Neutrino masses, dark matter and baryon asymmetry of the universe Takehiko Asaka (Tohoku University) @ The 4 th COE Symposium The 21 st Century Center-of-Excellence Program Sendai International Center, Sendai, 28-30 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/0602150 TA, M. Laine, M. Shaposhnikov, hep-ph/0606209
Cosmology We would like to understand the nature of the universe!
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!
Neutrino oscillations Solar, atmospheric, reactor and accelerator experiments provide Δ 2 3 2 m atm 2 10 ev Δ 2 5 2 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
II. What is the νmsm?
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)
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
Scale of the νmsm T 1 M = ν MD M M M D M = M / M = F Φ / M M 2 2 2 D ν ν 2 Mν = Δm atm 2 5 10 ev Very small Yukawa couplings!
III. Dark matter in the νmsm
Dark matter in the νmsm Unique candidate: the lightest right-handed sterile neutrino Sterile neutrino is not stable particle Main decay: N 3ν τ 5 10 23 10keV 10 5 10 sec 2 M I Θ Barger, Phillips, Sarkar 95 Θ = M / M D I Lifetime can exceed the age of the univ. tu 17 10 sec
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
Allowed region for DM sterile neutrino Allowed Boyarsky et al (astro-ph/0603660)
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 2 3 2 Δ = (8.5 9.5) 10 ev In inverted hierarchy m m atm 2 2 3,2 Δ = (4 6) 10 ev
Masses of active neutrinos The absolute values of active ν masses m O(10 ) e V m, m 6 1 2 3
IV. Baryogenesis in the νmsm
Baryogenesis Baryon asymmetry of the universe n B s = (8.4 8.9) 10 11 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
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 7 2 10 M 17GeV (atm) f I I
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!!
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
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
Baryon asymmetry of the universe 2/3 5 5/3 10 10 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 4 4 2 2 (( ) ) ( ) ( ) 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 11 3 2 2 L12 L13 L23 L23 L23 L23 2 Heavier sterile neutrinos should be degenerate in mass n B s OBS = (8.4 8.9) 10
V. Summary We can solve experimental and observational problems --ν oscillations, dark matter and baryon asymmetry-- in the MSM
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