Could a line betray the mass of Light Dark Matter? C. Boehm, J. - - PowerPoint PPT Presentation

Light Dark Matter to

Could a line

betray the mass of

Light Dark Matter?

• C. Boehm, J. Orloff, P. Salati

Cern, Clermont, Annecy

astro-ph/0607437

• J. Orloff

Light Dark Matter to

Outline

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• Why Dark Matter?

Why not Light DM?

• 511 keV signal from Galactic Center:

Why LDM?

• Cross check: monochromatic line at mdm
• Detectability

• J. Orloff

Light Dark Matter to

Why Dark Matter?

3

• J. Orloff

Light Dark Matter to

Why Dark Matter?

3

Short: (googling Dark Matter 2007) ask Meryl Streep!

• J. Orloff

Light Dark Matter to

Why Dark Matter?

3

f Li ht Dark Matter

Short: (googling Dark Matter 2007) ask Meryl Streep!

• J. Orloff

Light Dark Matter to

Why Dark Matter?

3

f Li ht Dark Matter

Short: (googling Dark Matter 2007) ask Meryl Streep!

• J. Orloff

Light Dark Matter to

Why Dark Matter?

4

• J. Orloff

Light Dark Matter to

Why Dark Matter?

• Need Cold DM with
• n all scales:

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ΩDM = 0.24

• J. Orloff

Light Dark Matter to

Why Dark Matter?

• Need Cold DM with
• n all scales:
• Galaxies’ flat rotation curves

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ΩDM = 0.24

DM halo

• J. Orloff

Light Dark Matter to

Why Dark Matter?

• Need Cold DM with
• n all scales:
• Galaxies’ flat rotation curves
• Clusters’ temp. distributions & collisions

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ΩDM = 0.24

DM halo Cold dark matter X gas

“Bullet” cluster 1E 0657-56

Clowe et al. 2006

lensing

• J. Orloff

Light Dark Matter to

Why Dark Matter?

• Need Cold DM with
• n all scales:
• Galaxies’ flat rotation curves
• Clusters’ temp. distributions & collisions
• Structure formation and CMB

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ΩDM = 0.24

DM halo

Light Dark Matter to

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WMAP astro-ph/0603449

• J. Orloff

Light Dark Matter to

Why Dark Matter?

• Need Cold DM with
• n all scales:
• Galaxies’ flat rotation curves
• Clusters’ temp. distributions & collisions
• Structure formation and CMB
• Nucleosynthesis + CMB:

⇒ DM is non-baryonic

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DM i b

Ωb = 0.04 ≪ ΩDM ΩDM = 0.24

DM halo

Light Dark Matter to

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WMAP astro-ph/0603449

• J. Orloff

Light Dark Matter to

Why Dark Matter?

• Need Cold DM with
• n all scales:
• Galaxies’ flat rotation curves
• Clusters’ temp. distributions & collisions
• Structure formation and CMB
• Nucleosynthesis + CMB:

⇒ DM is non-baryonic

• DM particle: major phenomenological

excuse for physics BSM!

(since DM Direct Detection excl. & oscill.)

⇒ “vanilla” SUSY DM

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DM i b

Ωb = 0.04 ≪ ΩDM ΩDM = 0.24

DM halo

nomenol !

n excl. &

Light Dark Matter to

4

• gical
• scill.)

WMAP astro-ph/0603449

• J. Orloff

Light Dark Matter to

Why Dark Matter?

• Need Cold DM with
• n all scales:
• Galaxies’ flat rotation curves
• Clusters’ temp. distributions & collisions
• Structure formation and CMB
• Nucleosynthesis + CMB:

⇒ DM is non-baryonic

• DM particle: major phenomenological

excuse for physics BSM!

(since DM Direct Detection excl. & oscill.)

⇒ “vanilla” SUSY DM

• Gravity modifications?

Even less conservative! (& contrived)

4

DM i b

Ωb = 0.04 ≪ ΩDM ΩDM = 0.24

DM halo

nomenol !

n excl. &

Light Dark Matter to

4

• gical
• scill.)

WMAP astro-ph/0603449

• J. Orloff

Light Dark Matter to

Why not Light DM?

• Honest poll in this room: “Who would order new MeV particles?”
• More serious: Lee-Weinberg bound ?

Only holds for weak-like cross-sections:

• For other behaviors or GF, relic density can be OK for scalar DM with:
• mdm > 1MeV (otherwise nucleosynthesis problems)
• mdm < 100 MeV (otherwise unseen ’s from 0)
• Involves light gauge boson U, or mirror fermions F, or both

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Ωdm < 1 ⇒ mdm > 2GeV

F dm dm e e

and/or

⇒Intriguing possibility (Boehm, Fayet hep-ph/0305261)

m

σv ∼ C4m−2

F

σannv ∼ m2

dmG2 F (∼1/Ω) U dm dm e e dm e

σv ∼ v2q2

Udmq2 Uem2 dm/m4 U

v 2 v 2

• J. Orloff

Light Dark Matter to

511 keV ‘s from Galactic Center

• 1.6 10-3 photons/cm2/s from the bulge, with energy 511±1 keV
• ⇒ positronium at rest annihilating into 2 photons

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Nothing in the ---- ---- galactic disk!!!

