Barger et al, Giunti et al, Gonzalez-Garcia et al, Strumia, Maltoni et al)

19. WMAP Maltoni, Schwetz, Tortola, Valle hep-ph/0209368

20. LSND evidence: anti-neutrinos Solar evidence: neutrinos If neutrinos and anti-neutrinos have different mass spectra, atmospheric, solar, LSND accommodated without a sterile neutrino (HM, Yanagida) (Barenboim, Lykken, et al) Best fit to data before KamLAND (Strumia) CPT Violation?“A desperate remedy…”

21. However, now there is an evidence for “solar” oscillation in anti-neutrinos from KamLAND Barenboim, Borissov, Lykken: evidence for atmospheric neutrino oscillation is dominantly for neutrinos. Anti-neutrinos suppressed by a factor of 3. Not a great fit (Strumia) New CPT violation: KamLAND impact

22. CPT Theorem • Based on three assumptions: • Locality • Lorentz invariance • Hermiticity of Hamiltonian • Violation of any one of them: big impact on fundamental physics • Neutrino mass: tiny effect from high-scale physics • Non-local Hamiltonian? (HM, Yanagida) • Brane world? (Barenboim, Borissov, Lykken, Smirnov) • Dipole Field Theory? (Bergman, Dasgupta, Ganor, Karczmarek, Rajesh)

23. Implications on Experiments • Mini-BooNE experiment will not see oscillation in neutrino mode, but will in anti-neutrino mode • Because KamLAND is consistent with LMA, atmospheric neutrino oscillation relies on Dm2LSND ~ eV2 (not a great fit) • Katrin may see endpoint spectrum distortion in t3He+e–+ne  We’ll see! _

24. Maybe even more surprisesin neutrinos!

25. Mass Spectrum What do we do now?

26. (1) Dirac Neutrinos: There are new particles, right-handed neutrinos, after all Why haven’t we seen them? Right-handed neutrino must be very very weakly coupled Why? Two ways to go

27. Extra Dimension • All charged particles are on a 3-brane • Right-handed neutrinos SM gauge singlet  Can propagate in the “bulk” • Makes neutrino mass small (Arkani-Hamed, Dimopoulos, Dvali, March-Russell; Dienes, Dudas, Gherghetta) • Barbieri-Strumia: SN1987A constraint “Warped” extra dimension (Grossman, Neubert) • Or SUSY breaking (Arkani-Hamed, Hall, HM, Smith, Weiner; Arkani-Hamed, Kaplan, HM, Nomura)

28. (2) Majorana Neutrinos: There are no new light particles What if I pass a neutrino and look back? Must be right-handed anti-neutrinos No fundamental distinction between neutrinos and anti-neutrinos! Two ways to go

29. Seesaw Mechanism • Why is neutrino mass so small? • Need right-handed neutrinos to generate neutrino mass , but nR SM neutral To obtain m3~(Dm2atm)1/2, mD~mt, M3~1015GeV (GUT!)

30. electromagnetic, weak, and strong forces have very different strengths But their strengths become the same at 1016 GeV if supersymmetry To obtain m3~(Dm2atm)1/2, mD~mt  M3~1015GeV! Grand Unification M3 Neutrino mass may be probing unification: Einstein’s dream

31. Why do we exist?Matter Anti-matter Asymmetry

32. WMAP Big-Bang NucleosynthesisCosmic Microwave Background (Thuan, Izatov) (Burles, Nollett, Turner)

33. Matter and Anti-MatterEarly Universe 10,000,000,001 10,000,000,000 Matter Anti-matter

34. Matter and Anti-MatterCurrent Universe us 1 Matter Anti-matter The Great Annihilation

35. Sakharov’s Conditionsfor Baryogenesis • Necessary requirements for baryogenesis: • Baryon number violation • CP violation • Non-equilibrium  G(DB>0) > G(DB<0) • Possible new consequences in • Proton decay • CP violation

