1. E.J.Chun@KIASCurrent Issues in Leptogenesis1 Eung Jin Chun Korea Institute of Advanced Study, Seoul APCTP, Yonsei, Sep. 15, 2007

2. E.J.Chun@KIASCurrent Issues in Leptogenesis2 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

3. E.J.Chun@KIASCurrent Issues in Leptogenesis3 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.

4. E.J.Chun@KIASCurrent Issues in Leptogenesis4 Seesaw Mechanism Dimension-5 effective operator: added in Standard Model 3 singlet heavy fermions N (RHN) W=

5. E.J.Chun@KIASCurrent Issues in Leptogenesis5 Leptogenesis Seesaw mechanism can meet the Sakharov conditions to generate lepton asymmetry from RHN deacy: Fukugita and Yanagida, PLB174, 45 L C and CP Out-of-equilibrium decay → neutrino mass op. → phases in Y → Γ/H < 1 decay rate Hubble constant K=  /H(T=M) k>1 wash-out regime k<1 out-of-equilibrium decay SU(2) L sphaleron interactions convert the lepton asymmetry into a baryon asymmetry

6. E.J.Chun@KIASCurrent Issues in Leptogenesis6 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

7. E.J.Chun@KIASCurrent Issues in Leptogenesis7 Quintessential Kination and Leptogenesis

8. E.J.Chun@KIASCurrent Issues in Leptogenesis8 Dark energy & quintessence Ω Dark 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

9. E.J.Chun@KIASCurrent Issues in Leptogenesis9 equation of state: Nb) Kination Dark Energy Cosmological evolution of Quintessence ρ α a -3(1+w) :

10. E.J.Chun@KIASCurrent Issues in Leptogenesis10 Tracking solution explaining  m »  DE Steinhardt et al., PRD59,123504

11. E.J.Chun@KIASCurrent Issues in Leptogenesis11 Impact on Dark Matter physics Salati, PLB571,121 Chung et.al., arXiv:0706.2357 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

12. E.J.Chun@KIASCurrent Issues in Leptogenesis12 Kination Cosmology T r is a free parameter with the only bound: Define T r at which

13. E.J.Chun@KIASCurrent Issues in Leptogenesis13 Kination Cosmology ln(ρ) ln(a) arar a -4 a -6 isoentropic expansion (a 3 s=constant):

14. E.J.Chun@KIASCurrent Issues in Leptogenesis14 Kination Cosmology ln(H) ln(T) TrTr T2T2 T3T3 ln(ρ) ln(T) TrTr T4T4 T6T6 time

15. E.J.Chun@KIASCurrent Issues in Leptogenesis15 Leptogenesis with Kination A useful parametrization: (kination) (radiation) M≡RHN mass

16. E.J.Chun@KIASCurrent Issues in Leptogenesis16 Leptogenesis with Kination When z r » M/T r >>1 with T r » 1 MeV: g *r =10.75 g * (T)=228.75 (SUSY) Require thermalization of SM particles & RHN: Γ gauge ~ α 2 T > H Γ sphaleron ~ α 4 T > H Require sphaleron interactons in thermal equilibrium: Thermal leptogenesis can occur at low temperature.

17. E.J.Chun@KIASCurrent Issues in Leptogenesis17 Wash-out parameter in Kination Leptogenesis RHN decay rate Wash-out parameter: Effective neutrino mass wide range of possibilities depending on z r, from strong (K À 1) to super-weak (K ¿ 1) wash-out at fixed effective neutrino mass

18. E.J.Chun@KIASCurrent Issues in Leptogenesis18 Super-weak wash-out regime When kination dominates, z r À 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

19. E.J.Chun@KIASCurrent Issues in Leptogenesis19 Boltzmann equations CP asymmetry in decay:

20. E.J.Chun@KIASCurrent Issues in Leptogenesis20 Decay & scattering rates decay s-channel scattering t-channel scattering N.B.) scattering is important at high temperature, z<<1