5°= 1kpc = galactic bulge

SPI/INTEGRAL, 2003-2005

10-2 photons/cm2/s/sr 10-4 10-3

• J. Orloff

Light Dark Matter to

Are these e+ “Dark”?

“Found a 0.5 MeV radiation excess? Do your Nuclear Physics right!” However:

• All known potential astrophysical sources (e.g. hypernovae)

more frequent in the disk than in the (quiescent, old stars) bulge.

• Known e+ sources also have known intense gamma lines (unseen)
• Diffuse steady signal requires at least 8(?) steady(?) point sources

On the other hand, the DM density

• must increase in the bulge, and would give a steady, diffuse signal
• fits a reasonable profile: (Ascasibar a-ph/0507142)
• requires both mirror fermions F (e+ signal)

and U boson (relic density too large otherwise) with:

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ρNF W (r) ∼ 1/r σv ∼ C4m−2

F

σv ∼ v2q2

Udmq2 Uem2 dm/m4 U

⎧ ⎨ ⎩ mF > 100GeV mdm ∼ 1 → 100MeV < mU qdmUqeU ∼ 10−6 (for mU ∼ mdm)

• J. Orloff

Light Dark Matter to

Light DM Window

• Upper limits on mdm:
• FSR:

mdm < 20 MeV (Beacom, a-ph/0409403)

• r mdm < 35 MeV w. better cross-section (Boehm, hep-ph/0606058)
• In flight annihilation: some e+ can annihilate before stopping and

exceed

• error bars(???) on continuum mdm < 3MeV (Beacom, a-ph/0512411),
• continuum itself mdm < 20MeV
• Lower limits on mdm:
• Nucleosynthesis disturbed by annihilation mdm > 2MeV

(Serpico, Raffelt, a-ph/0403417)

• Neutrinos from SN1987A too cold (Fayet, Sigl, hep-ph/0602169)

mdm > 10MeV if it couples to neutrinos (not necessary)

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φγ

cont(dm + dm → e+e−γ) > φobs.(.5 → 5MeV )

⇒2MeV < mdm < 20 MeV

• J. Orloff

Light Dark Matter to

The story so far

• There is an intense positronium annihilation line from galactic center
• No easy astrophysical explanation
• ⇒ Imagine annihilation: LDM+LDM e+e-
• Produced positrons radiate energy locally (in 1pc), then (most) find an

e- to form positronium and annihilate (25%) into 511 keV gammas. Requires peculiar particle models, with special ingredient/parameters: what would it take to convince (and believe) this is the real story?

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If DM annihilation produces many e+e- pairs, it must guarantee a minimum number of unambiguous monochromatic ’s ⇒ how much? ⇔ Is there a chance of proving this scenario?

• J. Orloff

Light Dark Matter to

X-check: e+e- production

• For heavy mF>>mdm,e,

heavy F exchange ⇒

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L = ¯ ψF (cRPL + cLPR)ψeφdm + h.c

F dm dm e e c∗

R,L

cL,R

dm dm e e

a+ibγ5 mF

∼ +O(1/m2

F )

Leff = 1 mF φ∗

dmφdm ¯

ψe(a + ibγ5)ψe; a + ib = c∗

LcR.

σ511vr = βe 4πm2

F

• a2β2

e + b2

= 2 10−30 mdm MeV 2 cm3/s

SPI βe =

• 1 − m2

e/m2 dm

reduces to effective interaction

• J. Orloff

Light Dark Matter to

X-check: line at mdm

• 2x3 box diagrams:
• Each superficially but gauge invariance requires 2

external momenta ⇒ and 1/mF expansion OK

• 11

F dm dm e e e c∗

R,L

cL,R dm dm F F e e cL,R c∗

R,L

e dm dm F F F cL,R c∗

R,L

+ +

• d4k/k4

⇒

• mF

d4k/k6 < 1/m2

F

dm dm e e e

a+ibγ5 mF

∼ +O(1/m2

F )

σγγvr = α2 (2π)3 m2

F

m2

e

m2

dm

×

• b2|2C0m2

dm|2 + a2|1 + 2C0(m2 e − m2 dm)|2

C0(q2

1 = 0, (q1 + q2)2 = 4m2 dm, q2 2 = 0, m2 e, m2 e, m2 e)

= d4k iπ2 1 ((k + q1)2 − m2

e) (k2 − m2 e) ((k − q2)2 − m2 e)

= 1 4m2

dm

1 dx x ln(1 − x(1 − x)4m2

dm/m2 e − iεF)

• J. Orloff

Light Dark Matter to

X-check: line /e+e-

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η . = σγγ σ511 = α2 2π2 βe m2

e

m2

dm

a2|1 + 2 (m2

e − m2 dm)C0|2 + b2|2m2 dmC0|2

a2β2

e + b2

Boehm, Orloff, Salati Boehm, Orloff, Salati

102 101 100 101 102 106 104

mdm − me (MeV) η = σγγ/σe+e−

b=0 a=0

• J. Orloff

Light Dark Matter to

X-check: line /e+e-

• Not vanishing guaranteed signal, given the known e+e- signal
• Enhancements?
• ? But dangerous for nucleosynthesis !
• More heavier particles, like tau, in loop?

