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The Last Chance for Leptogenesis: Electroweak Baryogenesis

The Last Chance for Leptogenesis: Electroweak Baryogenesis. Hitoshi Murayama What’s  ? Madrid, May 19, 2005. Two Main Questions. Is neutrino mass probe to physics at very high scales, or very low scales? What is the relevance of neutrino mass to the baryon asymmetry to the universe?.

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The Last Chance for Leptogenesis: Electroweak Baryogenesis

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  1. The Last Chance for Leptogenesis:Electroweak Baryogenesis Hitoshi Murayama What’s ? Madrid, May 19, 2005

  2. Two Main Questions • Is neutrino mass probe to physics at very high scales, or very low scales? • What is the relevance of neutrino mass to the baryon asymmetry to the universe?

  3. Outline • Baryogenesis • Looking Up • Looking Down • Conclusions

  4. Baryogenesis

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

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

  7. Baryon AsymmetryCurrent Universe us 1 They basically have all annihilated away except a tiny difference between them

  8. 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?

  9. Electroweak anomaly 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 correspondingly DL=DQ=DQ=DQ=DB=1  D(B–L)=0 Baryon Number Violationin the Standard Model

  10. Baryogenesis in the Standard Model? • Sakharov’s conditions • B violation  EW anomaly • CP violation  KM phase • Non-equilibrium  1st order phase trans. Standard Model may satisfy all 3 conditions! • Electroweak Baryogenesis (Kuzmin, Rubakov, Shaposhnikov) • Two big problems in the Standard Model • First order phase transition requires mH<60GeV • CP violation too small because J det[Yu†Yu, Yd†Yd]~ 10–20<< 10–10

  11. Leptogenesis • You generate Lepton Asymmetry first. • L gets converted to B via EW anomaly • generate L from the direct CP violation in right-handed neutrino decay • Two generations enough for CP violation because of Majorana nature (choose 1 & 3)

  12. Thermal leptogenesis Buchmüller, Plümacher Gravitino Problem • Gravitinos produced in early universe • If decays after the BBN, destroys synthesized light elements • Hadronic decays particularly bad (Kawasaki, Kohri, Moroi)

  13. Looking Up

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

  15. Unique Role of Neutrino Mass • Lowest order effect of physics at short distances • Tiny effect (mn/En)2~(eV/GeV)2=10–18! • Interferometry (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

  16. electromagnetic, weak, and strong forces have very different strengths But their strengths become the same at 1016 GeV if supersymmetry A natural candidate energy scale L~2 1016GeV mn~0.001eV mn~(Dm2atm)1/2~0.05eV mn~(Dm2LMA)1/2~0.009eV  Grand Unification Neutrino mass may be probing unification: Einstein’s dream

  17. SUSY-GUT with seesaw Below MGUT: MSSM + N Above MGUT : GUT + possible flavor physics Leptogenesis from N1 decay Solves the hierarchy problem Provides dark matter Gravitino problem? FCNC? CP? The Orthodoxy

  18. No. Gauge coupling unification is one coincidence GUT doesn’t predict ~MGUT U(1)B-L breaking can be >>MGUT or <<MGUT w/o spoiling GUT It is only a religion right now  Do I believe it?

  19. Can we test seesaw? No 1TeV LC ~ 100 MW 1015GeV LC ~ 1038 MW cf. world power ~ 107 MW

  20. Will I believe it? Possible It will take a lot but conceivable

  21. To believe seesaw • LHC finds SUSY, LC establishes SUSY • no more particles beyond the MSSM at TeV scale • Gaugino masses unify (two more coincidences) • Scalar masses unify for 1st, 2nd generations (two for 10, one for 5*, times two) • Scalar masses unify for the 3rd generation 10 (two more coincidences)  strong hint that there are no additional particles beyond the MSSM below MGUT except for gauge singlets.

