Can dark matter annihilation account for the cosmic e+- excesses? Bi Xiao-Jun IHEP, CAS 2009-11-20 Dark matter, dark energy, matter-antimatter asymmetry, Tsinghua University, Taiwan

PAMELA results of antiparticles in cosmic rays Positron fraction Antiproton fraction PAMELA released data on the positron/electron ratio up to about 100 GeV, which show clear excess above ~10 GeV. The low energy data is affected by the solar environment and we do not need care it too much. Nature 458, 607 (2009) Phys.Rev.Lett.102:051101,2009 390 citations after submitted on 28th Oct. 2008, 1paper per day

The total electron+positron spectrum ATIC bump Fermi excess Chang et al. Nature456, 362 2008 Phys.Rev.Lett.102:181101,2009

Possible explanations Astrophysical sources Exotic sources Nearby SNRs, pulsars Propagation Early SN stage interaction of CRs Dark matter annihilation Dark matter decay

Possible origins of e+e-: pp interaction (Blasi, 0903.2794) Occur at the cosmic ray acceleration source: hard spectrum If we consider some new processes, we may first consider within cosmic rays physics Comment: nature for Fermi spectrum; antiprotons may set constraints on this picture

From CRs interaction There is knee in CR spectrum at ~10^15 eV (Hu, Bi et al., 0901.1520) There is knee in CR spectrum at ~10^15 eV It is proposed the knee is generated by interaction, with Eγ=1eV, the threshold energy is at ~10^15 eV 3% converted can explain the ATIC or Fermi Fermi excess Pamela is related with knee; the knee is at knee; knee is generated by the pair production. It should be noted that for 1ev the threshold energy is just at the knee. By simulation

Nearby pulsars

Astrophysical sources D. Hooper et al. S. Profumo …… Nearby pulsars:

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 OK

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 OK OK OK

How to have so large flux Very large annihilation cross section, much larger (~1000) than the requirement by relic density. 1) nonthermal production, ,suppress gamma 2) Sommerfeld enhancement 3) Breit-Wigner enhancement 4) dark matter decay.

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 enhancement Yuan, Bi, Liu, Yin, Zhang and Zhu, Astro-ph/0905.2736

J. Zavala, M. Vogelsberger, and S. White, Astro-ph/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 Constraint on the central density of DM Tension Bi et al., 0905.1253 Constraint on the central density of DM Tension Exist for the annihilating DM scenario, but consistent with decay scenario annihilation decay Liu, Yuan, Bi, Li, Zhang, 0906.3858

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 OK OK OK

Summary ATIC DM Fermi Annihilation: how to boost? Strong constraints! Decay: how to get such long life time, ~1026s Astrophysical sources: difficult to test; (century problems: origin of CRs, knee of CRs