Looking for signals from dark matter annihilation

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Looking for signals from dark matter annihilation

• ???,IHEP(2007/1/4)

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Outline

• Introduction - Dark matter production and
  annihilation
• Status of dark matter detection
• Diffuse gamma excess and its explanation
• Our new result
• Result of positron excess
• conclusion

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Cosmology/astrophysics/particle physics
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H. Baer, A. Belyaev, T. Krupovnickas, J.
OFarrill, JCAP 0408005,2004

• mSUGRA or CMSSM simplest (and most constrained)
  model for supersymmetric dark matter
• R-parity conservation, radiative electroweak
  symmetry breaking
• Free parameters (set at GUT scale) m0, m1/2, tan
  b, A0, sign(m)
• 4 main regions where neutralino fulfills WMAP
  relic density
• bulk region (low m0 and m1/2)
• stau coannihilation region m? ? mstau
• hyperbolic branch/focus point (m0 gtgt m1/2)
• funnel region (mA,H ? 2m?)
• (5th region? h pole region, large mt ?)

However, general MSSM model versions give more
freedom. At least 3 additional parameters m, At,
Ab (and perhaps several more)
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Evidences cluster scale

• Cluster contains hot gas which is at hydro static
  equilibrium. Its temperature follows,
• However, X-ray emission measures the temperature
  and M/Mvisible20

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Evidences cluster scale

• Weak lensing measures the distortion of images of
  background galaxies by the foreground cluster,
  which measures the cluster mass.
• Sunyaev-Zeldovich distortion measures the
  distortion of CMB passing through cluster, which
  measure the temperature of the gas and therefore
  the mass of the cluster.
• other measurements

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Evidences galaxy scale

• From the Keplers law,
  for r much larger than the luminous terms, you
  should have v?r-1/2 However, it is flat or rises
  slightly.

• The most direct evidence of the existence of
  dark matter.

Corbelli Salucci (2000) Bergstrom (2000)
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Evidences cosmological scale

• WMAP measures the anisotropy of CMB, which
  includes all relevant cosmological information. A
  global fit combined with other measurements gives
  (SN, LSS) the cosmological
• paramters precisely.
• ?mh20.135-0.009
• ?m0.27-0.04

Spergel et al 2003
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Non-baryonic DM
From BBN and CMB, it has ?Bh20.02-0.002.
Therefore, most dark matter should be
non-baryonic. ?DMh20.113-0.009
Non-baryonic dark matter dominates the matter
contents of the of the Universe.
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Energy budget of the universe
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Candidates of the cold dark matter

• There are dozens of theoretical models in the
  literature
• Weakly Interacting Massive Particles (WIMPs) as
  thermal relics of Big Bang is a natural candidate
  of CDM-independently proposed by particle
  physics.
• such as neutralinos, KK states, Mirror particles
  

The WIMP miracle for typical gauge couplings and
masses of order the electroweak scale, Wwimph2 ?
0.1 (within factor of 10 or so)
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Thermal history of the WIMP (thermal production)
Thermal equilibrium abundance
At T gtgt m, At T lt m, At T m/22,
,decoupled, relic density is inversely
proportional to the interaction strength
For the weak scale interaction and mass scale
(non-relativistic dark matter particles)
, if
and

WIMP is a natural dark matter candidate giving
correct relic density (proposed trying to solve
hierarchy problem).
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Detection of WIMP

• Indirect detection DM increases in Galaxies,
  annihilation restarts(??2) ID looks for the
  annihilation products of WIMPs, such as the
  neutrinos, gamma rays, positrons at the
  ground/space-based experiments
• Direct detection of WIMP at terrestrial detectors
  via scattering of WIMP of the detector material.

indirect detection
Direct detection
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Status of dark matter search

• Direct detection (null results)

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Indirect detection
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Diffuse gamma rays of the MW

• COS-B and EGRET (20keV30GeV) observed diffuse
  gamma rays, measured its spectra.
• Diffuse emission comes from nucleon-gas
  interaction, electron inverse Compton and
  bremsstrahlung. Different process dominant
  different parts of spectrum, therefore the large
  scale nucleon, electron components can be
  revealed by diffuse gamma.