  22. Gaugino masses test unification itself independent of intermediate scales and extra complete SU(5) multiplets Scalar masses test beta functions at all scales, depend on the particle content Gaugino and scalars (Kawamura, HM, Yamaguchi)

  23. To believe seesaw (cont.) • The neutralino mass and its coupling to other SUSY particles are measured • Calculate the neutralino annihilation cross section, agrees with the Mh2=0.14 • Calculate the neutralino scattering cross section, agrees with the direct detection • B-mode fluctuation in CMB is detected, with a reasonable inflationary scale  strong hint that the cosmology has been ‘normal’ since inflation (no extra D etc)

  24. Annihilation cross section B-mode fluctuation “Normal” cosmology

  25. To believe seesaw (cont.) • 0 seen, neutrinos are Majorana • LBL oscillation finds 13 soon just below the CHOOZ limit • determines the normal hierarchy and finds CP violation • Scalar masses unify for the 3rd generation 5* up to the neutrino Yukawa coupling y3~1 above M3=y32v2/m3 neutrino parameters consistent with leptogenesis

  26. To believe seesaw (cont.) Possible additional evidence, e.g.,: • lepton-flavor violation (e conversion, ) seen at the “reasonable” level expected in SUSY seesaw (even though I don’t believe mSUGRA) • BdKS shows deviation from the SM consistent with large bR-sR mixing above MGUT • Isocurvature fluctuation seen suggestive of N1 coherent oscillation, avoiding the gravitino problem

  27. Large mixing between nt and nm Make it SU(5) GUT Then a large mixing between sR and bR Mixing among right-handed fields drop out from CKM matrix But mixing among superpartners physical O(1) effects on bs transition possible (Chang, Masiero, HM) Expect CP violation in neutrino sector especially if leptogenesis Large q23 and quarks

  28. CP violation in Bs mixing (BsJ/yf) Addt’l CP violation in penguin bs (BdfKs) Consequences in B physics Indirect evidence for lepton-quark unification

  29. If all of the above happens I’ll probably believe it. It’s conceivable.

  30. Looking Down

  31. LHC may find different directions • Suppose LHC will find TeV-scale extra dimensions, Randall-Sundrum, etc • Cosmology goes haywire above TeV • Need to look for the origin of small neutrino mass, baryon asymmetry at low energies • Even with SUSY, gravitino problem may force us this way

  32. Late neutrino mass • Seesaw formula: m=v2/<<v because v <<  • Another way to get small mass with O(1) coupling: m =v(<>/n (Dirac) m =v2(<>n/n+1 (Majorana) Even if  ~TeV, <><<v works. • “Late” neutrino mass because <><<v implies a late time phase transition • e.g., n=2,  ~TeV  <>~MeV

  33. Explicit Realization _ U(1)l: l(+1), (-1), L(0), L(0), N(0) Recall “anarchy”: no hierarchy, large mixing All Yukawa couplings here are ~O(1) Can be “gauged” for the non-anomalous Z3 subgroup

  34. Viable • Remarkably, phenomenological constraint weak despite the low scale • For m>1MeV,  above BBN, OK • SN1987A limit OK because  couples with strength m • If gauged, the domain walls are becoming important only now, possible imprint on CMB anisotropy (Checko, Hall, Okui, Oliver) (Davoudiasl, Kitano, Kribs, HM)

  35. Electroweak Baryogenesis • Even with two generations, CP is violated J=Im Tr(YY†MN*Y*YTMNMN*MN) • Reflection asymmetry ~ J/MN4 =Im Tr(YY†MN*Y*YTMNMN*MN)/MN4 ~O(1) Hall, HM, Perez

  36. Electroweak Baryogenesis • L decays quickly as Ll, • l asymmetry converted to baryon asymmetry by sphaleron with rate ~ 20W5 ~ 10-7

  37. Last chance for leptogenesis: electroweak scale Can generate enough asymmetry thanks to anarchy of neutrinos Vector-like L+L induce LFV, tends to be big! In principle, all degrees of freedom can be produced at accelerators, possibly CP phase measured at ILC: fully testable Electroweak Baryogenesis _

  38. Electroweak Baryogenesis • Need 1st order phase transition • Low-cutoff theory allows for higher dimension operator such as V~|H|6/2 • Can cause 1st order phase transition without a too-light Higgs (Grojean, Servant, Wells) • No gravitino problem, needs normal cosmology only below TeV.

  39. Conclusion

  40. Conclusions • electroweak baryogenesis not possible in the SM • leptogenesis works, but gravitino problems • Neutrino mass may look up • Seesaw not directly testable, but it is conceivable that we get convinced • Neutrino mass may look down • Late time neutrino mass fully testable in principle, interesting alternative • Even offers the opportunity for the low-scale leptogenesis at electroweak phase transition

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