36. Original GUT Baryogenesis • GUT necessarily breaks B. • A GUT-scale particle X decays out-of-equilibrium with direct CP violation • Now direct CP violation observed: e’! • But keeps B–L0 “anomaly washout” • Also monopole problem

37. Actually, SM converts L to B. In Early Universe (T > 200GeV), W/Z are massless and fluctuate in W/Z plasma Energy levels for left-handed quarks/leptons fluctuate correspon-dingly DL=DQ=DQ=DQ=DB=1  D(B–L)=0 Electroweak Anomaly

38. Two Main Directions • BL0 gets washed out at T>TEW~174GeV • Electroweak Baryogenesis(Kuzmin, Rubakov, Shaposhnikov) • Start with B=L=0 • First-order phase transition  non-equilibrium • Try to create BL0 • Leptogenesis(Fukugita, Yanagida) • Create L0 somehow from L-violation • Anomaly partially converts L to B

39. Leptogenesis • You generate Lepton Asymmetry first. • Generate L from the direct CP violation in right-handed neutrino decay • L gets converted to B via EW anomaly  More matter than anti-matter  We have survived “The Great Annihilation”

40. Does Leptogenesis Work? • Much more details worked out (Buchmüller, Plümacher; Pilaftsis) • ~1010 GeV nR OK • Some tension with supersymmetry because of unwanted gravitino overproduction • Ways around: coherent oscillation of right-handed sneutrino (HM, Yanagida+Hamaguchi)

41. Some tension with supersymmetry: unwanted gravitino overproduction gravitino decay dissociates light nuclei destroys the success of Big-Bang Nucleosynthesis Need TRH<109 GeV Does Leptogenesis Work? • (Kawasaki, Kohri, Moroi)

42. Coherent oscillation of right-handed sneutrino (Bose-Einstein condensate)(HM, Yanagida+Hamaguchi) Inflation ends with a large sneutrino amplitude Starts oscillation dominates the Universe Its decay produces asymmetry Consistent with observed oscillation pattern isocurvature perturbationat WMAP?(Moroi, HM) Leptogenesis Works!

43. Can we prove it experimentally? • We studied this question at Snowmass2001 (Ellis, Gavela, Kayser, HM, Chang) • Unfortunately, no: it is difficult to reconstruct relevant CP-violating phases from neutrino data • But: we will probably believe it if • 0nbb found • CP violation found in neutrino oscillation • EW baryogenesis ruled out Archeological evidences

44. Models of Flavor

45. Question of Flavor • What distinguishes different generations? • Same gauge quantum numbers, yet different • Hierarchy with small mixings:  Need some ordered structure • Probably a hidden flavor quantum number  Need flavor symmetry • Flavor symmetry must allow top Yukawa • Other Yukawas forbidden • Small symmetry breaking generates small Yukawas

46. Fermion Mass Relationin SU(5) • down- and lepton-Yukawa couplings come from the same SU(5) operator 10 5* H • Fermion mass relation mb= mt, ms = mm, md = me @MGUT Reality: mb≈ mt, 3ms ≈ mm, md ≈ 3me @MGUT • Not bad! (small correction compared to inter-generational splitting ~20–200)

47. Broken Flavor Symmetry • Flavor symmetry broken by a VEV ~0.02 • SU(5)-like: • 10(Q, uR, eR) (+2, +1, 0) • 5*(L, dR) (+1, +1, +1) • mu:mc:mt~ md2:ms2:mb2~ me2:mm2:mt2 ~4: 2:1

48. Not bad! • mb~ mt, ms ~ mm, md ~ me @MGUT • mu:mc:mt~ md2:ms2:mb2~ me2:mm2:mt2

49. New Data from Neutrinos • Neutrinos are already providing significant new information about flavor symmetries • If LMA, all mixing except Ue3 large • Two mass splittings not very different • Atmospheric mixing maximal • Any new symmetry or structure behind it?

50. Is There A StructureIn Neutrino Masses & Mixings? • Monte Carlo random complex 33 matrices with seesaw mechanism (Hall, HM, Weiner; Haba, HM)