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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, - PowerPoint PPT Presentation
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Implications of the AMS-02 results on dark matter annihilation and decay
Yu-Feng Zhou
arXiv:1304.1997Collaborators: 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 1
Outline
• A brief introduction to DM • The AMS-02 results • DM interpretations
• DM annihilation• DM decay
• Symmetric DM decay• Asymmetric DM decay
• Conclusions
2
DM revealed from gravitational effects
Gravitational curves
Strong lensing
Weak lensing
Large scale structure
CMB
Bullet clusters
Planck13: DE:68%, DM:27%, Atom:5%arXiv:1303.5062
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.
Searching for WIMPs
space
underground
ground
atmosphere
laboratory
Cosmic-rays: positron fraction
PAMELA, Nature 458, 607 (2009) FERMI
Cosmic-rays: electrons + positrons
ATIC, Nature, 456, 2008,362-365 Fermi-LAT, Phys.Rev.Lett.102:181101,2009
Fermi did not confirm PAMELA excess
Cosmic-rays: electron + positronHESS • No feature below TeV• Spectrum drop off above TeV
Astron.AstronPhys.508,561,2009 [arXiv0905.0105]
Cosmic-ray antiprotons
PAMELA, 0810.4994, 1103.4055,BESS POLAR II, 1107.6000
BESS Polar II extended pbar flux to 0.2 GeVNo excess observed
No excess in antiproton/proton
Antiproton data rule out IVDMH.B.Jin, S.Miao, YFZ, 1207.4408, PRD
AMS-02: e+/(e++e-)
10
PRL, 110, 141102 (2013)
• 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
11Limits 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
Implications
• A rising spectrum of positron fraction, confirming the existence of extra primary positron 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. 16
DM interpretation ?
17
How electrons/positrons travel in the Galaxy
Maurin, etal, astro-ph/0212111
18
Cosmic-ray antiprotons
Diffusion
diffusion convection
reaccelaration
E-loss
source
Reaccelaration
Convection
19
Secondary source (Spalation)
Primary source (SNR)
Electron/positron loss energy due to the magnetic fields, inverse Compton scattering etc..
Sources from DM annihilation/decay
20
DM annihilation, proportional to ρ(x)2
DM halo profile (Einasto)
DM decay, proportional ρ(x), charge symmetric/asymmetric
propagation models
Benchmark models• The conventional model (Model A) Strong, Moskalenko, astro-ph/0101068, • The constrained Model (Model B ) from global Byesian fit to
B/C, 10Be/9 Be, Carbon, Oxegen, etc. Trotta, etal, arXiv:1011.0037
21
Uncertainties and correlations of propagation parameters
Uncertainties in parameters
22
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
Uncertainties in parameters
23
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
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
24
Results for DM annihilation
25
Quality of Fits: 2e,4e highly inconsistent, 2μ, 4μ not good, 2τ, 4τ good
χχ e+e-, spectra too sharp
262e and 4e channels are inconsistent with AMS02 and Fermi-LAT
Results: χχ μ+μ-
27
at 99%C.L.
at 99.99999%C.L.
Fermi
AMS02
Fermi
AMS02
AMS02 inconsistent with Fermi-LAT for 2μ channel
Results: χχ μ+μ-μ+μ-
28
at 99%C.L.
at 99.99999%C.L.
Fermi
AMS02
Fermi
AMS02
AMS02 inconsistent with Fermi-LAT For 4μ channel
Variation of Zh and D0
29Tension between AMS02 and Fermi-LAT Slightly reduce with large Zh=, D0=
Variation of δ2 and γp2
30
The tension between AMS02 and Fermi-LAT remains
Results: χχ τ+τ-
31
at 99%C.L.
at 99.99999%C.L.
Fermi
AMS02
Fermi
AMS02
DM decay:χχ τ+τ-τ+τ-
32
at 99%C.L.
at 99.99999%C.L.
Fermi
AMS02
Fermi
AMS02
Results for DM decay
33
Quality of Fits: DM decay not as good as DM annihilation
Allowed regions
34
Fermi
AMS02 Fermi
AMS02
DM asymmetric decay
35
Source term
For fixed background κ=0.85, δ=0 For varying backgrounds
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.
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