Lars Bergström Department of Physics Stockholm University physto.se

Transcription

1 Lars Bergström Department of Physics Stockholm University physto.se c n TAUP, Seattle, September 6, 2003 MACHOs

2 Basic facts: Ω i ρ ρ 2 3H0m ρcrit = 8π H h 100 kms i crit 2 Pl 0 1 = 1.88h Mpc g / cm 3 Observations give 0.6 < h < 0.8 Big Bang nucleosynthesis (deuterium abundance) and cosmic microwave background (WMAP) determine baryon contribution W B h 2» 0.02, so W B» 0.04 W lum» (4 ± 2) (stars, gas, dust) => baryonic dark matter has to exist (maybe as warm intergalactic gas?) But, if W M > 0.06, there has to exist nonbaryonic dark matter! Lithium underabundant? K.M. Nollet, 2002

3 SN Ia LCDM WMAP D.N. Spergel et al., astro-ph/ J. Tonry et al., astroph/ The 2dF Galaxy Redshift Survey Final Data Release - 30 June 2003

4 Result from best-fit model for WMAP (for flat Universe): Only 4.4 % baryonic matter, W bb h 22 = ± Around % Cold Dark matter, W CDM CDM h 22 = ± 0.01 Around % Dark energy, W L = 0.73 ± 0.04 Age of of Universe: Gyr W W nn h 22 <

5 Real 2dF data Mock LCDM data Large-scale structure is is in in striking agreement with the Concordance Model, ΛCDM (Ω (Ω M = 0.3, Ω Λ = 0.7) Mock LCDM data C. Frenk, 2002

6 Galaxy cluster CL , z = 0.4 Singular isothermal sphere Strong + weak lensing reconstruction of of density profile (Kneib et et al, al, astro-ph/ ) CDM N-body fit (Navarro, Frenk & White)

7 Dark matter needed on all scales! ( MOND and other ad hoc attemps to modify Einstein or Newton gravity very unnatural & unlikely) Galaxy rotation curves X-ray emitting clusters NED/STScI; E. Corbelli & P. Salucci (1999) Cluster 3C295 (Chandra)

8 Since (Super-K), we we know that that non-baryonic dark matter exists! Dm Dm n n 0 m n n 0 However, neutrinos are are not notthe the main component of of dark matter (10% at at most) :: Pauli principle cannot clump in in dwarf halos Galaxy distribution limit limit on on sum sum of of n masses WMAP: S m n < n ev, ev, depends on on analysis of of Ly-a Ly-aforest Ø. Ø. Elgarøy & O. O. Lahav Lahav (2DF (2DF Collaboration), 2003; 2003; S. S. Hannestad astroph/ : S m n astro- < n 1 ev ev (depending on on priors priors and and n chemical potential) Allen, Allen, Schmidt & Bridle Bridle (astroph/ ) find find S m n (astro- = n ev ev if if s 8 8» (from (from X-ray X-rayluminosity function). Future Future galaxy galaxy surveys surveys + Planck Planck satellite satellite (CMBR) perhaps m n» n Dm atm Dm n atm» n ev ev may may be be detectable! (Hu, (Hu, Eisenstein & Tegmark, 1998) 1998) W n = 0.01 W n = dF

9 MACHOs (low-mass stars and Jupiters ) cannot be be major part of of halo dark matter: Summary of of EROS (C. Afonso et et al, al, A&A 2003) and MACHO results (C. Alcock et et al, al, ApJ 2001): MACHO EROS Yoo, Chanamé & Gould, astro-ph/ : The end of of the MACHO era (stability of of wide binaries)

10 Cold Dark Matter Part of the Concordance Model Gives excellent description of CMB, large scale structure, Lya forest, gravitational lensing, supernova distances If consisting of particles, may be related to electroweak mass scale: weak cross section, non-dissipative Weakly Interacting Massive Particles (WIMPs). Potentially detectable, directly or indirectly. May or may not describe small-scale structure in galaxies: Controversial issue, but alternatives (self-interacting DM, warm DM, self-annihilating DM) seem worse. Probably nonlinear astrophysical feedback processes are acting (bar formation, tidal effects, mergers, supernova winds, ). This is a crucial unsolved problem of great importance for dark matter detection rates. See Ben Moore s talk.

