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...

νR

y

ν

QL

( )

~

( )

~ DR

( )

~ UR

( )

~ E R

( )

~ L L

( )

~ Hu

( )

~ Hd

( )

~ W

( )

~ g

( )

~ B

( )

~

MSSM Graviton / gravitino Axion / axino 1 / f PQ Observable Sector 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 ψµ: Superpartner of graviton (with spin 3/2)

[TM, Murayama & Yamaguchi; Feng, Su & Takayama]

LψJ = − i 2MPl ψα

µJµ α + h.c. ≃

m˜

g

4 √ 6m3/2MPl ¯ ψσµν˜ gaGaµν + · · · Jµ: Supercurrent MPl ≃ 2.4 × 1018 GeV: Reduced Planck scale

gravitino fermion sfermion gravitino gaugino gauge boson

Axino ˜

a: Superpartner of axion

[Goto & Yamaguchi; Bonometto, Gabbiani & Masiero; Chun & Kim; Covi, Kim & Roszkowski]

Lint ≃ g2

3

32π2fPQ

∫

d2θAWαWα + h.c. + · · · ≃ g2

3

32π2fPQ

[

aGa

µν ˜

Gaµν + 2¯ ˜ aσµν˜ gaGaµν] + · · · A: Axion multiplet fPQ: Peccei-Quin scale

Axino mass depends on how the PQ symmetry is broken

m˜

a ∼ O(m3/2) or m˜ a ≪ O(m3/2)

Right-handed sneutrino

[Asaka, Ishiwata, TM]

• νR is necessary to generate neutrino masses
• Neutrino masses may be Dirac type

⇒ m˜

νR ∼ O(100 GeV) (in gravity mediation)

• ˜

νR can be dark matter if it is the LSP

Superpotential (assuming Dirac-type neutrino mass)

W = yνˆ νRˆ lL ˆ Hu + WMSSM ⇒ mν = yνHu

Yukawa coupling constants are very small

yν sin β = 3.0 × 10−13 ×

 

m2

ν

2.8 × 10−3 eV2

  1/2

• 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)

dnX dt + 3HnX = σprodvreln2

MSSM + ΓprodnMSSM

σprodvrel and Γprod 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

10 1

2

10

3

10

2

10

3

10 m (GeV)

3/2

M (GeV)

1

7

10 GeV

8

10 GeV

6

10 GeV

9

10 GeV

[Kanzaki, Kawasaki, Kohri & Moroi]

TR ≡

( 10

g∗π2M 2

PlΓ2 inf )1/4

⇒ Ω3/2 ∝ TR, m−1

3/2

The case of ˜

νR-LSP: renormalizable interaction (dim. ≤ 4) Lint = Aν ˜ L˜ νRHu + h.c. + · · · ⇒ Enhanced L-R mixing when Aν is large

100 110 120 130 140 150 0.01 0.1 1 m (GeV)

R

ν ~

Ω h

L

ν ~

100 2

4 3 2 a = 1 ν WMAP 10

• 12

10-14 10

• 16

10

• 18

10 3 10 2 10 1 10 4

n / s

R

ν

~

Integrand n / s

R

ν

~

Temperature (GeV) m = 100GeV

R

ν ~

A = a y m

ν ν ν

R

ν ~

˜ νR production is dominated when T ∼ m˜

νR

⇒ Ω˜

νR is insensitive to the thermal history at T ≫ m˜ νR

Thermal relic MSSM-LSP decays into SuperWIMP MSSM-LSP: Lightest superparticle in the MSSM sector

• MSSM-LSP decays after its freeze-out

Ω(decay)

SuperWIMP = mSuperWIMP

mMSSM-LSP Ω(would-be)

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

ΩSuperWIMP is model-dependent ⇒ ΩSuperWIMP = ΩCDM 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

Bino MSSM-LSP Stau MSSM-LSP

⇒ Gravitino should be lighter than ∼ 0.1 − 10 GeV ⇒ Simple leptogenesis scenario does not work

BBN constraints on ˜

νR-LSP case (MSSM-LSP = Bino) Ω(thermal) and Γ˜

νR are both determined by the A-parameter

⇒ Lint = Aν ˜ L˜ νRHu + h.c.

Bino MSSM-LSP

[Ishiwata, Kawasaki, Kohri & TM]

m˜

νR = 100 GeV

m˜

νL = 1.2m ˜ B

˜ B → νL˜ νR(+Z)

• 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: ∼ 1026 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 LRPV = BRPV ˜

LHu) ⇒ Important check point: anti-proton flux

• ˜

νR → l±l∓ (with WRPV = λLLE)

• · · ·

Gravitino dark matter with bi-linear RPV: LRPV = BRPV ˜

LHu ⇒ Gravitino decays as ψµ → W ±l∓, Zν, · · ·

0.01 0.1 1 10 100 1000 Φ

e+ / (Φ e+ + Φ e-)

E (GeV)

GALPROP results (with best-fit model parameters)

10-5 10-4 10-3 1 10 100 1000 anti-proton/proton T (GeV)

Positron fraction Anti-proton / proton m = 250GeV 1TeV 4TeV 250GeV 1TeV 4TeV

3/2

PAMELA PAMELA 09

[Ishiwata, Matsumoto & TM]

⇒ m3/2 < ∼ 200 − 300 GeV for the gravitino-LSP case ⇒ No anti-proton constraint for the case with ˜ νR → l±l∓

• 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