Lars Bergström Department of Physics Stockholm University

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1 Lars Bergström Department of Physics Stockholm University Basic facts: ρi Ωi ρcrit 3H0m ρ = Pl crit = 1.88h 10 8π H0 h kms Mpc 9 g / cm Observations give 0.6 < h < 0.8 Big Bang nucleosynthesis and cosmic microwave background determine baryon contribution Ω B h Ω lum (4 ± ) (stars, gas, dust) => baryonic dark matter has to exist (maybe as warm intergalactic gas?) But, if Ω M > 0.06, there has to exist nonbaryonic dark matter! K.M. Nollet, 00

2 Combined fit using CBI data (J.L. Sievers et al., astro-ph/005387) Including LSS ωc Ω CDM h New results from DASI (September 19, 00): Polarisation detected at > 5σ. TE cross-correlation (-3σ) agrees perfectly with prediction of Concordance Model, ΛCDM (Ω M = 0.3, Ω Λ = 0.7) DASI team, J. Carlstrom et al. DASI team, J. Carlstrom et al.

3 Large-scale structure is in striking agreement with the Concordance Model, ΛCDM (Ω M = 0.3, Ω Λ = 0.7) P. Norberg & S. Cole, 000 Cold Dark Matter Part of the Concordance Model Gives excellent description of large scale structure, Ly-α forest, gravitational lensing If consisting of particles, may be related to electroweak mass scale: weak cross section, non-dissipative 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.

4 Too many subhalos in CDM? Maybe dark! Gravitational lensing may need subhalos (Dalal & Kochanek, 00) CDM radial profile too singular? Observations unclear; baryonic feedback not included in simulations N-body simulations by Ben Moore, Simulation of self-interacting dark matter halo - excluded by lensing Ben Moore,

5 Milky Way simulation Helmi, White & Springel, 00 de Blok and Bosma 00: Rotation curves of of low surface brightness galaxies not well fit by CDM? astro-ph/00176

6 1/r (CDM) soft core Elliptical galaxy NGC 4636, Chandra X-ray image CHANDRA LIMITS ON NATURE OF DARK MATTER. Dark matter distribution seems highly concentrated, in agreement with CDM. Selfinteracting dark matter ruled out? (Loewenstein and Mushotzky, astro-ph/005359) New Chandra results on cluster A09: perfect fit to CDM, cored model ruled out (astro-ph/00905). Ω M ~ 0.3 in Concordance Model instead of Ω M ~ 1 in the Standard CDM of the 1980 s Good news for dark matter searches! Explanation: Ω DM ~ 1/(σ ann v) Crossing symmetry σ scatt ~ σ ann Thus, low Ω DM (if enough to make up galaxy halos) means higher annihilation & scattering rates

7 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) hisho@icepp.s.u-tokyo.ac.jp May be detected at Fermilab/LHC Gives an excellent dark matter candidate (If R-parity is conserved) Useful as a template for generic WIMP (Weakly Interacting Massive Particle) MSSM Minimal Supersymmetric extension of the Standard Model The simplest supersymmetric extension of the Standard Model. Only one supersymmetry generator (N = 1 SUSY) one superpartner to each SM particle. Higgs doublets required 5 physical Higgs bosons. Allow most general soft SUSY-breaking terms, preserving R-parity: R parity conservation (multiplicative quantum number) gives natural dark matter( candidate ) ( ) + 1 for particles 3 R B L + = 1 S R = { 1 for sparticles The most general R-parity conserving lagrangian has 14 free parameters! We reduce to 7 parameters: µ: Higgsino mass parameter Μ : Gaugino mass parameter tanβ: ratio of Higgs vevs M 3 : Mass of pseudoscalar Higgs boson M 0 : scalar mass parameter A b, A t : Soft trilinear parameters

8 Most plausible SUSY dark matter candidate: The lightest neutralino ~ χ H 4 i= 1 a 1 a a 3 0 ~ 0 ~ 0 ~ 0 = a ~ 1γ + az + a3h1 + a4 i = 1; + a + a 4 Z g Z h gaugino fraction ( = 1 Z g ) higgsino fraction Neutralinos are Majorana particles (their own antiparticles). 0 ~ Tree-level annihilation:χ + χ f f, W W, Z Z, H v 3 10 c However, in galactic due to Majorana ( ~ 0 0 χ ~ χ ) 3 S is 0 0 ( ~ χ ~ χ ) 0 f f m S << 1 forbidden, f ~ 0 0 1,H 3 and halos property, due S - wave to helicity should dominate.,... Prime candidate: MSSM χ, thermally produced in the early Universe However, there are other possibilities for Dark Matter related to supersymmetry:, sneutrinos (Hall & Murayama, ) ν ~ ã, axinos (Kim & Roszkowski, ) Wimpzillas (Kolb & al) superheavy relics Cryptons (J. Ellis & al) superheavy relics Q-balls (Kusenko & al,..), Q χ(non-thermal) Self-interacting DM (Spergel & Steinhardt)? χ DM useful template for generic Weakly Interacting Massive Particle (WIMP) also non-supersymmetric ones