11 Good particle physics candidates for Cold Dark Matter: Independent motivation from particle physics; detectable by other means than through gravity only Axions (introduced to solve strong CP problem) Weakly Interacting Massive Particles (WIMPs, 3 GeV < m X < 50 TeV), thermal relics from Big Bang: Supersymmetric particles Heavy neutrino-like particles Braneworld and Kaluza-Klein states Mirror particles Little Higgs Non-thermal (maybe superheavy) relics The WIMP miracle : for typical gauge couplings and masses of order the electroweak scale, W wimp h 2» 0.1 (within factor of 10 or so)

12 Other WIMP candidate: Right-handed neutrino (Krauss, Nasri & Trodden; Baltz & L.B., 2002) Usual see-saw mechanism M R = R O(M GUT ) GUT ) thermal production not not possible (needed annihilation cross section would violate unitarity) Zee Zee model: neutrino masses generated by by loops with with new new charged scalar. Krauss, Nasri, Trodden: discrete symmetry mass generated at at 3 loops TeV TeV scale N R R sufficient Leptonic WIMP ( LIMP )

13 Axion: may solve strong CP CP problem & DM problem Courtesy of G. Raffelt DAMA/NAI S. S. Asztalos et et al., al., 2002 (Livermore) projected C. C. Eleftheriadis et et al., al., (CERN) astro-ph/

14 Supersymmetry Invented in the 1970 s Necessary in most string theories Restores unification of couplings Solves hierarchy problem Gives right scale for neutrino masses Predicts light Higgs ( < 130 GeV) May be detected at Fermilab/LHC Gives an excellent dark matter candidate (If R-parity is conserved stable on cosmological timescales) Useful as a template for generic WIMP (Weakly Interacting Massive Particle) The lightest neutralino: the most natural SUSY dark matter candidate 0 ~ 0 ~ 0 ~ 0 = a 1γ ~ + a2z + a3h1 + a4 2 χ ~ H

15 DM need not necessarily be neutralino Super-WIMPS (Feng, Rajaraman and Takayama, 2003) Example: light gravitino, produced through decay by neutralino -> g + SM particle only gravitationally interacting DM This point may explain 7 Li anomaly Neutralino decay may be seen at LHC

16 Model for Neutralino Galactic Halo: ρ local 0.3 GeV/cm 3, v/c 10-3, m χ 100 GeV flux 10 3 cm -2 s -1 sr -1!

17 W CDM ~ in Concordance Model instead of W CDM ~ 1 in the Standard CDM of the 1980 s Good news for dark matter searches! Explanation: W DM ~ 1/(s ann v) for thermal relics Crossing symmetry s scatt ~ s ann Thus, low W DM (if enough to make up galaxy halos) means higher annihilation & scattering rates (cf. G. Gelmini et al., 2002) One tool for calculation: DarkSUSY fortran code, P. Gondolo, J. Edsjö, L.B., P. Ullio, Mia Schelke and E. A. Baltz

18 DarkSUSY scan Chattopadhyay, Corsetti & Nath, Ω > 0.95 Ωh 2 = 0.11±0.01 (WMAP) 10-7 pb hyperbolic /focus point branch MSSM m GeV M 2 GeV tan b 1 m A GeV m 0 GeV A b /m 0 1 Min Max Parameter Unit A t /m 0 1 MSSM is a low-energy effective theory whereas msugra sets values of parameters at GUT scale. Radiative EW symmetry breaking value of m fixed in msugra, but sign is free. msugra cf. J. Ellis & al, H. Baer et al, J. Edsjö et al

