SuperWIMP Dark Matter Takeo Moroi (Tokyo) 1. Introduction Popular - PowerPoint PPT Presentation

SuperWIMP Dark Matter Takeo Moroi (Tokyo)

1. Introduction Popular candidate of dark matter: thermal relic of a WIMP ⇒ Important alternative: SuperWIMP dark matter [Feng, Rajaraman & Takayama] SuperWIMP: super-weakly interacting massive particle There are many candidates of SuperWIMP • Gravitino, axino, · · · (SUSY) • KK-graviton (UED) • · · ·

Today, I focus on candidates in SUSY model ⇒ Otherwise, too many possibilities... Observable Sector MSSM ~ ~ ~ ( ) ( ) ( ) g B W Axion / axino Graviton / gravitino ~ ~ ~ ~ ~ ( ) ( ) ( ) ( ) ( ) L L E R Q L D R U R ~ ( ) y ν R ν ~ ~ ( ) ( ) H u H d 1 / f PQ 1 / M Pl ⇒ One of the SuperWIMPs may be the LSP

Today’s subject: SuperWIMP dark matter (in SUSY model) • Production processes of SuperWIMP dark matter • Phenomenology Outline 1. Introduction 2. Candidates 3. Production Mechanisms 4. Big-Bang Nucleosynthesis (BBN) Constraints 5. High Energy Cosmic Ray 6. Summary

2. Candidates Gravitino ψ µ : Superpartner of graviton (with spin 3/2) [TM, Murayama & Yamaguchi; Feng, Su & Takayama] i m ˜ g a G aµν + · · · g ¯ ψ α µ J µ √ L ψJ = − α + h . c . ≃ ψσ µν ˜ 2 M Pl 4 6 m 3 / 2 M Pl J µ : Supercurrent M Pl ≃ 2 . 4 × 10 18 GeV : Reduced Planck scale gravitino fermion gravitino gaugino gauge boson sfermion

Axino ˜ a : Superpartner of axion [Goto & Yamaguchi; Bonometto, Gabbiani & Masiero; Chun & Kim; Covi, Kim & Roszkowski] g 2 ∫ 3 d 2 θ AW α W α + h . c . + · · · L int ≃ 32 π 2 f PQ g 2 G aµν + 2¯ µν ˜ 3 aG a g a G aµν ] [ ≃ ˜ aσ µν ˜ + · · · 32 π 2 f PQ A : Axion multiplet f PQ : Peccei-Quin scale Axino mass depends on how the PQ symmetry is broken a ∼ O ( m 3 / 2 ) or m ˜ a ≪ O ( m 3 / 2 ) m ˜

Right-handed sneutrino [Asaka, Ishiwata, TM] • ν R is necessary to generate neutrino masses • Neutrino masses may be Dirac type ⇒ m ˜ ν R ∼ O (100 GeV ) (in gravity mediation) • ˜ ν R can be dark matter if it is the LSP Superpotential (assuming Dirac-type neutrino mass) ν R ˆ l L ˆ W = y ν ˆ H u + W MSSM ⇒ m ν = y ν � H u � Yukawa coupling constants are very small 1 / 2 m 2   y ν sin β = 3 . 0 × 10 − 13 × ν 2 . 8 × 10 − 3 eV 2  

3. Production Mechanisms SuperWIMP can never be thermalized ⇒ How can it be produced in the early universe? One possibility: Scattering and decay of MSSM particles in thermal bath Boltzmann equation (for SuperWIMP X ) dn X dt + 3 Hn X = � σ prod v rel � n 2 MSSM + � Γ prod � n MSSM � σ prod v rel � and � Γ prod � depend on what the SuperWIMP is

If the dominant interaction is dipole-moment type ( dim . = 5 ): ⇒ Production rate is enhanced at higher temperature ⇒ SuperWIMP production occurs mostly at the reheating Reheating temperature to realize gravitino CDM 3 10 ( 10 6 10 GeV ) 1 / 4 g ∗ π 2 M 2 Pl Γ 2 T R ≡ inf 7 10 GeV M (GeV) 1 ⇒ Ω 3 / 2 ∝ T R , m − 1 8 3 / 2 10 GeV 9 10 GeV 2 10 2 3 1 10 10 10 m (GeV) [Kanzaki, Kawasaki, Kohri & Moroi] 3/2

