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Perspectives from Neutrinos

Perspectives from Neutrinos. Hitoshi Murayama (UC Berkeley) TAU2002 Santa Cruz, September 12, 2002. The Question. So much activity on neutrino oscillation. Why are we doing this? Window to beyond the Standard Model!. Why Beyond the Standard Model.

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Perspectives from Neutrinos

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  1. Perspectives from Neutrinos Hitoshi Murayama (UC Berkeley) TAU2002 Santa Cruz, September 12, 2002

  2. The Question • So much activity on neutrino oscillation. Why are we doing this? Window to beyond the Standard Model! Hitoshi Murayama TAU2002

  3. Why Beyond the Standard Model • Standard Model is sooooo successful. But none of us are satisfied with the SM. Why? • Because it leaves so many great questions unanswered  Drive to go beyond the Standard Model • Two ways: • Go to high energies • Study rare, tiny effects  Hitoshi Murayama TAU2002

  4. Big Questions • Charge quantization, anomaly cancellation, bizarre hypercharge assignments in the Standard Model • Why are there three seemingly unrelated forces yet all gauge forces? • Is there a unified description of all forces as Einstein dreamed about? • Why is mW<<MPl? (Hierarchy Problem) Why are there three generations? • Why physics determines the pattern of masses and mixings? • What is the origin of CP violation? • What is the origin of matter anti-matter asymmetry in Universe? Hitoshi Murayama TAU2002

  5. Rare Effects from High-Energies • Effects of physics beyond the SM as effective operators • Can be classified systematically (Weinberg) Hitoshi Murayama TAU2002

  6. Unique Role of Neutrino Mass • Lowest order effect of physics at short distances • Tiny effect (mn/En)2~(eV/GeV)2=10–18! • Inteferometry (i.e., Michaelson-Morley)! • Need coherent source • Need interference (i.e., large mixing angles) • Need long baseline Nature was kind to provide all of them! • “neutrino interferometry” (a.k.a. neutrino oscillation) a unique tool to study physics at very high scales Hitoshi Murayama TAU2002

  7. March 2002 April 2002 with SNO Hitoshi Murayama TAU2002

  8. Historic Era in Neutrino Physics • Atmospheric nm is lost (>10s), converted mostly likely to nt(>99%CL) (SK, MACRO) • Solar ne is converted to either nm or nt(>5.3s) (SNO) • No dark side in solar neutrinos ;-( • Explanation is probably neutrino oscillation • Other possibilities: Neutrino decay, Violation of equivalence principle, spin resonant rotation, FCNC • Possible, but models tend to be ugly • Tiny neutrino mass: the first evidence for incompleteness of Minimal Standard Model Hitoshi Murayama TAU2002

  9. Now what? • We are pretty much convinced that neutrinos have mass. Now what? • What did we learn? • What do we want to know more? • Why are still working on neutrinos? • Any connection to quark sector? • Any connection to cosmology? Hitoshi Murayama TAU2002

  10. Outline • Introduction • Implications of Neutrino Mass • Baryon Asymmetry • Neutrino and B connection • Conclusions Hitoshi Murayama TAU2002

  11. Implications of Neutrino Mass

  12. Neutrinos are Left-handed Hitoshi Murayama TAU2002

  13. Neutrinos must be Massless • All neutrinos left-handed  massless • If they have mass, can’t go at speed of light. • Now neutrino right-handed??  contradiction  can’t be massive Hitoshi Murayama TAU2002

  14. Standard Model • We have seen only left-handed neutrinos and right-handed anti-neutrinos (CPT) • Neutrinos are strictly massless in the Standard Model Finite mass of neutrinos implies that the Standard Model is incomplete! • Not just incomplete but probably a lot more profound Hitoshi Murayama TAU2002

  15. Mass Spectrum What do we do now? Hitoshi Murayama TAU2002

  16. (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 Hitoshi Murayama TAU2002

  17. Extra Dimensions • 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; Grossman, Neubert) • mn ~ 1/R if one extra dim  R~10mm • An infinite tower of sterile neutrinos • Or SUSY breaking (Arkani-Hamed, Hall, HM, Smith, Weiner) Hitoshi Murayama TAU2002

