Implications of the AMS-02 results on dark matter annihilation and decay

1. Implications of the AMS-02 results on dark matter annihilation and decay Yu-Feng Zhou arXiv:1304.1997 Collaborators: Hong-Bo Jin and Yue-Liang Wu State Key Lab for Theoretical Physics, Kavli Institute for Theoretical Physics China, Institute of Theoretical Physics, Chinese Academy of Sciences

2. Outline • A brief introduction to DM • The AMS-02 results • DM interpretations • DM annihilation • DM decay • Symmetric DM decay • Asymmetric DM decay • Conclusions

3. DM revealed from gravitational effects Gravitational curves Large scale structure Bullet clusters Strong lensing CMB Planck13: DE:68%, DM:27%, Atom:5% arXiv:1303.5062 Weak lensing

4. Weakly interacting massive particles (WIMPs) Weakly Interacting Massive Particles (WIMPs) • Particle physics independently predicts WIMPs • WIMPs have just the right thermal relic density • WIMPs are testable by the current exp.

5. Searching for WIMPs space atmosphere ground underground laboratory

6. Cosmic-rays: positron fraction FERMI PAMELA, Nature 458, 607 (2009)

7. Cosmic-rays: electrons + positrons Fermi-LAT, Phys.Rev.Lett.102:181101,2009 ATIC, Nature, 456, 2008,362-365 Fermi did not confirm PAMELA excess

8. Cosmic-rays: electron + positron • HESS • No feature below TeV • Spectrum drop off above TeV Astron.AstronPhys.508,561,2009 [arXiv0905.0105]

9. Cosmic-ray antiprotons Antiproton data rule out IVDM H.B.Jin, S.Miao, YFZ, 1207.4408, PRD No excess in antiproton/proton BESS Polar II extended pbar flux to 0.2 GeV No excess observed PAMELA, 0810.4994, 1103.4055,BESS POLAR II, 1107.6000

10. AMS-02: e+/(e++e-) • Positron fraction measured from 0.5 to 350 GeV • In total 6.8x106 positron and electron events presented • Positron spectrum is steadily increasing from 10 to ~250 GeV • The slope decreases by an order of magnitude from 20 to ~250 GeV PRL, 110, 141102 (2013)

11. Limits on the amplitude of a dipole anisotropy <0.03 at 95% C.L

12. Positron spectrum up to 350 GeV

13. Electron spectrum from 1 GeV – 500 GeV

14. All electron from 0.5 GeV – 700 GeV

15. AMS-02 did not confirm the substructures observed by PAMELA

16. Implications • A rising spectrum of positron fraction, confirming the existence of extra primarypositron sources. • The excess is isotropic, consistent with DM origin, but so far cannot rule out contributions from nearby pulsars. • The slope of the spectrum decreases by an order or magnitude from ~20-250 GeV, disfavor heavy DM around TeV scale • Unprecedented precision due to high statistics, useful in distinguishing DM models.

17. DM interpretation ?

18. How electrons/positrons travel in the Galaxy Maurin, etal, astro-ph/0212111

19. Cosmic-ray antiprotons diffusion convection E-loss reaccelaration source Diffusion Primary source (SNR) Convection Secondary source (Spalation) Reaccelaration Electron/positron loss energy due to the magnetic fields, inverse Compton scattering etc..

20. Sources from DM annihilation/decay DM annihilation, proportional to ρ(x)2 DM decay, proportional ρ(x), charge symmetric/asymmetric DM halo profile (Einasto)

21. propagation models Benchmark models • The conventional model (Model A) Strong, Moskalenko, astro-ph/0101068, • The constrained Model (Model B ) from global Byesianfit to B/C, 10Be/9 Be, Carbon, Oxegen, etc. Trotta, etal, arXiv:1011.0037 Uncertainties and correlations of propagation parameters

22. Uncertainties in parameters Modifications of Model B with variations in • C1(C2):Diffusion halo height Zh and diffusion coefficient D0 • D1(D2)Power index δ2 • E1(E2) Power index primary proton γp2

23. Uncertainties in parameters Instead of varying the power index primary electron γe2, the normalization and slope of primary electron flux are set free. At high energies The cross section and k are nearly degenerate in positron fraction

24. Data selection • Data included ( energy >20 GeV, to avoid solar modulation) • PAMELA positron fraction ( 4 data points) • Fermi-LAT positron fraction (10 data points) • AMS02 positron fraction (31 data points) • Fermi-LAT electron+positron (28 data points) • PAMELA electron (18 data points) • AMS02 electron (35 data points) • Energy resolution of each exp. taken into account • PAMELA: 5% • Fermi-LAT: 6% at 7GeV, 15% at 1TeV • AMS02: 1.4% at 100 GeV and above

25. Results for DM annihilation Quality of Fits: 2e,4e highly inconsistent, 2μ,4μ not good, 2τ,4τ good

26. χχe+e-, spectra too sharp 2e and 4e channels are inconsistent with AMS02 and Fermi-LAT

27. Results: χχμ+μ- Fermi AMS02 at 99%C.L. Fermi AMS02 AMS02 inconsistent with Fermi-LAT for 2μ channel at 99.99999%C.L.

28. Results: χχμ+μ-μ+μ- Fermi AMS02 at 99%C.L. Fermi AMS02 AMS02 inconsistent with Fermi-LAT For 4μ channel at 99.99999%C.L.

29. Variation of Zh and D0 Tension between AMS02 and Fermi-LAT Slightly reduce with large Zh=, D0=

30. Variation of δ2 and γp2 The tension between AMS02 and Fermi-LAT remains

31. Results: χχτ+τ- Fermi AMS02 at 99%C.L. Fermi AMS02 at 99.99999%C.L.

32. DM decay:χχτ+τ-τ+τ- Fermi AMS02 at 99%C.L. Fermi AMS02 at 99.99999%C.L.

33. Results for DM decay Quality of Fits: DM decay not as good as DM annihilation

34. Allowed regions AMS02 Fermi AMS02 Fermi

35. DM asymmetric decay Source term For fixed background κ=0.85, δ=0 For varying backgrounds

36. Conclusions • The precision AMS-02 data provide us rich information. Different DM models can de distinguished • DM annihilation into 2μ, 4μ which were favored by the PAMELA and Fermi-LAT, is not favored by the AMS-02 data. The conclusion is robust against the variation of propagation modes and the normalization of electron backgrounds. • More consistent fits obtained for 2τ, 4τ channels • AMS-02 data favor DM annihilation over DM decay. • Asymmetric DM decay can slightly favored over the symmetric case.