The case of ˜ ν R -LSP: renormalizable interaction ( dim . ≤ 4 ) L int = A ν ˜ L ˜ ν R H u + h . c . + · · · ⇒ Enhanced L-R mixing when A ν is large -12 10 1 m = 100GeV ~ ν R A = a y m ~ ν ν ν ν n / s R ~ ν 10 -14 R n / s 100 2 h 0.1 R R ν ~ ~ ν WMAP Ω -16 4 10 3 Integrand 2 a = 1 ν -18 0.01 10 10 4 10 3 10 2 10 1 100 110 120 130 140 150 Temperature (GeV) m (GeV) ~ ν L ν R production is dominated when T ∼ m ˜ ˜ ν R ⇒ Ω ˜ ν R is insensitive to the thermal history at T ≫ m ˜ ν R

Thermal relic MSSM-LSP decays into SuperWIMP MSSM-LSP: Lightest superparticle in the MSSM sector • MSSM-LSP decays after its freeze-out SuperWIMP = m SuperWIMP Ω ( decay ) Ω (would-be) MSSM-LSP m MSSM-LSP • Ω ( decay ) SuperWIMP depends on MSSM parameters Another possibility: Decay of inflaton (or moduli) • Ω ( inflaton ) SuperWIMP strongly depends on the model of inflation Ω SuperWIMP is model-dependent ⇒ Ω SuperWIMP = Ω CDM is realized in wide parameter space

3. BBN Constraints Lifetime of the MSSM-LSP is usually long ⇒ It may decay after BBN ⇒ Abundances of light elements may be affected BBN constraints depend on • Mass (parent & daughter) • Primordial abundance • Lifetime • Hadronic and electromagnetic branching ratios

BBN constraints on gravitino LSP case Thermal relic density of the MSSM-LSP is assumed Stau MSSM-LSP Bino MSSM-LSP ⇒ Gravitino should be lighter than ∼ 0 . 1 − 10 GeV ⇒ Simple leptogenesis scenario does not work

BBN constraints on ˜ ν R -LSP case (MSSM-LSP = Bino) Ω ( thermal ) and Γ ˜ ν R are both determined by the A -parameter ⇒ L int = A ν ˜ L ˜ ν R H u + h . c . Bino MSSM-LSP ν R = 100 GeV m ˜ m ˜ ν L = 1 . 2 m ˜ B ˜ B → ν L ˜ ν R (+ Z ) [Ishiwata, Kawasaki, Kohri & TM]

4. High Energy Cosmic Ray “PAMELA anomaly” may be due to the decay of CDM ⇔ Of course, other explanations may be possible, though Relevant lifetime for the PAMELA anomaly: ∼ 10 26 sec ⇒ Such a long lifetime can be realized with very small RPV Examples: SuperWIMP decay via R -parity violation (RPV) • Gravitino → W ± l ∓ , Zν, · · · (with L RPV = B RPV ˜ LH u ) ⇒ Important check point: anti-proton flux ν R → l ± l ∓ (with W RPV = λLLE ) • ˜ • · · ·

Gravitino dark matter with bi-linear RPV: L RPV = B RPV ˜ LH u ⇒ Gravitino decays as ψ µ → W ± l ∓ , Zν, · · · GALPROP results (with best-fit model parameters) 10 -3 1 4TeV Positron fraction Anti-proton / proton anti-proton/proton 4TeV 1TeV e - ) e + + Φ 10 -4 0.1 e + / ( Φ 250GeV 1TeV Φ m = 250GeV 3/2 PAMELA 09 PAMELA 10 -5 0.01 10 100 1000 1 10 100 1000 E (GeV) T (GeV) [Ishiwata, Matsumoto & TM] ⇒ m 3 / 2 < ∼ 200 − 300 GeV for the gravitino-LSP case ν R → l ± l ∓ ⇒ No anti-proton constraint for the case with ˜

5. Summary There are well-motivated candidates of SuperWIMPs ⇒ They can be the LSP ⇒ SuperWIMPs are viable candidates of dark matter ⇒ Rich phenomenology is expected with SuperWIMP dark matter SuperWIMP dark matter is an interesting possibility ⇒ You may come up with your own model ⇒ It is dangerous to impose too stringent constraints on properties of the MSSM-LSP