Neutrino masses, dark matter and baryon asymmetry of the universe

Transcription

1 Neutrino masses, dark matter and baryon asymmetry of the universe Takehiko Asaka (Tohoku The 4 th COE Symposium The 21 st Century Center-of-Excellence Program Sendai International Center, Sendai, June, 2006 TA, S. Blanchet, M. Shaposhnikov, Phys.Lett.B631 (2005) 151 TA, M. Shaposhnikov, Phys.Lett.B620 (2005) 17 TA, A. Kusenko and M. Shaposhnikov, hep-ph/ TA, M. Laine, M. Shaposhnikov, hep-ph/

2 Cosmology We would like to understand the nature of the universe!

3 Origin of matter in the universe Content of the universe Dark energy Dark matter Baryonic matter Questions: ΩDE 74% ΩDM 22% ΩB 4% What is the dark matter (DM)? How generate the baryon asymmetry of the universe (BAU)? The minimal standard model (MSM) of particle physics cannot answer to these questions!

4 Neutrino oscillations Solar, atmospheric, reactor and accelerator experiments provide Δ m atm 2 10 ev Δ m sol 8 10 ev We must go beyond the MSM!!! A simplest extension including neutrino masses is the νmsm TA, Blanchet, Shaposhnikov 05 TA, Shaposhnikov 05

5 II. What is the νmsm?

6 What is the νmsm? The νmsm = the MSM + three right-handed neutrinos N 1,2,3 Most general renomalizable Lagrangian M L L N i N F L N N N hc 2 μ I c νmsm = MSM + I μγ I αi α IΦ I I +.. Neutrino masses M Dirac = F Φ M Majorana = M 18 new parameters 3 Majorana masses 15 parameters in the neutrino Yukawa matrix (3 Dirac masses, 6 mixing angles, 6 CP phases)

7 In this talk This simple extension can address Neutrino oscillations Dark matter Baryon asymmetry The key point: Majorana masses are smaller than about 100GeV No new energy scale is introduced Seesaw mechanism still works if Dirac masses << Majorana masses

8 Scale of the νmsm T 1 M = ν MD M M M D M = M / M = F Φ / M M D ν ν 2 Mν = Δm atm ev Very small Yukawa couplings!

9 III. Dark matter in the νmsm

10 Dark matter in the νmsm Unique candidate: the lightest right-handed sterile neutrino Sterile neutrino is not stable particle Main decay: N 3ν τ keV sec 2 M I Θ Barger, Phillips, Sarkar 95 Θ = M / M D I Lifetime can exceed the age of the univ. tu sec

11 Constraints on DM sterile neutrino X-ray observations: Radiative decays of DM sterile neutrinos emit the line X-rays Upper bound on mixing! Structure formation: Dolgov Hansen (02)/Abazajian et al (01) Mapelli Ferrara (05)/Abazajian (06) Boyarsky et al (06)/Riemer-Sorensen et (06) Free-streaming effects erase fluctuations on kev TN 1 λfs Mpc M1 T ν Lower bound on mass! )kem 1 >(14 10 VSeljak et al (06)/Viel et al (06) WMAP + Ly-α λ d λ FS

12 Allowed region for DM sterile neutrino Allowed Boyarsky et al (astro-ph/ )

13 Implications of DM sterile neutrino TA, M.Blanchet, M.Shaposhnikov (05)/Boyarsky et al (06) The minimal number of sterile (RH) neutrinos for explaining dark matter and ν oscillations is three Only one sterile neutrino can be dark matter The lightest active neutrino mass should be 6 smaller than O(10 )ev ν 2,3 We can determine the absolute masses of In normal hierarchy 2 2 m3 Δ m atm = (4 6) 10 ev m m sol Δ = ( ) 10 ev In inverted hierarchy m m atm 2 2 3,2 Δ = (4 6) 10 ev

14 Masses of active neutrinos The absolute values of active ν masses m O(10 ) e V m, m

15 IV. Baryogenesis in the νmsm

16 Baryogenesis Baryon asymmetry of the universe n B s = ( ) nb :(B B) number density s: entropy density Primordial inflation sets Δ B = # B # B= 0 Baryogenesis Δ B = # B # B= 0 ΔB 0 Three conditions: Baryon number violation C and CP violation Out of equilibrium Sakharov 67

17 Baryogenesis conditions in the νmsm B and L violations B and L are violated at quantum level EW sphaleron is active for T>T EW ~100GeV L violation in Majorana masses is negligible for T>T EW, C and CP violations 1 CKM phase in quark sector and 6 CP violating phases in lepton sector Out of equilibrium No strong 1st order EW phase transition Sterile neutrinos are not equilibrated for T > T EW M 17GeV (atm) f I I

18 Baryogenesis via neutrino oscillations Akhmedov, Rubakov, Smirnov 98 Idea: Sterile neutrino oscillation is a source of BAU Sterile neutrinos are created and oscillate with CPV The total lepton number is zero but is distributed between active and sterile neutrinos The asymmetry in active (left-handed) neutrinos is transferred partially into baryon asymmetry by sphaleron Point: Not lepton-number generation, but lepton-number separation!!

19 TA, M.Shaposhnikov (05) Generation of asymmetries At F 2, production of sterile neutrinos Φ N Oscillation between N 2 and N 3 L At F 4, generation of ΔLe, μ, τ but Δ L=Δ L +Δ L +Δ L = 0 e μ τ L α L α # L # L α α L F N F L At F 6, generation of ΔL and ΔN, but Δ L+Δ N = 0 L F N F L Δ L=Δ L +Δ L +ΔL e μ τ 0 but Δ L+Δ N = 0 N F L F N Δ N =Δ N1+Δ N2 +ΔN3 0

20 Evolution of asymmetries Active sector ΔN [10 9 ] 2 6 ΔL τ [10 ] Sterile sector ΔN [10 9 ] 3 Δ N=Δ N1+Δ N2 +ΔN3 6 ΔL μ [10 ] Δ 6 L e [10 ] 6 ΔL μ [10 ] ΔN [10 19 ] 1 ΔN [10 9 ] 2 Δ L=Δ L +Δ L +ΔL e μ τ Shaleron converts ΔL partially into baryon asymmetry 28 Δ B= ΔL 0 Kuzmin, Rubakov, Shaposhnikov 79

21 Baryon asymmetry of the universe 2/3 5 5/ M 3 δcp 2 2 Δ 32 / 3 10GeV nb 2 10 s M M 2 2 in NH m3 matm, m2 m sol The effective CP violation parameter (( ) ) ( ) ( ) sinα δcp = 4sR23c R23 sl 12sL13cL13 cl23 + sl23 cl 13 sl 13 sin δl + α2 δcp M + c c s c c s 1 may be possible, M 10GeV 2 3 Δ Δ L12 L13 L23 L23 L23 L23 2 Heavier sterile neutrinos should be degenerate in mass n B s OBS = ( ) 10

22 V. Summary We can solve experimental and observational problems --ν oscillations, dark matter and baryon asymmetry-- in the MSM

23 V. Summary We can solve experimental and observational problems --ν oscillations, dark matter and baryon asymmetry-- in the ν MSM = the MSM + 3 right-handed neutrinos