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

10 Loop-induced γ (or Zγ) final state: source of nearly monoenergetic photons v/c 10-3 E mz or Eγ mγ ( 1 ) 4mχ (for Zγ) γ m χ Rates are generally large (B.R ) for higgsino-like neutralinos (in particular, also for TeVscale higgsinos) L.B. & P. Ullio, 1998 Paolo Gondolo, Joakim Edsjö, Lars Bergström, Piero Ullio and Edward A. Baltz

11 Release / download Major code reorganization to make it user-friendly. Tested on RedHat Linux 7.3, LinuxPPC, MacOS X and Alphas. Released now as a fully working beta-version. Full release in autumn of 00 with manual and long paper. Download at If you use it, please sign up on the DarkSUSY mailing list on that page! Methods of SUSY Dark Matter detection: Discovery at accelerators (Tevatron II, LHC,..) Direct detection of halo particles Indirect detection of neutrinos, gamma rays, radio waves, antiprotons, positrons χ χ The basic process for indirect detection is annihilation: Neutralinos are Majorana particles χ q e + γ ν χ Γ ann n σv χ Enhanced for clumpy halo; near galactic centre and in Sun & Earth

12 Direct detection by DAMA controversial issue New EDELWEISS results (June, 00)

13 New ZEPLIN I limit Preliminary N. Smith, IDM00, York DAMA seems completely ruled out! (However, if the halo has a more complicated DM structure with clumps and streams, this need not be so. See A.M. Green, 00.) Indirect detection through γ-rays. Two types of signal: continuous (large rate but at lower energies, difficult signature) and monoenergetic line (small rate but at highest energy E γ = m χ ; smoking gun ). Advantage of gamma rays: point back to the source. Enhanced flux possible thanks to substructure (as predicted by CDM) L.B., P.Ullio & J. Buckley 1998 continuous γ γ line, χχ γγ m χ = 50 GeV m χ = 300 GeV

14 USA-France-Italy-Sweden-Japan (-Germany) collaboration, launch 006 GLAST will also likely detect a few thousand new GeV blazars DarkSUSY: Gammas from the halo The flux in a given direction (averaged or not averaged over detector resolution Ω) can be obtained for continuum gamma rays monochromatic gamma lines from γγ monochromatic gamma lines from Zγ Both differential and integrated fluxes can be obtained.

15 Φ ( nˆ; Ω) S J ( nˆ; Ω); γ Nγ σv 1 S = ; J ( nˆ; Ω) m Ω χ dω l. o. s. (8.5 dl kpc r ρ( ) ) 0.3 GeV / cm 3 Note models extending to TeV mass range L.B., J. Edsjö and C. Gunnarsson, 000 Possible observable γ-ray sources of Dark Matter annihilation Diffuse emission from Milky Way dark matter halo (maybe indicated by EGRET data? Dixon et al. 1997; GeV excess ; ) Excess emission from Galactic Center (maybe indicated by EGRET data? Meyer-Hasselwander et al. 1997; Bertone, Sigl, Silk 001) Other nearby galaxies (M31, M87, ) Dwarf galaxies (Draco, Ursa Minor, Sagittarius, ) Globular clusters (? Omega Centauri; J. Guy et al 00) Galaxy clusters Halo DM clumps without optical counterparts ( unidentified EGRET sources?) Diffuse extragalactic signal from all cosmic DM structure

16 Major uncertainty for gamma-ray detection from galactic center: Halo dark matter density distribution. Fits to N-body simulations Fits to rotation curves Fit to lensing (elliptical galaxies) ρ ρ ρ ρ ρ Moore NFW Burkert CIS SIS ( r) = r c ( r) = a + r c ( r) = ; r 3/ ( a c ( r) = r( a + r) c ( r) = ( r + a)( a 3/ ; c + r ; 3/ ; ) ; + r ) 1 J ( nˆ; Ω) dω Ω (8.5 dl kpc r ρ( ) 3 ) 0.3 GeV / cm Note large uncertainty of flux for nearby objects (Milky Way center, LMC, Draco, ) In this region (at cosmological distances), the uncertainty is much less