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Diffuse gamma rays of the MW

• COS-B and EGRET (20keV30GeV) observed diffuse
  gamma rays, measured its spectra.
• Diffuse emission comes from nucleon-gas
  interaction, electron inverse Compton and
  bremsstrahlung. Different process dominant
  different parts of spectrum, therefore the large
  scale nucleon, electron components can be
  revealed by diffuse gamma.

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GeV excess of spectrum

• Based on local spectrum gives consistent gamma in
  30 MeV500 MeV, outside there is excess.
• Harder proton (electron) spectrum explain diffuse
  gamma, however inconsistent with antiproton and
  positron measurements.

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• Hard proton or electron injection index

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Gamma rays by annihilation

• Monoenergetic line
• Continuous spectrum

A smoking gun of DM ann. The flux is suppressed
due to loop production.
Neutralinos in the dark halo can annihilate into
gamma rays and contribute to the diffuse gamma.
The existence of the minihalos will enhance the
flux.
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Contribution from DM
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Fit the spectrum
Enhancement by substructures

• B100
• Fi,j -----?

Adjust the propagation parameters
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Is the dark matter interpretation of the EGRET
gamma excess compatible with antiproton
measurements ?

• Astro-ph/0602632
• Lars Bergstr\"om, Joakim Edsj\"o, Michael
  Gustafsson

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Our result - The SUSY factor

We scan in the SUSY parameter space to find a
suitable spectrum and large flux. The integrated
flux due to different threshold energy. Points
are different SUSY model
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With and without subhalos
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The first generation object

• Diemand, Moore Stadel, 2005
• Depending on the nature of the dark matter for
  neutralino-like dark matter, the first structures
  are mini-halos of 10-6 M?.
• There would be zillions of them surviving and
  making up a sizeable fraction of the dark matter
  halo.
• The dark matter detection schemes may be quite
  different!

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Contributions from different mass ranges of
subhalos
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Calculate cosmic rays

• Adjust the propagation parameters to satisfy all
  the observational data and at the same time
  satisfy the EGRET data after adding the dark
  matter contribution

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Results of different regions
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Our result
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HEAT and positron excess

• HEAT found a positron excess at 8 GeV
• Positron is diffused by GM and lost the
  information of direction.

B100-1000
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Enhancement by subhalos

• The average density (for annihilation) is
  improved with subhalos.
• The corresponding positron flux is improved.

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Result

• The positron fraction can be explained

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Uncertainties in positron flux

• Large uncertainties from propagation
• Uncertainties by the realization of the subhalos
  distribution.

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Conclusion

• The direct/indirect detection of DM is
  complementary to the collider search of DM.
  Multi-messenger approach to final solution of DM
  problem.
• Taking the contribution from DM annihilation into
  account the EGRET data can be explained
  perfectly. (Without DM it is difficult to explain
  the GeV excess even there are large uncertainties
  of cosmic ray propagation).
• EGRET data requires the neutralino mass be in the
  range 4050 GeV and DM distribution be very
  cuspy. Our result is consistent with the
  antiproton flux.
• Existence of subhalos also help to explain the
  positron excess. It also need very cuspy subhalos.

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Problems related with dark matter

• What particle form dark matter?
• Is there one or many spices of dark matter
  particles?
• What are the dark matters quantum numbers?
• How and when was it produced?
• How to explain the observed value of ?
• How is dark matter distributed?
• The role in structure formation How does
  structure form?
• The two sides are closely related The nature
  certainly affect the structure formation, ex.
  hot, cold and warm are different, interacting,
  decaying dark matter have implications in
  structure formation.
• The evidences come from gravitational effects,
  which however shed no light on the nature of DM.
  On the study of effects other than gravity, we
  will show latter that particle physics and
  astrophysics/cosmology are closely related.

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cosmology CMB, LSS, lensing Astrophysics, high
energy gamma, neutrino
Dark matter
Particle physics
Collider physics
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From de Boer
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Neutrinos from the sun or the earth

• Density at the solar center is determined by the
  scattering, insensitive to the local density
• The present data gives
• constraints on the
• parameter space
• IceCube can cover most
• paramter space