Dark Matter. Evidence for Dark Matter Dark Matter Candidates How to search for DM particles? Recent puzzling observations (PAMELA, ATIC, EGRET)

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1 Dark Matter Evidence for Dark Matter Dark Matter Candidates How to search for DM particles? Recent puzzling observations (PAMELA, ATIC, EGRET) 1

2 Dark Matter 1933 r. - Fritz Zwicky, COMA cluster. Rotation velocity of gallaxies around common center of mass too large for them to be in a bound system. coma In rotation velocity of gallaxies; halo of invisible matter (?) spherical halo of Dark Matter surrounding a gallaxy P. Mijakowski Invisible matter, only gravitational interactions 2

3 Dark Matter Bullet Cluster 2006 r. analysis of mass distribution in the region of passing through gallaxy clusters (1E ) (*) Gravitational lensing gravitational potential (images from Hubble Space Telescope, European Southern Observatory VLT, Magellan) / violet X-rays - Chandra X-ray Observatory (NASA) /rose Mass of gas typically 2x larger than the mass of visible matter in gallaxies Result: concentration of gravitational mass is where gallaxies are Region of X emission: only 10% of the total mass of the system Comparison of both observations makes Dark Matter necessary 1E (*) D.Clowe et al Ap. J. 648 L109 P. Mijakowski

4 Gravitational lensing Einstein's Bullseyes Elliptical galaxies have DM halos as spiral galaxies 4

5 What do we know about? Visible matter (stars, gas): Ω vis = ( 4,6 ± 0,5) 10 5 Baryons visible or invisible calculated from BB nucleosynthesis Total matter deduced from gravitational potential energy of galaxies etc. +0,03 Ω m = 0,24 0,04 Dark matter: +0,02 Ω DM = Ω m Ω b = 0,20 0,04 geometria płaska k=0 Dark energy: 5

6 Dark Matter - candidates Known particles MACHO s (Massive Astronomical Compact Halo Objects), np. brown dwarfs, neutron stars, black holes Neutrinos (Hot Dark Matter - HDM) Postulated particles: Axions < 7% of mass of gallactic halo (exp. EROS) structure formation requires CDM WIMP-s (Weakly Interacting Massive Particles) - slow, massive, neutral particles, weakly interacting with matter (Cold Dark Matter - CDM) P. Mijakowski 6

7 WIMPs (WIMP Weakly Interacting Massive Particle) We are looking for particles: Neutral With long lifetime ( τ ~ Universe lifetime) Massive ( M χ ~ 100 GeV) Weakly interacting a good WIMP candidate: neutralino χ (SUSY) LSP (Lightest Supersymmetric Particle), is stable (conservation of R parity in SUSY) P. Mijakowski σ cm 2 neutralino(χ) 18 GeV < M χ < 7 TeV LEP Examples of diagrams (neutralino) cosmology 7

8 Direct Detection we measure energy of recoiling nuclei resulting from elastic scattering of WIMPs χ + (A,Z) at rest χ + (A,Z) recoil T recoil ~ kev detector Very many experiments are going on, and new projects studied Stay tuned. 8

9 Direct detection current experimental limits WARP(2.3 l. Ar) DAMA NaI, 90% CL region Zeplin II (Xe) Region above lines is excluded with 3σ CL DAMA 1.1x10 5 kg d (7 years, 100 kg NaI) Hidden assumptions: interaction (spin dependance) Galactic Halo Model Edelweiss (Ge) CDMS II, (Ge) (34 kg d) CDMS II, 2007 prediction XENON (10kg) 2007, 136 kg d 9

10 Indirect detection - neutrinos ρ χ χ Sun Earth σ scatt ν µ Γ capture Γ annihilation χ Z ν detektor µ χ In neutrino telescopes no excess of neutrinos from Sun, Earth center, Gallaxy center when compared to the expected background. P. Mijakowski ν 10

11 Super-Kamiokande data sample live days of SK-I 1892 upward through-going muons muon length > 7m E µ >1.6 GeV effective area: 1200 m 2 angular resolution: 1 deg Simulation of the background of atmospheric neutrinos with: Bartol fluxes (1996) (event time sampled from data sample) Nuance for neutrino interactions muon energy loss in rock Lipari, Stanev detector simulation oscillations S. Desai PhD thesis S.Desai et al., PRD D70, (2004) 11

12 Upward-muons (from ν interactions) -SK atm. bkg without oscil Angles with respect to direction from: with oscil. Earthc enter Galactic center Sun with oscil. Normalization: total # of MC events = # of data events No excess of neutrinos from the studied objects Upper limits on muon fluxes are calculated 12