19 Methods of WIMP Dark Matter detection: Discovery at accelerators (Tevatron II, LHC,..) Direct detection of halo particles Indirect detection of neutrinos, gamma rays, radio waves, antiprotons, positrons dσ dq si χ χ 1 = π v 2 2 [ Zf + ( A Z) f ] F ( q A ) 2 p n A The basic process for indirect detection is annihilation, e.g, neutralinos: Neutralinos are Majorana particles χ q e + γ ν χ Γ ann n χ 2 σv Enhanced for clumpy halo; near galactic centre and in Sun & Earth

20 Direct detection by DAMA controversial issue since TAUP 1997 EDELWEISS R. Bernabei et al, astro-ph/ kg days, 6s effect! Moving target? DAMA DAMA 129 Xe Zeplin EDELWEISS Kurylov & Kamionkowski, hepph/ Direct detection: a field in rapid development - see talks by Seidel and Morales

21 To To match WMAP precision on on W CDM CDM h 22,, high-precision relic density calculations are needed. Example: coannihilations in in msugra Edsjö, Gondolo, Schelke & Ullio, 2003 DarkSUSY now accurate to 1 %. (cf Ellis, Falk, Olive, 1998, Nihei et al, 2002, Baer & al 2002, Gomez & al, 2002, Bednyakov et al, 2002, )

22 A. A. Bottino et et al, al, 2003: Low Low mass (M (M < GeV) window (relaxing standard GUT assumption M 1» 1 M 2 /2) 2 /2) DAMA region EDELWEISS CDMS Hooper & Plehn, 2002

23 Indirect detection: annihilation of neutralinos Usually, the heaviest kinematically allowed final state dominates (b or t quarks; W & Z bosons) Note: equal amounts of matter and antimatter in annihilations - source of antimatter in cosmic rays? Decays from neutral pions: Dominant source of continuum gammas in halo annihilations

24 Antiprotons at low energy can not be produced in pp collisions in the galaxy, so that may be DM signal? However, p-he reactions and energy losses due to scattering of antiprotons low-energy gap is filled in. BESS data compatible with conventional production by cosmic rays. Antideuterons better signal but rare? (Donato et al., 2000) L.B., J. Edsjö and P. Ullio, 2000 Bieber & Gaisser, 2000 F. Donato et al., 2003

25 Positrons from neutralino annihilations explanation of feature at GeV? New experiments will come: Pamela (2004) and AMS (2005) Baltz, Edsjö, Freese, Gondolo 2002; Kane, Wang & Wells, 2002

26 Kaluza-Klein Dark Matter (Universal extra dimensions) Cheng, Feng & Matchev, 2002, Kribs & Hooper, Majumdar, 2002, Bertone, Servant & Sigl, Sigl, Main new new effect: bosonic DM, DM, no no chirality suppression Direct detection and and positrons are are best best methods (but (but mass degeneracies are are crucial to to get get detectable signals) Cheng, Feng & Matchev PRL 2002 Positrons Spin-dep Spin-indep

27 Indirect detection through g-rays. Two types of signal: Continuous (large rate but at lower energies, difficult signature) and Monoenergetic line (small rate but at highest energy E g = m c ; smoking gun ). Advantage of gamma rays: point back to the source. Enhanced flux possible thanks to halo density profile and substructure (as predicted by CDM) L.B., P.Ullio & J. Buckley 1998 Gamma-rays continuous γ γ line, χχ γγ m χ = 50 GeV m χ = 300 GeV

28 Loop-induced 2g (or Zg) final state: source of nearly monoenergetic photons v/c 10-3 (for γ γ) or (for Zγ) E Eγ m χ γ m γ 2 mz ( 1 2 4m χ ) L.B. & P. Ullio, 1998 Rates are remarkably large (B.R ) for higgsino-like neutralinos (in particular, also for TeVscale higgsinos). New calculation of higher order effects by Hisano, Matsumoto & Nojiri, PRD 2003.

