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Current Issues in Leptogenesis

APCTP, Yonsei, Sep. 15, 2007. Current Issues in Leptogenesis. Eung Jin Chun. Korea Institute of Advanced Study, Seoul. I ssues in leptogenesis. To summarize (not so) new developments in leptogenesis = my two works done in Ann Arbor. Quintessence and leptogenesis

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Current Issues in Leptogenesis

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  1. APCTP, Yonsei, Sep. 15, 2007 Current Issues in Leptogenesis Eung Jin Chun Korea Institute of Advanced Study, Seoul Current Issues in Leptogenesis

  2. Issues in leptogenesis To summarize (not so) new developments in leptogenesis = my two works done in Ann Arbor. • Quintessence and leptogenesis with S. Scopel, arXiv:0706.2375 • Flavor-symmetry for resonant leptogenesis. with K. Turzynski, hep-ph/0703070 Current Issues in Leptogenesis

  3. Introduction • Non-zero neutrino masses and mixing angles provide a convincing evidence of physics beyond the Standard Model. • See-saw mechanism: a paradigm to understand neutrino masses. • The see-saw scenario involves a high-energy scale where lepton number L is not conserved: baryogenesis through leptogenesis. Current Issues in Leptogenesis

  4. W= Seesaw Mechanism Dimension-5 effective operator: added in Standard Model 3 singlet heavy fermions N (RHN) Current Issues in Leptogenesis

  5. k>1 wash-out regime K=/H(T=M) k<1 out-of-equilibrium decay Leptogenesis Fukugita and Yanagida, PLB174, 45 Seesaw mechanism can meet the Sakharov conditions to generate lepton asymmetry from RHN deacy: • L • C and CP • Out-of-equilibrium decay → neutrino mass op. → phases in Y → Γ/H < 1 Hubble constant decay rate SU(2)L sphaleron interactions convert the lepton asymmetry into a baryon asymmetry Current Issues in Leptogenesis

  6. Non-standard cosmology & leptogenesis • Standard scenario: 1) population of RHN due to thermalization -- independent of prehistory. 2) RHN freeze-out during radiation-dominated era. 3) Hierarchical RHN mass. • Non-standard scenario: 1) different origins for populating RHN: non-thermal like from inflaton decay. 2) the Universe before big-bang nucleosynthesis may be dominated by non-radiation energy density. 3) Resonance enhancement of CP/L asymmetry: degenerate RHN mass Current Issues in Leptogenesis

  7. Quintessential Kination and Leptogenesis Current Issues in Leptogenesis

  8. Dark energy & quintessence • ΩDark Energy ~ 0.7 may indicate the existence of a slowly-rolling scalar field,  : Quintessence Caldwell et al., PRL80,1582 • A possibility:  dominance in an earlier stage. Driven by inflation? Chung et al., arXiv:0704.3285 [hep-ph] • A thermal Cold Dark Matter particle decouples earlier and its relic density can be enhanced. Salati., PLB571,121 Current Issues in Leptogenesis

  9. Nb) Dark Energy Kination Cosmological evolution of Quintessence ρα a-3(1+w): equation of state: Current Issues in Leptogenesis

  10. Tracking solution explainingm»DE Steinhardt et al., PRD59,123504 Current Issues in Leptogenesis

  11. Impact on Dark Matter physics During kination the Universe expands faster than during radiation domination a thermal Cold Dark Matter particle decouples earlier and its relic density can be enhanced Salati, PLB571,121 Chung et.al., arXiv:0706.2357 Current Issues in Leptogenesis

  12. Kination Cosmology Define Tr at which Tr is a free parameter with the only bound: Current Issues in Leptogenesis

  13. a-6 ln(ρ) a-4 ar ln(a) Kination Cosmology isoentropic expansion (a3 s=constant): Current Issues in Leptogenesis

  14. T3 T6 ln(ρ) ln(H) T4 T2 Tr Tr ln(T) ln(T) Kination Cosmology time time Current Issues in Leptogenesis

  15. (kination) (radiation) Leptogenesis with Kination A useful parametrization: M≡RHN mass Current Issues in Leptogenesis

  16. Leptogenesis with Kination g*r=10.75 g*(T)=228.75 (SUSY) When zr» M/Tr >>1 with Tr»1 MeV: Thermal leptogenesis can occur at low temperature. Require thermalization of SM particles & RHN: Γgauge ~ α2T > H Require sphaleron interactons in thermal equilibrium: Γsphaleron ~ α4T > H Current Issues in Leptogenesis

