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Lars Bergström The Oskar Klein Centre for Cosmoparticle Physics Dept. of Physics Stockholm University lbe@physto.s

Indirect detection of dark matter: uncertainties and possibilities. Lars Bergström The Oskar Klein Centre for Cosmoparticle Physics Dept. of Physics Stockholm University lbe@physto.se. PAMELA Workshop, Roma, May11, 2009. Via Lactea II simulation (J. Diemand & al, 2008).

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Lars Bergström The Oskar Klein Centre for Cosmoparticle Physics Dept. of Physics Stockholm University lbe@physto.s

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  1. Indirect detection of dark matter: uncertainties and possibilities Lars Bergström The Oskar Klein Centre for Cosmoparticle Physics Dept. of Physics Stockholm University lbe@physto.se PAMELA Workshop, Roma, May11, 2009

  2. Via Lactea II simulation (J. Diemand & al, 2008) Lots of clumps of dark matter in the halo! Strategy for identifying DM usingindirectdetection Gamma-rays from DM shoulddirectlyreflect the spatial distribution of the halo. No diffusion of gamma-rays, and simple energy loss for positrons  possiblefingerprints of DM also in the energyspectrum. Otherprobes (radio, CMB, X-rays, antiprotons, neutrinos) should be withinobservationalbounds Furtherenhancementpossiblethrough the Sommerfeldeffect (see later).

  3. Indirect detection, example: annihilation of neutralinos in the galactic halo Majorana particles: helicity factor for fermions v  mf2 Note: equal amounts of matter and antimatter in annihilations Decays from neutral pions, kaons etc: DarkSUSY uses PYTHIA. One-loop effect: 2 or Z final state gives narrow lines. Internal bremsstrahlung also contributes to high-energy gammas

  4. 3 exclusion limit, 1 year of GLAST data Note: the regions with high gamma rates are very weakly correlated with models of high direct detection rates  complementarity ”Conservative” approach, g.c., NFW halo profile assumed, no substructure. Including all halo, with substructure Vast region of opportunity for next generation of gamma-ray instruments! (And maybe detectable by Fermi if there is a Sommerfeld enhancement.) Cf. GLAST working group on Dark Matter and New Physics, E.A. Baltz, et al., arXiv:0806.2911

  5. Recent development: New observational signature for Majorana particles (like neutralinos)  f  mf for Majorana particles in limit v/c  0  f _ ”Internal bremsstrahlung”, IB ”Final state radiation”  mf Simplest example  mf No mf suppression! 5 L.B., 1989; T. Bringmann & al, 2007-8

  6. QED corrections (InternalBremsstrahlung) in the MSSM: good news for detectionprobability in gamma-rays: T. Bringmann, L.B., J. Edsjö, JHEP, 2008 Example: benchmarkpoint BM3, mass = 233 GeV, fulfils all accelerator constraints, has WMAP-compatiblerelicdensity (staucoannihilation region). New calculationincludingInternalBremsstrahlung (DarkSUSY 5.0). Spectraldrop att 233 GeV is nicelyinside the GLAST range… Previous estimate of gamma-ray spectrum (DarkSUSY 4.1) 6

  7. Some of the newly found dwarf galaxies may give favourable rates: L. Strigari & al, 2008 MAGIC Oct. 2008: Boost factors corresponding to upper limits from Willman I, needed to see a signal Much more observing time needed. (So far, only 15 hours.) The future CTA may be ideal instrument. T. Bringmann & al, 2008

  8. The future of GeV - TeV gamma-rays astronomy? Possible Cherenkov Telescope Array (CTA) sensitivity GLAST Crab E.F(>E) [TeV/cm2s] 10% Crab MAGIC Similarproject in the US: AGIS. Will CTA and AGIS merge? CTA H.E.S.S. 1% Crab W. Hofmann

  9. ”EGRET excess of gamma-rays” Has supersymmetric dark matter already been seen in indirect detection? W. de Boer, 2003-2008 Filled by 65 GeV neutralino annihilation Galactic rotation curve Data explained by 50-100 GeV neutralino? New CDMS limit, 2008

  10. Expected antiproton flux from de Boer’s supersymmetric models (with standard diffusion) Standard (secondary) production from cosmic rays Stecker & al 2007: EGRET GeV anomaly may be instrument calibration error. L.B., J. Edsjö, M. Gustafsson & P. Salati, 2006

  11. What are the results for the inner Galaxy? And high latitudes – This is where DM could be important… stayed tuned for more Fermi data.

