Preliminary lecture programme:

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Preliminary lecture programme: 1. The particle universe: introduction, cosmological parameters 2. Basic cross sections for neutrinos and gamma-rays; IceCube 3.

1 Preliminary lecture programme: 1. The particle universe: introduction, cosmological parameters 2. Basic cross sections for neutrinos and gamma-rays; IceCube 3. Density of relic particles from the early Universe 4. Dark matter: Direct and indirect detection methods; the galactic centre & other promising DM sources 5. Neutrinos and antimatter from dark matter, Sommerfeld enhancement 6. Particular dark matter candidates (WIMPS, Kaluza- Klein particles, sterile neutrinos, ) 7. Supersymmetric dark matter, DarkSUSY. 8. Diffuse extragalactic gamma-rays, Primordial black holes, Hawking radiation 9. Gravitational waves Lars Bergström, Saas-Fee School,

3 New project within IceCube (initiated and to a large part funded from Sweden): IceCube Deep Core - ICDC Was deployed at the South Pole this season

4 DM detection by neutrinos from the Earth or Sun Capture rate for the Earth (A. Gould, 1987). In the Earth, only spin-0 elements, so spinindependent cross section is decisive. But direct detection experiments also probe spinindependent scattering cross section difficult for neutrino telescopes to compete SUSY WIMP capture in the Sun, A. Bottino, N. Fornengo, G. Mignola, Here much of the capture cross section is from protons, i.e., spin-dependent scattering neutrino telescopes can be competitive Lars Bergström, Saas-Fee School,

5 Change of the DM particle number in the Sun with time: Capture rate Annihilation rate Evaporation rate (for small masses) The present rate is given by t = t SUN = years. If t SUN /t >> 1, then there is equilibrium, dn/dt = 0, and so depends only on the capture cross section! Lars Bergström, Saas-Fee School,

6 The neutrino-induced muon rate in, e.g, the IceCube: Wikström & Edsjö, 2009 muon range muon energy loss muon neutrino oscill. annihilation branching fractions Lars Bergström, Saas-Fee School,

7 Neutrinos from the Sun, IceCube-22 new limits (2009) on spin dependent interactions just about starting to touch the interesting region in parameter space: IceCube Collaboration, R. Abbasi et al., arxiv: ; G. Wikström and J. Edsjö, arxiv:

8 Positrons Oct 2008: The surprising PAMELA data on the positron ratio up to 100 GeV. (O. Adriani et al., Nature 458, 607 (2009)) A very important result (almost 500 citations already)! An additional, primary source of positrons seems to be needed. Prediction from secondary production by cosmic rays: Moskalenko & Strong, 1998

$Tait, 2003): The lightest KK boson may be a dark matter WIMP (see lecture tomorrow) Pre-PAMELA prediction of positron fraction: PAMELA 2008 PAMELA 2008 Problem for KK models: also give quarks and$

9 The Kaluza-Klein theory of universal extra dimensions (T. Appelquist et al, 2001; H.C. Cheng, K. Matchev and M. Schmaltz, 2002; G. Servant and T. Tait, 2003): The lightest KK boson may be a dark matter WIMP (see lecture tomorrow) Pre-PAMELA prediction of positron fraction: PAMELA 2008 PAMELA 2008 Problem for KK models: also give quarks and thus antiprotons (not seen by PAMELA). Boost factor of order 1000 needed. D. Hooper and S. Profumo, Phys. Rep (cf. Feng, Cheng & Matchev, PRL 2002)

10 V for 500 GeV positrons can give large boost if nearby dark matter clump (unlikely)

11 V for 500 GeV antiprotons can not give large boost factor for realistic halo models

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

13 Ways to to get a high boost factor: 1. Nearby Dark Matter clump (unlikely) 2. Non-thermal production (decay of heavy DM; collapse of cosmological defects, ). Then one waves good-bye to the WIMP miracle. 3. Interesting possibility for high-mass WIMPs: Sommerfeld enhancement Hisano, Matsumoto and Nojiri, 2003; Hisano, Matsumoto, Nojiri and Saito, 2004, expanding on the 2g calculation of L.B. and P. Ullio (1998): Ladder diagram (cf. QED bound states)

14 Hisano & al, 2004: wino higgsino Weakly bound states near zero velocity, Sommerfeld resonance enhancement of annihilation rate for small (Galactic) velocities. Little effect on relic density (higher v). Explosive annihilation! See also F. Boudjema, A. Semenov, D. Temes, 2005, M. Cirelli & A. Strumia, 2008, N. Arkani-Hamed, D. Finkbeiner, T. Slatyer and N. Weiner, 2008, M.Lattanzi and J. Silk, 2008,

15 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 matter particles (WIMPS) move with velocities v/c Nonrelativistic calculation is accurate and sufficient The boost problem may be solved for DM!

16 Cosmic ray diffusion, positrons and electrons at very high energy (> 100 GeV) Positrons lose direction almost immediately, and lose energy continuously. Diffusion equation (e.g., Baltz and Edsjö, 1999): = 0 (steady state) Energydependent diffusion coefficient Energy loss (mostly synchrotron and Inverse Compton) =1/t 0 Source term (from DM annihilation) At high energies (> 50 GeV), the diffusion term K(E) is negligible!

