Dark Matter Explanation For e^\pm Excesses In Cosmic Ray

1. Dark Matter Explanation For e^\pm Excesses In Cosmic Ray Xiao-Gang He CHEP, PKU and Physics, NTU

2. The e^\pm Excesses In Cosmic Ray Dark Matter Explanations Particle Physics Model Building Discussions and Conclusions

3. The e^\pm Excesses in Cosmic Ray

5. Atic data

7. Astrophysics for the backgroundThe above results agree well with more complete calculation from GalpropData from PAMELA, ATIC, FERMI and HESS show excesses compared with the above background

9. 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 kinematically.

10. Dark Matter Explanations

11. 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.

14. 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.

16. Dark matter annihilation and Boost factorDM contribution to e^\pm flux

17. An analysis based on CDM N-body simulations shows that the boost factor from clumpy DM distribution can hardly larger.

18. Need to explain the big boost factor: a. Non-thermal DM annihilation: decouple relic density constraint from e^\pm excesses. Just need to fit the Annihilation rate from the latter. 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)

24. c. 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.

27. Features of PAMELA, ATIC and FERMI Data • DM mass serve as cut-off of the range of energy show e^\pm excesses. PAMELA: positron excess in the energy range of 10 to 100 GeV. ATIC up to 650 GeV, Fermi & HESS up to 2 TeV or so. • Excess: needs a factor of 100 to 1000 boost factor compared with usual relic density to explain data. • No anti-proton excess. Dynamic models: Leptophilic couplings or Kinematic models: DM annihilate into some light particle which is not allowed to decay into hadrons due to kinematics. • ATIC: electron/positron excess up to 1 TeV with a sharp falling around 650 GeV. FERMI: excess does not have sharp falling, lower than ATIC, but extended more into higher energies. ATIC and FERMI are in conflict, but PAMELA and ATIC or PAMELA and FERMI can be consistently separately. Which set is correct? An experimental issue!

28. Need to explain the sharp falling at energy around 650 GeV if ATIC is correct! 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. However, if FERMI is correct, then the other way around!

29. Needs to explain why there are excesses in electron and positron, not anti-proton from PAMELA Dynamic model: If dark matter is the source for this, Dark matter must be leptophilic or hadrophobic. Or Kinematic model: DM annihilate into some light particles, lighter than proton + antiproton such that baryon in the final states are suppressed.

30. Particle Physics Model Building

31. A lot of DM models not all of them can explain e^\pm excesses • The simplest model: Darkon model: SM + a real singlet S. S – DM field. Annihilation mediated by s-channel SM Higgs. If Higgs mass is close to 2m_D, Breit-wigner mechanism can produce large boot factor, but too much anti-proton. Needs extension.

32. The most popular model: LSP in MSSM. Neutralino as DM. T-channel LSP annihilation. no mechanism for large boost factor and too much anti-proton. Needs extension. NMSSMhas all needed features. Later.

33. Any model can do the job? Yes, a lot of them too.A) A leptophilic model

37. The PAMELA and ATIC

38. Case c) is out!

39. The PAMELA and FERMI The FERMI data do not have sharp falling at a certain energy, not desirable to have e+e- directly from dark matter annihilation Cases a) and b) are ruled out! Will Case c) work? Yes, but with a higher dark matter mass: 1.5 TeV

40. Case c) works if dark matter mass is around 1.5 TeV! But Cases a) and b) will not work for any dark matter mass

41. B) A light particle decay model

45. Discussions and Conclusions