  12. Oct 2008: The awaited PAMELA data on the positron ratio up to 100 GeV . (O. Adriani et al., Nature 458, 607 (2009)) A very important result! An additional, primary source of positrons is needed. Prediction from secondaryproduction by cosmicrays: Moskalenko & Strong, 1998

  13. M. Simet and D. Hooper, 2009

  14. 1. Positrons generated by a class of extreme objects: supernova remnants (pulsars): • So, new modeling is needed. Twomainpossibilities come to mind: • Pulsars (or other supernova remnants) • Dark Matter Geminga pulsar estimates Vela pulsar (supernova remnant) Yuksel, Kistler, Stanev, 2008 (cf. Aharonian, Atoyan and Völk, 1995; Kobayashi et al., 2004)

  15. 2. Example of DM solution: SUSY with internalbremsstrahlung and largeboostfactors, or Winos with unusualpropagation parameters cangive the right spectrum: P. Grajek, G.L. Kane, D. Phalen, A. Pierce,and S. Watson. arXiv:0812.4555 However, does not explain new electron plus positron data (see later)

  16. V for positrons – can give large boost if nearby dark matter clump (unlikely) – enhanced cross section needed (e.g., Sommerfeld enhancement)

  17. V for gamma rays – can give very large boost factors in directions where dark matter is concentrated (the galactic center; subhalos)

  18. The Sommerfeld enhancement: Well- known in electrodynamics, newly discovered in DM physics: Hisano, Matsumoto and Nojiri, 2003; Hisano, Matsumoto, Nojiri and Saito, 2004, expanding on the 2g calculation of L.B. and P. Ullio (1998): Neutralino and chargino nearly degenerate; attractive Yukawa force from W and Z exchange  bound states near zero velocity, ”Sommerfeld resonance”  enhancement of annihilation rate for small (Galactic) velocities. Little effect on relic density (higher v). ”Explosive annihilation”!

  19. wino higgsino In MSSM without standard GUT condition (AMSB; split SUSY) mwino 2 – 3 TeV; m ~ 0.2 GeV Factor of 100 – 1000 enhancement of annihilation rate possible. B.R. to  and Z is of order 0.2 – 0.8! F. Boudjema, A. Semenov, D. Temes, 2005 Non-perturbative resummation explains large lowest-order rates to  and Z. It also restores unitarity at largest masses See also M. Cirelli & A. Strumia, 2008, N. Arkani-Hamed, D. Finkbeiner, T. Slatyer and N. Weiner, 2008, M. Lattanzi & J. Silk, 2008,…

  20. Lattanzi & Silk, 2008 M. Cirelli and M. Strumia, 2008; M. Lattanzi and J. Silk, 2008; N. Arkani-Hamed , D. Finkbeiner, T. Slatyer and N. Weiner, 2008; J. Bovy, 2009,… Dark matterparticles (WIMPS) move with velocities v/c  10-3. Non relativisticcalculation is accurate and sufficient  The boost ”problem” is solved for DM!

  21. V for antiprotons – can not give large density boost factor for realistic halo models. PAMELA data on pbar ratio  No Sommerfeld enhancement possible either for antiprotons  ”leptophilic” models for DM preferred.

  22. F. Donato, D. Maurin, P. Brun, T. Delahaye and P. Salati, Phys.Rev.Lett.102:071301,2009 Not much room for an exotic component giving antiprotons!

  23. What the PAMELA data – positron fraction and antiproton ratio - tellus, ifrelated to DM: Wehave to look for modelsannihilatingpreferentially to leptons, and that have a Sommerfeld or similarenhancement. With previous ”canonical” models (e.g. MSSM) it is verydifficult. (DM decay in principlepossible, butone has to fine-tunedecay rate.)