13 Upward muons flux limits from various experiments SK From Galactic center SK From Earth s center From Sun SK 13

14 Muon flux limits as functions of WIMP masses Wimps of larger mass produce tighter ν beams. Cones are calculated containing 90% of muons from WIMPs: Earth s center Sun Galactic center S.Desai et al., Phys.Rev. D70 (2004)

15 SuperK limit for neutralino elastic cross section (spin independent interactions) Comparison with direct detection: model dependent, assuming only spin-independent interactions in Earth and Sun Direct and Indirect event rates: Evt. rate in 1 kg Ge detector = Evt. Rate in m 2 of upward muon detector (assuming SI couplings) comparison with direct detection» Currently: lowest limit in direct detection -> XENON, ~10-7 pb (10-43 cm 2 ) for a 100 GeV WIMP 15

16 SuperK limit for neutralino elastic cross section (spin dependent) Kamionkowski, Ullio, Vogel JHEP 0107 (2001) 044 Limit 100 times lower than from direct search experiments DAMA annual modulation due to axial vector couplings ruled out by this result (Kamionkowski et al.) 16

17 Some recent observations which can indicate Dark Matter particles in Universe 17

18 Cosmic-ray Antimatter from Dark Antimatter particles can result from: Matter annihilation e +, p secondary interactions of primary cosmic rays annihilation of WIMPs gravitationally confined in the galactic halo χ You are here e +, p χ Halo Milky Way A plausible WIMP candidate is a neutralino χ, the lightest SUSY particle Most likely processes: χ + χ qq hadrons p, e +,... χ + χ W + W, Z 0 Z 0,.. e +,... 18

19 PAMELA a Payload for Antimatter Matter Exploration and Light-nuclei Astrophysics PAMELA is mounted on satellite Resurs-DK1, inside a pressurized container launched June 2006 minimum lifetime 3 years data transmitted via Very high-speed Radio Link (VRL) PAMELA scientific objectives:» Search for dark matter annihilation (e + and p-bar spectra)» Search for anti-he (primordial antimatter)» Study composition and spectra of cosmic rays (including light nuclei)» Study solar physics and solar modulation» Study terrestrial magnetosphere and radiation belts 19

20 PAMELA detector principle 20

21 PAMELA results (positrons) best statistics so far: electrons compared to other experiments low energy - solar modulation effects 9430 positrons...in 500 days in GeV difference comparing to CAPRICE, HEAT, AMS -> previous solar cycle 5-10 GeV compatibility with other meas. above 10 GeV observed increase "From (*) O.Adriani neutrinos et al....". [PAMELA DK&ER, Collaboration], arxiv (Oct )

22 PAMELA results (positrons) compared to secondary production (*) O.Adriani et al. [PAMELA Collaboration], arxiv (Oct 2008) secondary production (Moskalenko&Strong) spectrum shape completely different???? 22

23 Baloon born experiment for C.R measurement Operated from McMurdo, Antarctica ATIC-1 15 days (2000/2001) ATIC-2 17 days (2002/2003) 36km ATIC Advanced Thin Ionization Calorimeter 23

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25 ATIC results (*) J. Chang, et al. [ATIC Collaboration], Nature, 456, 362 (2008) e+e- flux ATIC (red points); AMS (green stars); HEAT (open black triangles); BETS (open blue circles), PPB-BETS (blue crosses); emulsion chambers (black open diamonds); solid curve galactic spectrum (GALPROP); dashed curve - solar modulated electron spectrum; 25

26 Neutralino annihilation fit to PAMELA & ATIC data D.Hooper. A.Stebbins,K.Zurek, arxiv (Dec 2008) secondary production (Moskalenko&Strong) ASSUMPTIONS» WIMPs annihilation only to W + W -» Annihilation in nearby clump (could be a point source like) To normalize ATIC & PAMELA data a very large or dense clump of DM is required -> annihilation rates (per second): 26

27 DM annihilation to gammas - EGRET EGRET excess in diffuse galactic gamma ray flux GeV neutralino annihilation? 27

28 Summary Dark Matter consistently needed to understand various astrophysical observations According to current studies it constitutes around 24% of the total energy of the Universe The searches of Dark Matter candidates are going on in various experiments: direct searches indirect searches using neutrinos from WIMP annihilation Recently some puzzling observations (PAMELA, ATIC, EGRET) - could be due to DM?? 28