29 Explosive particle annihilation (Hisano, Matsumoto, Nojiri hep-ph/ ) At m χ ~ 1 TeV, EW interactions get strong Wino-like Higgsino-like Short distance Long distance Gamma-ray line cross sections enhanced by large factors

30 USA-France-Italy-Sweden-Japan (-Germany) collaboration, launch 2006 GLAST will also likely detect a few thousand new GeV blazars

31 Major uncertainty for gamma-ray detection from galactic center: Halo dark matter density distribution. Fits to to N-body simulations Fits to to rotation curves Fit Fit to to lensing (elliptical galaxies) Berezinsky, Gurevich, Zybin model ρ ρ ρ Moore NFW Burkert ( r) = ( r) = ( r) = r 3/ 2 c r( a + ( r c ρcis( r) = 2 a + r c ρsis ( r) = ; 2 r c ρbgz ( r) = ; 1.8 r ( a 2 3/ 2 r) ; c 2 ; c + a)( a + 2 r + 3/ 2 r 2 ; ) ; )

32 1 dl J ( nˆ; Ω) dω Ω (8.5 kpc) r ρ ( ) 0.3 GeV / cm 3 2 Note large uncertainty of flux for nearby objects (Milky Way center, LMC, Draco, ) In this region (at cosmological distances), the uncertainty is much less P. Ullio, L. B., J. Edsjö, 2002

33 GLAST simulation Gamma-ray excess towards Galactic center may be be explained by by WIMP annihilation A. Cesarini et al, astro-ph/

34 B = B eq Bertone, Sigl & Silk, 2001 Sub-mm bump due to processes in accretion disk? m χ = 500 GeV Simultaneous fit to radio emission (408 MHz) and EGRET g-ray spectrum possible if halo is mildly singular r(r) 1/r 0.1, enhanced by formation of spike.

35 Milky Way simulation, Helmi, White & Springel, 2002 Stoehr, White, Springel,Tormen, Yoshida, astro-ph/ , cf. Berezinsky, Dokuchaev, Eroshenko, astro-ph/ ; Hofmann, Schwarz, Stöcker, 2001; Gnedin & Primack, 2003

36 Problems with WIMP interpretation of of detected gammarays from Galactic center: What is is the the cause of of the the background distribution (SNR s, inverse Compton & bremsstrahlung, )? )? How How parametrize it? it? Are Are there other point sources in in the the vicinity (Hooper & Dingus, 2002)? What is is the the WIMP halo halo profile (cusp, spike, core, )? )? Effects of of interaction with with black hole, dense stellar cluster, Is Is there an an excess beyond EGRET s measurements (CANGAROO reports TeV TeV excess )? )? GLAST and new Air Cherenkov Telescopes may perform a more convincing angular and spectral mapping. Gammaray line would be be spectacular, but rate uncertain

37 Diffuse cosmic gamma-rays Points should move down as GLAST resolves more blazars Idea: Redshifted gamma-ray line linegives peculiar energy feature may maybe be observable for for CDM-type (Moore profile) cuspy halos and and substructure Ullio, Bergström & Edsjö, 2002

38 E.A. Baltz & L.B., 2003 Predicted gamma-ray signal towards galactic center for for leptonic WIMP (NFW profile assumed) Only coupling to to leptons no no direct detection, no no neutrino signal from Earth & Sun, Sun, no no antiproton signal. Gamma-rays (and (and perhaps positrons) are are the the only only hope for for detection. Air Air Cherenkov Telescopes (HESS) & GLAST provide window of of opportunity.

39 Conclusions Existence of nonbaryonic dark matter more certain than ever CDM favoured Neutrinos and MACHOs only small part of dark matter Supersymmetric particles (neutralinos) are among the bestmotivated candidates New direct and indirect detection experiments will reach deep into SUSY parameter space DAMA still sees annual modulation Indications of gamma-ray excess from Galactic center The various indirect detection methods are complementary to each other and to direct detection SUSY WIMPs are generic, but there exist alternatives The hunt is going on many new experiments coming!