Transcript ATIC and PAMELA data and its implications

Can dark matter annihilation account
for the cosmic e+- excesses?
Bi Xiao-Jun
IHEP, CAS
2009-11-20
Dark matter, dark energy, matterantimatter asymmetry, Tsinghua
PAMELA results of antiparticles in cosmic rays
Positron fraction
Nature 458, 607 (2009)
Antiproton fraction
Phys.Rev.Lett.102:051101,2009
390 citations after submitted on 28th Oct. 2008, 1paper per day
The total electron+positron spectrum
ATIC bump
Chang et al. Nature456, 362 2008
Fermi excess
Phys.Rev.Lett.102:181101,2009
Possible explanations
Astrophysical sources
Exotic sources
Nearby SNRs, pulsars
Dark matter annihilation
Propagation
Dark matter decay
Early SN stage interaction
of CRs
Possible origins of e+e-: pp interaction (Blasi, 0903.2794)
Occur at the cosmic ray acceleration source: hard spectrum
Comment: nature for Fermi spectrum;
antiprotons may set constraints on this picture
From CRs interaction
(Hu, Bi et al., 0901.1520)
• There is knee in CR spectrum at ~10^15 eV
 
• It is proposed the knee is generated by p  pe e
interaction, with Eγ=1eV, the threshold energy is
at ~10^15 eV
• 3% converted e  e  can explain the ATIC or Fermi
Fermi excess
Nearby
pulsars
Astrophysical sources
D. Hooper et al.
• Nearby pulsars:
S. Profumo
……
• Many possible astrophysical solutions to
explain the excesses are proposed.
However, these sources are easy to
account for the Fermi spectrum, not easy
for ATIC.
Possible explanations
Astrophysical sources
Exotic sources
Nearby SNRs, pulsars
Propagation
Early stage interaction
of CRs
Dark matter annihilation
Dark matter decay
ATIC
Fermi
ATIC
Fermi
??
Primary positron/electrons from dark
matter – implication from new data
• DM annihilation/decay produce leptons mainly
in order not to produce too much antiprotons.
• Very hard electron spectrum -> dark matter
annihilates/decay into leptons.
• Very large annihilation cross section, much
larger (~1000) than the requirement by relic
density.
– 1) nonthermal production,
–
–
–
2) Sommerfeld enhancement
3) Breit-Wigner enhancement
4) dark matter decay.
positron ratio from DM annihilation
Yin, et al.
arXiv:0811.0176
Global fit to the ATIC or Fermi and PAMELA data
Liu, Yuan, Bi, Li, Zhang,
Astro-ph/0906.3858
Possible explanations
Astrophysical sources
Exotic sources
Nearby SNRs, pulsars
Propagation
Early stage interaction
of CRs
Dark matter annihilation
Dark matter decay
ATIC
Fermi
ATIC
Fermi
??
How to have so large flux
• Very large annihilation cross section, much
larger (~1000) than the requirement by relic density.
27
3 1
– 1) nonthermal production,  h 2  3 10 cm s ,suppress gamma

–
–
–
2) Sommerfeld enhancement
3) Breit-Wigner enhancement
4) dark matter decay.
v
Tf
Sommerfeld enhancement
• Kinematically suppression
Mass of φis about 1GeV, is
Kinematically suppressed to antiprotons;
At the same time attractive interaction can
enhance the annihilation rate, Sommerfeld
enhancement. (Arkani-Hamed et al. 0810.0713 )
• For Coulomb potential we have
•
• To enhance the dark matter annihilation we have long
range attractive force
Fine tunning of Sommerfeld
Yuan, Bi, Liu, Yin, Zhang
enhancement and Zhu, Astroph/0905.2736
Astro-ph/0911.0422
J. Zavala, M. Vogelsberger,
and S. White, Astroph/0910.5221
Breit-Wigner enhancement and fine tunning
Bi, He, Yuan,
Astro-ph/0903.0122
We require delta, gamma ~ 10-4 to boost ~1000.
Constraints on the dark matter
annihilation scenario
Since the DM annihilation rate is very large, they
imply the existence of an abundant population of
e+- in the galactic halo, dwarf galaxies, galaxy
clusters, galactic center, or at the early Universe.
The abundance of e+- may induce observables
that can be constrained by the present
experiments.
Constraints from CMB
• DM annihilation
heats and ionizes
the photon-baryon
plasma at z~1000,
constrained by
WMAP and Planck
T.R. Slatyer et al.,
0906.1197
Constraints on the minimal subhalos by
observations of clusters
A. Pinzke et al.,
0905.1948
• Standard CDM predicts the minimal
subhalos
• Observation constrains
• Fermi limit to
• DM is warm
Constraints from extragalactic
diffuse gamma rays
S. Profumo et al.,
0906.0001
Constraint by Galactic diffuse
gamma rays
M. Cirelli et al.,
0904.3830
Emission from the GC
Bi et al., 0905.1253
• Constraint on the central density of DM
• Tension
Exist for the
annihilating
DM scenario,
but consistent
with decay scenarioannihilation
Liu, Yuan, Bi, Li,
Zhang, 0906.3858
decay
Constraints from
the diffuse gamma
ray emission
Zhang, Yuan, Bi,
0908.1236
Possible explanations
Astrophysical sources
Exotic sources
Nearby SNRs, pulsars
Propagation
Early stage interaction
of CRs
Dark matter annihilation
Dark matter decay
ATIC
Fermi
ATIC
Fermi
??
?
Summary
• ATIC
DM
Annihilation: how to boost? Strong constraints!
Decay: how to get such long life time, ~1026s
• Fermi
Astrophysical sources: difficult to test;
(century problems: origin of CRs, knee of CRs