Cosmological matter-antimatter asymmetry & possible CP violation in neutrino oscillations

1. Cosmological matter-antimatter asymmetry &possible CP violation in neutrino oscillations Zhi-zhong Xing (IHEP) International UHE Tau Neutrino Workshop 23 – 26 April 2006, IHEP, Beijing

2. Outline Motivation RGE Telescope minimal Seesaw Model

3. Motivation

4. New Physics • Dark matter • Dark energy • Cosmic inflation • Solar neutrino oscillations • Atmospheric neutrino oscillations • Cosmological matter-antimatter asymmetry 3-year WMAP Observations astro-ph/0603449 astro-ph/0603450 astro-ph/0603451 astro-ph/0603452

5. Can 1 Stone Kill 3 Birds? Cosmological matter-antimatter asymmetry (observational evidence) Dark matter Connection ? Big Bang Inflation Dark energy Atmospheric and solar neutrino oscillations (experimental evidence) 前苏联氢弹之父

6. Yes or No Yes, if SM + Right-handed neutrinosN •-masses: Yukawa interactions • Small -masses: Seesaw mechanism • Flavor mixing: MNS matrix (3 CPV phases) • Macro-CPV: Out-of-equilibrium N-decays • B-violation: L-violation (sphaleron process) • Baryogenesis: Leptogenesis mechanism

7. Leptogenesis m m m M M M 3 2 1 14 2 2 1 3 10 GeV 10 GeV Quantum correction Seesaw -oscillations ()_0 decay Question:Are the CP-violating phases at low- and high-energy scales correlated?

8. RGE Telescope

9. RGEs = Cable Car The New Physics Scale The Electroweak Scale Radiative Corrections An easy way to imagineradiative corrections If you feelsickin the cable carfromthe topdown tothe bottom, you have got significantradiative corrections.

10. Quark mixing (CKM): θ12 ～13°→ θ23 ～2°→ θ13 ～0.2°→ δ～65° Lepton mixing (MNS): θ23 ～45°→ θ12 ～33°→ θ13<10°→ δ/ρ/σ Flavor Mixing and CP Violation

11. One-loop renormalization group equation of (with diagonal): RGEs of Neutrino Masses Below the seesaw scale (MSSM) After SSB at the electroweak scale

12. RGEs of Mixing Angles Of 3 angles, is most sensitive to RGE effects

13. RGEs of CP-violating Phases (I) The RGE evolution of the Dirac phase depends on and : If and were vanishing, the leading terms would vanish; The radiative generation of is possible. (Luo, Mei, Xing05).

14. RGEs of CP-violating Phases (II) The RGE evolution of Majorana phases and depends on :

15. Numerical Examples (1-I) We concentrate on the case that 3 neutrino masses are nearly degenerate and. (Luo, Mei, Xing2005) Seesaw scale Electroweak scale

16. Numerical Examples (1-II)

17. Neutrinoless double-beta decay: Allowed! Numerical Examples (2)

18. Simultaneous generation of appreciable and from , no problem; and from , no problem. But and from , suppressed Numerical Examples (3)

19. The Dirac phase can be radiatively generated from one or two Majorana phases; even is achievable. The radiative generation of either Majorana phase or is okay, but difficult to simultaneously generate both of them. RGE Running of CPV Phases Three CP-violating phases are entangled with one another in the one-loop RGE evolution. The parameters of Majorana neutrinos run faster than those of Dirac neutrino in most cases (Xing, Zhang06) Helpful for model building, to establish a kind of connection between the phenomena of CP violation at high and low scales. But a specific relation between leptogenesis and CP violation in neutrino oscillations is strongly model-dependent.