  24. The Kaluza-Klein theory of extra dimensions: The lightest KK boson may be a dark matter WIMP Oskar Klein, 1894-1977 (Also Klein paradox, Klein-Nishina formula, Klein-Gordon equation, Klein-Jordan quantization, pre-gauge theory of SU(2), Alfvén-Klein cosmology) Theodor Kaluza, 1885-1954 Pre-PAMELA prediction of positron fraction: D. Hooper and S. Profumo, Phys.Rept.453:29-115,2007

  25. Cosmic ray diffusion, positrons and electrons Positrons lose direction almost immediately, and lose energy continuously. Diffusion equation (see, e.g., Baltz and Edsjö, 1999): = 0 (steady state) Energy-dependent diffusion coefficient Energy loss (mostly synchrotron and Inverse Compton) Source term (from annihilation) =1/0 At high energies (> 50 GeV), the diffusion term  K(E) is negligible!

  26. Simple formula for the electron and positron yield at E > 50 GeV (the no spatial diffusion limit – only energy diffusion): For direct annihilation to electrons and positrons, which means a very simple formula for the positron plus electron flux from DM in the solar neighbourhood: with enhancement factor

  27. HESS, Nov. 24, 2008 Nature, November 19, 2008 ATIC: Balloon experiment which measures sum of electron and positron flux Is the dark matter feature really there? Fermi can measure this spectrum to 1 TeV with superior statistics (but not so good energy resolution, 10-15% compared to 2-3% for ATIC).

  28. Prediction of DM- induced electrons and positrons, EF = 200. Pre-Fermi GALPROP bkg Total spectrum (3 % energy resolution, ATIC) ATIC 1+2+4 data sets displayed (see Isbert’s talk)

  29. Prediction of DM- induced electrons and positrons, EF = 200. Pre-Fermi GALPROP bkg Total spectrum (15 % energy resolution, Fermi) ATIC 1+2+4 data sets displayed (see Isbert’s talk)

  30. Prediction of DM- induced electrons and positrons, EF = 200. Pre-Fermi GALPROP bkg Total spectrum (15 % energy resolution, Fermi) ATIC 1+2+4 data sets displayed (see Isbert’s talk) New Fermi, and HESS (2 data sets) added

  31. Prediction of DM- induced electrons and positrons, EF = 200. Pre-Fermi GALPROP bkg ATIC 1+2+4 data sets removed (see Moiseev’s talk) New Fermi, and HESS (2 data sets) added Obvious problems with relative normalizations. Solution: rescale GALPROP and HESS by 0.85

  32. Prediction of DM- induced electrons and positrons, EF = 200. Pre-Fermi GALPROP bkg ATIC 1+2+4 data sets removed (see Moiseev’s talk) New Fermi, and HESS (2 data sets) added Obvious problems with relative normalizations. Solution: rescale GALPROP and HESS by 0.85. Done!

  33. Modify the injection indices of GALPROP? D. Grasso et al., arXiv:0905.0636 Does not fit at all the PAMELA ratio:

  34. DM predictions: Note model independence of this slope! M. Kuhlen and D. Malyshev, arXiv: 0904.3378

  35. Independence also of halo profile. By changing diffusion parameters, one may also change the low-energy part somewhat – may improve agreement with PAMELA positron fraction. The high-energy prediction is really universal, though. M. Kuhlen and D. Malyshev, arXiv: 0904.3378

  36. L.B., J. Edsjö and G. Zaharijas, arXiv:0905.0333 Contribution from k=2 muonic model, Mass = 1.6 TeV, EF = 1100

  37. Note this rising part! E. Borriello, A. Cuoco and G. Miele, arXiv:0903.1852 Borriello et al. Happened to choose almost the same mass, but higher enhancement by a factor of 3. Final state radiation could be the ”smoking gun” for dark matter! Fermi and ACT:s would have a chance to see this!

  38. The pulsar situation Geminga pulsar estimates Vela pulsar (supernova remnant) Yuksel, Kistler, Stanev, 2008 (cf. Aharonian, Atoyan and Völk, 1995; Kobayashi et al., 2004)

  39. D. Grasso et al., arXiv:0905.0636 New GALPROP model (post-Fermi), rescaled by 0.95

  40. Reasonable fit to PAMELA

  41. S. Profumo, arXiv:0812.4457

  42. D. Malyshev, I. Cholis and J. Gelfand, arXiv:0903.1310

  43. Some structure in the curve should eventually be seen for pulsars? (D. Grasso et al., 2009).

  44. Comparing pulsars with DM

  45. Finally, a sobering picture: The spectrum without the E3 factor Is this almost perfect fit only a fluke?

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