  18. (2) Majorana Neutrinos: There are no new light particles Why if I pass a neutrino and look back? Must be right-handed anti-neutrinos No fundamental distinction between neutrinos and anti-neutrinos!  0nbb Two ways to go Hitoshi Murayama TAU2002

  19. 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!) Hitoshi Murayama TAU2002

  20. 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 Hitoshi Murayama TAU2002

  21. RGE analysis SuperK limit MHc>7.6 1016 GeV Even if 1st, 2nd generation scalars “decoupled”, 3rd generation contribution (Goto, Nihei) MHc>5.7 1016 GeV (HM, Pierce) Rest In PeaceMinimal SUSY SU(5) GUT Hitoshi Murayama TAU2002

  22. Avoiding Proton Decay • Unfortunately, proton decay rate/mode is highly model-dependent • more threshold corrections (HM, Pierce) • Some fine-tuning (Babu, Barr) • GUT breaking by orbifolds (Kawamura; Hall, Nomura) • Depends on the triplet-doublet splitting mechanism, Yukawa (non-)unification • Many modified models predict decay rate within 10–100 beyond limit Don’t give up! Hitoshi Murayama TAU2002

  23. Of course, we need to see SUSY directly Once found, their masses tell us if unification is true (LHC and LC combined) Superpartners as probe Hitoshi Murayama TAU2002

  24. Baryon Asymmetry

  25. “Crisis” the past few years Thuan-Izotov reevaluation of 4He abundance Sangalia D abundance probably false Now concordance (Thuan, Izatov), (Burles, Nollett, Turner) Big-Bang Nucleosynthesis Hitoshi Murayama TAU2002

  26. Cosmic Microwave Background Hitoshi Murayama TAU2002

  27. Baryon AsymmetryEarly Universe 10,000,000,001 10,000,000,000 They basically have all annihilated away except a tiny difference between them Hitoshi Murayama TAU2002

  28. Baryon AsymmetryCurrent Universe us 1 They basically have all annihilated away except a tiny difference between them Hitoshi Murayama TAU2002

  29. 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 Hitoshi Murayama TAU2002

  30. Actually, SM violates B (but not B–L). 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 Anomaly washout Hitoshi Murayama TAU2002

  31. 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 Hitoshi Murayama TAU2002

  32. Leptogenesis • You generate Lepton Asymmetry first. • L gets converted to B via EW anomaly • Fukugita-Yanagida: generate L from the direct CP violation in right-handed neutrino decay Hitoshi Murayama TAU2002

  33. Leptogenesis • Two generations enough for CP violation because of Majorana nature (choose 1 & 3) • Right-handed neutrinos decay out-of-equilibrium • Much more details worked out in light of oscillation data (Buchmüller, Plümacher; Pilaftsis) • M1~1010 GeV OK  want supersymmetry Hitoshi Murayama TAU2002

  34. Some tension with supersymmetry: unwanted gravitino overproduction Thermal production (TRH<109 GeV) Non-thermal production from preheating (TRH<105 GeV?) (Giudice, Riotto, Tkachev) Does Leptogenesis Work? • (Kawasaki, Kohri, Moroi) Hitoshi Murayama TAU2002

  35. 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 Possible imprint on CMBR (Moroi) Leptogenesis Works! Hitoshi Murayama TAU2002

  36. Preheating • Oscillating inflaton f (mass ~1013GeV) • The coupling to right-handed neutrino (M+gf)NN • Mass vanishes at f=M/g  non-adiabatic  explosive production up to 1017GeV (Giudice, Riotto, Tkachev) • The case of SUSY more subtle because f complex (Chacko, HM, Perelstein) • Nonetheless can produce N up to 1015GeV Hitoshi Murayama TAU2002

  37. CP Violation • Possible only if: • Dm122, s12 large enough (LMA) • q13 large enough • Can we see CP violation?  KamLAND  JHF, OANuMI?  ? May need better parameter determination using solar pp neutrinos Hitoshi Murayama TAU2002