20. minimal Seesaw Model

21. The minimal seesaw model (MSM): 2Right-handed neutrinos added to MSSM • Principle of minimal particle content • SU(2)U(1) gauge symmetry preserved • Lepton number violating MRintegrated out, leading to a dimension-5 operator with an effective coupling matrix: Seesaw relation The Minimal Seesaw Model

22. Leptogenesis in the MSM An incomplete list of recent works on the MSM and leptogenesis •Frampton, Glashow, Yanagidahep-ph/0208157(PLB) •Endoh et alhep-ph/0209020(PRL) •Raidal, Strumiahep-ph/0210021(PLB) •Rabyhep-ph/0302027(PLB) •Dutta, Mohapatrahep-ph/0305059(PRD) •Barger, Dicus, He, Lihep-ph/0310278(PLB) •Guo, Xinghep-ph/0310326(PLB) •Ibarra, Rosshep-ph/0312138(PLB) •Mei, Xinghep-ph/0312167(PRD) •Turzynskihep-ph/0401219(PLB) •Chang, Kang, Siyeonhep-ph/0404187(PLB) CPV phase entanglement Radiative corrections

23. SmirnovPlot • Normal -mass hierarchy: • Inverted -mass hierarchy:: Neutrino Masses in the MSM There is a massless neutrino eigenstate! is of rank2, henceDet()=0holds, or

24. •The seesaw models with a single right-handed neutrino ruledout (ifof rank1,2massless -eigenstates, no CP violation). One-loop RGE: Some Comments Some comments on the features of MSM: •The2N-seesaw models may serve as an approximation of the3N-seesaw models withN3decoupled in the limit ofM3 » M1,2. •The texture ofis essentially stable against RGE effects fromM1toMZ. So isDet()=0 or m1 =0orm3 =0.

25. RGE-running Functions Results(Mei, Xing04): Det()keepsvanishing atMZ 6parameters ofYatMZ

26. A typical example: Frampton-Glashow-Yanagida ansatz (02) FGY Ansatz in the MSM Flavor structure: texture zeros? The seesaw mechanism itself is not quantitatively predictive, unless a specific lepton flavor structure is assumed. A combination of the seesaw mechanism and a certain flavor symmetry or a few texture zeros, whose empirical role is to reduce the number of free parameters, is therefore needed.

27. at low scale CP-violating Phases It turns out that two CP-violating phases are calculable! (Guo, Xing04) Due tom1=0, thephase can be rotated away.

28. One-zero textures selected by data(Xing04): Pattern Condition   or   or     or    

29. Interference leads to CPV If the interactions of N1 are in thermal equilibrium when N2 decays, can be erased before N1 decays. Then only , produced by the out-of-equilibrium decay of N1 , can survive. Leptogenesis in the MSM Leptogenesis at the seesaw scale (Fukugita, Yanagida86) Lepton-number-violating and CP-violating decays:

30. If the RGE effect were neglected, one would obtain: Independent ofM2! (Guo, Xing04) In both cases,is directlyrelated to. will vanishif vanishes, or vice versa. Then the RGE-corrected result is (Mei, Xing04) Leptogenesis in the MSM Quantities atM1are expressed by those atMZ. Direct link betweenhighandlowscale CP-violating phenomena!

31. The above lepton number asymmetry is eventually converted into a net baryon number asymmetry via the non-perturbative sphaleron process(Kuzmin, Rubakov, Shaposhnikov85): Leptogenesis in the MSM Cosmological baryon asymmetry: Lepton number asymmetry from: If the effective neutrino mass parameter lies in the range , then dilution factordwill approximately readas follows:

32. Numerical Illustration YB YB θ13(MZ) θ13(MZ)

33. •M1 must be heavy enough (). And a conflict between achieving the successful thermal leptogenesis and avoiding the over-production of gravitinos ( ) exists in MSSM. •Distinguishing between the SM and MSSM results needs other experimental information (for example, those MSSM-motivated LFV processes etc.) •Distinguishing between and is possible at low energy scales, as they belong separately to normal and inverted neutrino mass hierarchies. Leptogenesis in the MSM Some comments: Concluding remark: Leptonic CP violation to be observed might be one of the key reasons for the observed matter-antimatter asymmetry of our universe—fundamentally important

34. so we are here today something occurred over there one billion years ago L  B

35. Thank You