21. E.J.Chun@KIASCurrent Issues in Leptogenesis21 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 K À 1.

22. E.J.Chun@KIASCurrent Issues in Leptogenesis22 Super-weak wash-out regime (K ¿ 1) vanishing initial RHN density (N(0)=0) ^ Semi-analitic solution defining: (n=1 radiation, n=2 kination) negligible, main contribution from z<<1 Scattering dominates. Neglecting scattering: η ~ K 2

23. E.J.Chun@KIASCurrent Issues in Leptogenesis23 radiation kination Super-weak wash-out regime (K ¿ 1) vanishing initial RHN density (N(0)=0) ^ lepton asymmetry produced early RHN decay freeze-out RHN production

24. E.J.Chun@KIASCurrent Issues in Leptogenesis24 Strong wash-out regime (K À 1) vanishing initial RHN density (N(0)=0) ^ Semi-analitic solution Strong inverse-decay ) late decoupling (z f À 1) (n=1 radiation, n=2 kination) useful fit: For the decoupling to happen when kination still dominates (zf < zr)

25. E.J.Chun@KIASCurrent Issues in Leptogenesis25 Strong wash-out regime (K À 1) integrating BEs using saddle-point technique: n=1 radiation, n=2 kination RHNs decouple late, when scatterings are negligible decouple later for kination

26. E.J.Chun@KIASCurrent Issues in Leptogenesis26 Strong wash-out regime (K À 1) radiation kination RHNs thermalize before z f → thermal equilibrium erases any dependence on initial conditions

27. E.J.Chun@KIASCurrent Issues in Leptogenesis27 Evolution of  for various K

28. E.J.Chun@KIASCurrent Issues in Leptogenesis28 Efficiency vs. K N(0)=0 ^ N(0)=1 ^ kination radiation

29. E.J.Chun@KIASCurrent Issues in Leptogenesis29 Efficiency vs. z r radiation kination T r =1 MeV→z r ~10 8 smooth transition from radiation dominance (z r <1) to kination dominance (z r >1). strong supression of the efficiency if z r >>1 increased efficiency for 1<z r <100 if m>0.01 eV

30. E.J.Chun@KIASCurrent Issues in Leptogenesis30 Quasi-degenerate Neutrinos and Leptogenesis with L  – L 

31. E.J.Chun@KIASCurrent Issues in Leptogenesis31 Neutrino mass pattern and non-resonant leptogensis Efficient leptogenesis: With Quasi-degenerate neutrinos: Gravitino problem constrains RHN mass: Requires resonant mechanism

32. E.J.Chun@KIASCurrent Issues in Leptogenesis32 L  -L  flavor symmetry Automatic maximal atmospheric mixing correction forbidden by Z n : high resonance Fine-tunning: a 2 /X=bd/Y for m 1 =m 2,3 Flavon fields and charge assignment:

33. E.J.Chun@KIASCurrent Issues in Leptogenesis33 Solar mixing and mass differences Perturbative calculation from corrections with 3,4 : Fine-tunings for smaller solar mass difference: Consistent with large solar mixing  for  correction for  23

34. E.J.Chun@KIASCurrent Issues in Leptogenesis34 Fit to Neutrino data Success rate AFM: 10 -3 HKV: 10 -2 Ours: 10 -4

35. E.J.Chun@KIASCurrent Issues in Leptogenesis35 Leptogenesis with L  -L  Baryon asymmetry with degenerate RHNs: CP asymmetry:

36. E.J.Chun@KIASCurrent Issues in Leptogenesis36 Leptogenesis with L  -L  Degenerate RHNs ) Radiative generations of  N & Re[yy y ] 23

37. E.J.Chun@KIASCurrent Issues in Leptogenesis37 Successful Leptogenesis Final expression for CP asymmetry: ) y  2 dependence 2 suppression

38. E.J.Chun@KIASCurrent Issues in Leptogenesis38 Fit to Leptogenesis

39. E.J.Chun@KIASCurrent Issues in Leptogenesis39 Life in Ann Arobr Convenient rural life; can be boring Beautiful colors in Autumn Too long winter (6 months…) Fantastic spring/summer