17 Galactic center source interesting but highly uncertain Bergström, Ullio, Buckley 1998 Binney and Evans 001: Microlensing data towards bulge indicate low DM density near center. NFW does not fit <J> 100. However, clumps may enhance by at least factor 10 (also maybe spike from black hole; see later) CDM simulation of SUSY gamma-ray sky (Calcaneo-Roldan & Moore, 000) L.B., J. Edsjö and C. Gunnarsson, 000

18 Local group simulation by B. Moore et al., astro-ph/ Fit to Moore profile Draco minihalo Fit to NFW profile SUSY γ-ray signals from Draco (C. Tyler, astro-ph/0034) DarkSUSY points Unrealistic (?) SIS profile 1/r assumed

19 Moore profile SIS With NFW or Moore profile, signal seems difficult to detect DarkSUSY 10 5 M Sun clump (Moore profile) at 61 pc distance Tasitsiomi and Olinto, astro-ph/ Detectability of neutralino clumps in ACTs A eff = 10 8 cm, 100 hr, σ θ = 6, E th = 50 GeV

20 Maximum distance at which a subclump of given mass can be seen P.Ullio, L.B., J. Edsjö, C. Lacey, astro-ph/00715 * Tatsiomis - Olinto Dark matter cusp at Galactic Centre caused by black hole? (Gondolo and Silk, 1999) Very sensitive to merger history of black hole (Kamionkowski, Zhao, Ullio; Nakano & Makino; Merritt & Milosavljevic)

21 B = B eq Bertone, Sigl & Silk, 001 Sub-mm bump due to processes in accretion disk? m χ = 500 GeV Simultaneous fit to radio emission (408 MHz) and EGRET γ-ray spectrum possible if halo is mildly singular ρ(r) 1/r 0.1, enhanced by formation of spike. (PRL 87 (001) 51301) Absorption on IR/optical background Enhancement due to substructure Cosmology Idea: Redshifted gamma-ray line gives peculiar energy feature may be observable for CDM-type cuspy halos and substructure (cf. Taylor & Silk, 00)

22 No data in this region (GLAST will cover it)

23 Eke, Navarro, Steinmetz Structure may enlarge the annihilation signal by factor ! Estimating the extragalactic background - blazars Many uncertainties: spectral index & redshift distribution intrinsic absorption & energy cut-off cascading not included has EGRET isolated the true extragalactic signal?

24 Points should move down as GLAST resolves more blazars MSSM Note: In models with nonthermal production of neutralinos, annihilation rates can be up to orders of magnitude higher! Ullio (1999); Fujii and Hamaguchi hep-ph/ Fujii & Hamaguchi AMSB Fujii & Hamaguchi

25 Range of predictions for anomalymediated SUSY breaking models GLAST sensitivity curve including halo substructure Upper range of MSSM predictions New muon g- measurement presented Aug. 1, 00:

26 E.A. Baltz & P. Gondolo, astro-ph/007673: All models g- constraint g- result, if due to SUSY, selects models with high continuum gamma rate and low mass

27 Note complementarity between direct and gamma-ray detection! Other indirect detection methods (often complementary to γ-rays) Indirect detection through neutralino capture and annihilation at the centre of the Earth or the Sun. However, Earth rates and direct detection rates are strongly correlated neutrinos not competitive with new DM direct detection experiments

28 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 L.B., J. Edsjö and P. Ullio, 1999

29 Positrons from neutralino annihilations explanation of feature at GeV? Possible signature in CMBR and radio background? (Blasi, Olinto & Tyler, astro-ph/00049)

30 Benchmarks : use small number of well-motivated points in SUSY parameter space (Snowmass 001) CRESST & CDMS II projected limits GENIUS Direct detection Neutrinos Gamma-rays

31 Conclusions Existence of dark matter more certain than ever CDM seems favoured Supersymmetric particles (neutralinos) are among the bestmotivated candidates Detection in γ-rays seems very promising if current ideas about structure and substructure formation are correct However, expected rates are uncertain due to unknown details of particle physics parameters and actual halo structure Gamma-ray detection complementary to other direct and indirect detection methods New generation of γ-ray detectors have great potential to observe - or limit - dark matter: please help in the search!