Not much: (despite prefactor) ⇒ will be relevant only for couplings cL,R scaling like Yukawas

• Kasuya (a-ph/0602296) estimate

( for moduli decay ):

• verestimates by 1000 (!!!) at 10MeV

(wrongly) concludes detectability in near future

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η . = σγγ σ511 = α2 2π2 βe m2

e

m2

dm

a2|1 + 2 (m2

e − m2 dm)C0|2 + b2|2m2 dmC0|2

a2β2

e + b2

η(mτ ≫ mdm) ∼ m2

dm/(m2 F m2 τ)

l f

m2

e/m2 dm

ηK = Γγγ Γe+e− ≈ α2m2

dm

2π2m2

eβ3 e

mdm ≈ me ⇔ βe ≈ 0

~1000

• J. Orloff

Light Dark Matter to

line detectability: now

• SPI sensitivity to narrow lines from point-sources is:

2.5 10-5 photons/cm2/s, in 106 s at 2MeV

• The signal is at most 1000 times smaller: wait 30 years????
• Not much to be gained from angular distribution

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Light

102 101 100 101 102 109 108 107

mdm − me (MeV) φγγ(cm−2s−1)

Boehm, Orloff, Salati

• More sensitive future ideal detector: more background (a-ph/0405441)
• Rejected by energy resolution (not angular)
• J. Orloff

Light Dark Matter to

line detectability: future

15

y gy σ = S √ BG ∼

• S0

1m2 T0 1year 10−3 ΔE/E θ0

• θ2

Ligh

• 102

101 100 101 102 100 101 102

mdm − me (MeV)

Boehm, Orloff, Salati

3σ detection limit

• J. Orloff

Light Dark Matter to

Conclusion

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• J. Orloff

Light Dark Matter to

Conclusion

• Light Dark Matter is an intriguing open possibility, interestingly

supported by 511 keV line from galactic center

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• J. Orloff

Light Dark Matter to

Conclusion

• Light Dark Matter is an intriguing open possibility, interestingly

supported by 511 keV line from galactic center

• Requires deep (anti-unifying) rethinking of usual BSM ideas

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• J. Orloff

Light Dark Matter to

Conclusion

• Light Dark Matter is an intriguing open possibility, interestingly

supported by 511 keV line from galactic center

• Requires deep (anti-unifying) rethinking of usual BSM ideas
• We have computed the minimal monochromatic flux allowing to

unambiguously establish the existence and mass of LDM

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• J. Orloff

Light Dark Matter to

Conclusion

• Light Dark Matter is an intriguing open possibility, interestingly

supported by 511 keV line from galactic center

• Requires deep (anti-unifying) rethinking of usual BSM ideas
• We have computed the minimal monochromatic flux allowing to

unambiguously establish the existence and mass of LDM

• Theorists are not immediately forced to take this possibility

into account (until experimentalists reach the sensitivity/significance mentioned above)

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• J. Orloff

Light Dark Matter to

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• J. Orloff

Light Dark Matter to

Continuum Background

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energy, MeV

• 3

10

• 2

10

• 1

10 1 10

2

10

3

10

4

10

5

10

6

10 MeV

• 1

s

• 1

sr

• 2

. intensity, cm

2

E

• 4

10

• 3

10

• 2

10

• 1

10 1

galdef ID 47_600203a

0.25<l<29.75 , 330.25<l<359.75

• 4.75<b<-0.25 , 0.25<b< 4.75

IC bremss

• total

EB

Strong et al., a-ph/0509290

SPI EGRET COMPTEL RXTE

(330◦ < l < 30◦, |b| < 5◦

Compton Inverse

• J. Orloff

Light Dark Matter to

Underlying Models

Not completely compelling but not impossible:

• N=2 SUSY inspiration: (Fayet ’70 ...ph/0702176)
• Extra U(1) = gauged R-sym (why so light? Sssmall gauge coupling???)
• Mirror fermions needed for anomaly cancellations
• LDM?
• Extra-dimensions:
• Scalar DM = 5th gauge component
• F= KK fermions
• Different moduli story (Takahashi hep-ph/0512296) unifies DE and DM:

Quintessence=Im(S) (pseudo NG boson) scalar DM= Re(S) (other piece of chiral field)

• out-of equilibrium production (also breaks link between relic and 511)
• slowly decays instead of annihilating at rest

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