17 Simple formula for the electron and positron yield at E > 50 GeV (the no spatial diffusion limit only energy diffusion): E For direct annihilation to electrons and positrons, Q e ( E ) 2 ( M E ) which means a very simple formula for the positron plus electron flux from DM in the solar neighbourhood: d E ( M 1 ) TeV E M [ GeV 3 e e F de with enhancement factor E 0.3 GeV Lars Bergström, Saas-Fee School, t GeV E 0 0 F B F / cm 2 10 s m s sr ]

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

19 Prediction of DMinduced electrons and positrons, E F = 200. Pre-Fermi GALPROP bkg Total spectrum (3 % energy resolution, ATIC) ATIC data sets displayed Lars Bergström, Saas-Fee School,

20 Data (May, 2009) from the Fermi satellite (sum of electrons and positrons): Fermi Collaboration, A.A. Abdo & al, PRL, May, 2009

21 HESS, May, 2009: So, the dark matter interest rapidly decreased Lars Bergström, Saas-Fee School,

Positrons generated by a class of extreme objects: supernova remnants (pulsars): Geminga pulsar estimates Vela pulsar (supernova

22 The ATIC peak disappeared (?). But still there is a weaker bump. At least two possibilities: 1. Pulsars (or other supernova remnants) 2. Maybe still Dark Matter? 1. Positrons generated by a class of extreme objects: supernova remnants (pulsars): Geminga pulsar estimates Vela pulsar (supernova remnant) Yuksel, Kistler, Stanev, 2008 (cf. Aharonian, Atoyan and Völk, 1995; Kobayashi et al., 2004). Acceleration in old Supernova Remnants (Blasi & Serpico, 2009): Prediction of antiproton/proton ratio rising above 100 GeV AMS will test

23 Modify the injection indices of the diffusive model (GALPROP)? D. Grasso et al., arxiv: No, does not fit at all the PAMELA ratio: Neither fits low-energy spectrum: M. Pesce-Rollins, D. Grasso et al., arxiv:

Geminga pulsar estimates D. Grasso et al., arxiv:0905.0636 G. Di Bernardo, G.

24 Geminga pulsar estimates D. Grasso et al., arxiv: G. Di Bernardo, G. Gaggeri & D. Grasso, Fermi Symposium, 2009 D. Malyshev, I. Cholis and J. Gelfand, 2009

25 2. Dark Matter. Example: ATIC peak; not seen by Fermi or HESS M DM = 1.6 TeV, BF=1100, m + m - For DM, annihilation into muons and/or taus seem to be necessary, and isothermal profile. Boost factor around 1000 (L.B., J. Edsjö and G. Zaharijas, PRL 2009) 25

26 Model of Nomura and Thaler, annihilation into a+s, with a m + m -, axion-like, and s scalar (maybe supersymmetric). Sommerfeld enhancement is natural in these models. AMS will test this! L.B., J. Edsjö and G. Zaharijas, PRL 2009

27 Consistency tests: M. Cirelli, P. Panci & P.D. Serpico, Dec NFW profile Cored isothermal profile cf. also I. Cholis, G. Dobler, D. Finkbeiner, L. Goodenough, T. Slatyer & N. Weiner, 2009; M. Papucci & A. Strumia, 2009

28 DM density profiles: The observational situation, S.-H. Oh et al, 2008 a: Effective slope at innermost point The ISO profile seems to fit much better than NFW maybe due to dynamical friction of assembled baryonic material? (e.g., El Zant, Shlosman & Hoffman 2001; Lackner & Ostriker, 2010.) 28

29 Comparing pulsars with DM annihilation Pulsars Dark Matter Known to exist? Yes (discovery year: 1967) Yes (discovery year :1933) Free parameters Many (order of 100?) 4 for PAMELA-consistent models. (2 for branching ratio between different leptons, Mass, Boost factor) Is basic mechanism to give required flux known? Predictions for electron spectrum Smoking gun signature Maybe. (An unclear point is the escape probability could be less than 1%) Should show some bumpiness due to different pulsars contributing Irregular energy structure, perhaps anisotropy (small, at percent level) Yes. Sommerfeld enhancement plus maybe some substructure boost Should have smooth, universal shape at energies in the interval GeV, the high-energy spectrum will depend on where in the decay chain e + e - are created Diffuse galactic gamma-rays could show an excess starting between GeV. Maybe also extragalactic & CMB: Planck

Also need special halo model like cored isothermal (or Burkert) model. This seems OK, from observations of rotation curves.

30 Is the electron plus positron high energy excess caused by Dark Matter annihilation? Maybe, but then need unusual model: Large (Sommerfeld?) boost factor (actually a generic feature for TeV DM models), only annihilation to muons or taus (most probably through intermediate light spin-0 particles). Also need special halo model like cored isothermal (or Burkert) model. This seems OK, from observations of rotation curves. Today indirect detection of DM has, like direct detection, reached a sensitivity such that a signal may be found. Watch out for new results (and, unfortunately, probably even some false leads ) in the near future. These are exciting times, the detective story continues and soon we have LHC in the game. We have to search everywhere! ATLAS detector, LHC

Detecting or Limiting Dark Matter through Gamma-Ray Telescopes

Detecting or Limiting Dark Matter through Gamma-Ray Telescopes Lars Bergström The Oskar Klein Centre for Cosmoparticle Physics Dept. of Physics Stockholm University lbe@physto.se Firenze, February 9, 2009