Leptophilic Dark Matter from ATIC and Pamela

1. Leptophilic Dark Matter from ATIC and Pamela Xiao-Gang He National Taiwan University In Collaboration with Xiao-Jun Bi arXiv: 0903.0122

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. 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 D D N N gNNH • 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.

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