1. Leptophilic Dark Matter from ATIC and Pamela
Xiao-Gang He
National Taiwan University
In Collaboration with Xiao-Jun Bi
arXiv:

2. Evidences for Dark Matter
The ATIC and PAMELA Data
A Model for Leptophilic Dark Matter
Discussions and Conclusions

3. Evidences for Dark Matter

4. Dark Matter Quest Energy density budget of Universe from PDG,
Introduction
Dark Matter Quest
Energy density budget of Universe from PDG,
Baryon: 4.25 %
Dark energy: 73(3) %
Dark matter: 20 %
and small portion of Others.
Many weakly interacting massive particle (WIMP) models are proposed ...
But dark matter identity and property are still not known.

5. Big-Bang Nucleosynthesis

6. WMAP Results on CMB (2003)

8. Rotation velocity v->Sqrt[1/r] away from optical disc if there is nothing between. But observation show differently.

9. Gravitational lensing

10. Non-Interacting Dark Matter?

12. DM Direct Search
The current and projected experimental upper limits of spin-independent WIMP-nucleon elastic cross-section as a function of WIMP mass are shown in the right figure.
The effective darkon-higgs coupling is needed for elastic darkon-nucleon cross section calculation. D N
gNNH

14. ATIC and PAMELA Data

16. Atic data

17. Features of ATIC and PAMELA Data
PAMELA: positron excess in the energy range of 10 to 100 GeV.
Excess: needs a factor of 100 to 1000 boost factor
compared with usual relic density to explain data.
No anti-proton excess. If excess is due to dark matter, then it is leptophilic (or hadrophobic) or it is light and is not allowed to decay or annihilate into hadrons kinematically.
ATIC: electron/positron excess up to 1 TeV with a sharp falling around 650 GeV.

18. Origin of e^+/e^- excess?
Nearby mature pulsars. In order to contribute
significantly, a pulsar cannot be either too young
nor too old.
b. Dark matter annihilation:
c. Dark matter decay
No anti-proton excess. If excess is due to dark
matter, then it is leptophilic (or hadrophobic) or it
is light and is not allowed to decay or annihilate into
hadrons kinematicaly.

19. Need to explain the big boost factor:
a. An analysis based on CDM N-body simulations
shows that the boost factor from clumpy DM distribution
can hardly larger.
b. Sommerfeld effect. For on-relativistic scattering,
there is an enhancement factor R. Requiering light
mediating particle. For massless particle,
R = a pi/v/(1-e^{- a pi/v}) (a = coupling^2/4 pi)
c. Non-thermal relic dark matter
d. Dark matter decay

20. e. Breit-Wigner enhancement mechanism Annihilation rate:
v^2 depend on thermal average, if delta and gamma
small enough, annihilation rate sensitive on T, different
thermal relic density than non-resonant case, and
can produce large boost factor.

21. Need to explain the sharp falling at energy around 650 GeV
If annihilation, dark matter needs to
annihilate into e^+ e^-
If to mu and tau pairs, secondary e^- and
e^+, does not have the sharp falling feature.

22. Needs to explain why there are excesses in electron and positron, not anti-proton
If dark matter is the source for this, Dark
matter must be leptophilic or hadrophobic.

23. A Model for Leptophilic Dark Matter

34. Discussions and Conclusions