  38. 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 alone • But: we will probably believe it if • 0nbb found • CP violation found in neutrino oscillation • EW baryogenesis ruled out Archeological evidences Hitoshi Murayama TAU2002

  39. Do we need seesaw? • Natural explanation for small neutrino mass • Seesaw: mn~<H>2/M • What about hn~mSUSY/M? (Arkani-Hamed, Hall, HM, Smith, Weiner) (Borzumati, Nomura) • Suppresses neutrino Yukawa coupling • Naturally light Dirac neutrinos • Light right-handed neutrinos Hitoshi Murayama TAU2002

  40. Small Neutrino MassFrom SUSY Breaking • <c>~mSUSY+q2mSUSYMPl breaks SUSY and U(1)N, preserves U(1)L+N • Heavy vector-like lepton doublets F, F* • Coupling: MFF*+ cLF*+FNHu (HM, Pierce) • Most general couplings allowed by lepton number and U(1)N number • Exchange of F generates • <c>LNHu/M • Small Yukawa <c>/M • Large and mixing (interesting for LHC/LC) Hitoshi Murayama TAU2002

  41. Heavy doublets decay to FcL or NHu Decay produces asymmetry (≥2 gener.) Ln+LN=0, but Ln =–LN0 LN0 protected because of small Yukawa Ln partially converted to B Practially only now (T ~ mn~ 103 K),Ln & LN equilibriate, but do not cancel any more (Dick, Lindner, Ratz, Wright) The explanation for small neutrino mass provides the origin of baryon asymmetry! (HM, Pierce) Dirac Leptogenesis Hitoshi Murayama TAU2002

  42. Neutrino and B connection

  43. Large mixing between nt and nm Make it SU(5) Then a large mixing between sR and bR Mixing among right-handed fields drop out from CKM matrix But mixing among superpartners physical Interesting effects in bs transition? Constraints from meg etc prevent effects >10% if nR all degenerate Goto, Okada, Shimizu, Shindou, Tanaka; Moroi In naïve SO(10), O(1) effects on bs transition possible Chang, Masiero, HM Large q23 and quarks Hitoshi Murayama TAU2002

  44. CP violation in Bs mixing (BsJ/yf) (Chang, Masiero, HM) Addt’l CP violation in penguin bs (BdfKs) (Chang, Masiero, HM) Consequences in B physics Hitoshi Murayama TAU2002

  45. ICHEP 2002 @ Amsterdam “sin2f1”=–0.73±0.64±0.18 (Belle) “sin2b”=–0.19±0.51±0.09 (BABAR) Compared to W. A. from J/y Ks +0.731±0.055 Maybe a hint (~2.7s) of SUSY flavor physics? But BdhKs, K+K–Ks? Even if the current “discrepancy” disappears, it remains true that this is a very reasonable place for new physics to show up. Bdf Ks Hitoshi Murayama TAU2002

  46. Conclusions • Neutrino physics going through a revolution • Naturally small neutrino mass requires major plumbing in the theory • GUT/seesawMajorana neutrino • Extra D/SUSY breakingDirac neutrino • Leptogenesis gaining momentum • Many viable models (coherent oscillation, preheating) • Majorana neutrino not mandatory • Interesting possible consequences of neutrino mixing in bs • through GUT, models of flavor • Need truly multi-prong approach • Energy frontier, flavor experiment, non-accelerator experiments

  47. Signals of Electroweak Baryogenesis • ~20% enhancements to Dmd, Dms with the same phase as in the SM (HM, Pierce) • Find Higgs, stop, charginos (Tevatron?) • Eventually need to measure the phase in the chargino sector at LC to establish it Hitoshi Murayama TAU2002

  48. (HM, Pierce) Hitoshi Murayama TAU2002

  49. B-physics Challenges • Lattice QCD: need B parameters at 5%  then Bs mixing in business • Vtd has been determined from B mixing Not legitimate in presence of SUSY loop • Need to determine Vtd from other sides, angles Vub (from q2 distribution?) f1 (from BJ/Ks) possible help from f2 (from Bpp with isospin analysis) Hitoshi Murayama TAU2002

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