  17. Wash-out parameter in Kination Leptogenesis RHN decay rate Effective neutrino mass Wash-out parameter: wide range of possibilities depending on zr, from strong (KÀ 1) to super-weak (K¿ 1) wash-out at fixed effective neutrino mass Current Issues in Leptogenesis

  18. Super-weak wash-out regime When kination dominates, zrÀ 1: 1) Vanishing initial number density of RHN: decay & inverse decay too weak to popularize RHN efficiency of leptogenesis suppressed by 1/K 2) Thermal initial distribution of RHN: maximal efficiency Current Issues in Leptogenesis

  19. Boltzmann equations CP asymmetry in decay: Current Issues in Leptogenesis

  20. Decay & scattering rates decay t-channel scattering s-channel scattering N.B.) scattering is important at high temperature, z<<1 Current Issues in Leptogenesis

  21. Final lepton asymmetry Definition of efficiency: If RHNs thermalize early and decay out-of-equilibrium when they are still relativistic (K<1), we get η=1 With vanishing initial RHN distribution, we get » 1 for K» 1 and ¿ 1 for K¿ 1 or KÀ1. Current Issues in Leptogenesis

  22. ^ vanishing initial RHN density (N(0)=0) Super-weak wash-out regime (K¿1) Semi-analitic solution defining: negligible, main contribution from z<<1 (n=1 radiation, n=2 kination) Scattering dominates. Neglecting scattering: η ~ K2 Current Issues in Leptogenesis

  23. ^ vanishing initial RHN density (N(0)=0) kination radiation Super-weak wash-out regime (K¿1) freeze-out RHN production RHN decay lepton asymmetry produced early Current Issues in Leptogenesis

  24. ^ vanishing initial RHN density (N(0)=0) Strongwash-out regime (KÀ1) Semi-analitic solution Strong inverse-decay ) late decoupling (zfÀ 1) (n=1 radiation, n=2 kination) useful fit: For the decoupling to happen when kination still dominates (zf < zr) Current Issues in Leptogenesis

  25. Strongwash-out regime (KÀ1) integrating BEs using saddle-point technique: n=1 radiation, n=2 kination RHNs decouple late, when scatterings are negligible decouple later for kination Current Issues in Leptogenesis

  26. Strongwash-out regime (KÀ1) kination radiation RHNs thermalize before zf → thermal equilibrium erases any dependence on initial conditions Current Issues in Leptogenesis

  27. Evolution of  for various K Current Issues in Leptogenesis

  28. radiation kination ^ ^ N(0)=0 N(0)=1 Efficiency vs. K Current Issues in Leptogenesis

  29. radiation kination Tr=1 MeV→zr~108 Efficiency vs. zr • smooth transition • from radiation • dominance (zr<1) • to kination • dominance (zr>1). • strong supression • of the efficiency • if zr>>1 • increased efficiency • for 1<zr<100 • if m>0.01 eV Current Issues in Leptogenesis

  30. Quasi-degenerate Neutrinos and Leptogenesis with L – L Current Issues in Leptogenesis

  31. Neutrino mass pattern and non-resonant leptogensis • Efficient leptogenesis: • With Quasi-degenerate neutrinos: • Gravitino problem constrains RHN mass: Requires resonant mechanism Current Issues in Leptogenesis

  32. L-L flavor symmetry Flavon fields and charge assignment: • correction forbidden by Zn : high resonance Fine-tunning: a2/X=bd/Y for m1=m2,3 Automatic maximal atmospheric mixing Current Issues in Leptogenesis

  33. Solar mixing and mass differences Perturbative calculation from corrections with 3,4: correction for 23 for Fine-tunings for smaller solar mass difference: Consistent with large solar mixing Current Issues in Leptogenesis

  34. Fit to Neutrino data Success rate AFM: 10-3 HKV: 10-2 Ours: 10-4 Current Issues in Leptogenesis

  35. Leptogenesis with L-L Baryon asymmetry with degenerate RHNs: CP asymmetry: Current Issues in Leptogenesis

  36. Leptogenesis with L-L Degenerate RHNs ) Radiative generations of N & Re[yyy]23 Current Issues in Leptogenesis

  37. Successful Leptogenesis Final expression for CP asymmetry: y2 dependence 2 suppression ) Current Issues in Leptogenesis

  38. Fit to Leptogenesis Current Issues in Leptogenesis

  39. Life in Ann Arobr Convenient rural life; can be boring Beautiful colors in Autumn Too long winter (6 months…) Fantastic spring/summer Current Issues in Leptogenesis

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