Lars Bergström Department of Physics Stockholm University · Kashiwa Symposium Lars Bergström,...

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Kashiwa Symposium Lars Bergström, [email protected]

Lars Lars BergstrBergströömmDepartment of PhysicsDepartment of PhysicsStockholm UniversityStockholm University


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Basic facts:

Observations give 0.6 < h < 0.8

Big Bang nucleosynthesis and cosmic microwave background determine baryon contribution ΩBh2 ≈ 0.02.

Ωlum ≈ (4 ± 2) . 10-3 (stars, gas, dust) =>baryonic dark matter has to exist (maybe as warm intergalactic gas?)

But, if ΩM > 0.06, there has to exist non-baryonic dark matter!

K.M. Nollet, 2002

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Combined fit using CBI data (J.L. Sievers et al., astro-ph/0205387)

Including LSS

2hCDMc Ω≡ω


New results from DASI (September 19, 2002): Polarisation detected at > 5σ. TE cross-correlation (2-3σ) agrees perfectly with prediction of Concordance Model, ΛCDM (ΩM = 0.3, ΩΛ = 0.7)

DASI team, J. Carlstrom et al. DASI team, J. Carlstrom et al.

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Large-scale structure is in striking agreement with the Concordance Model,

ΛCDM (ΩM = 0.3, ΩΛ = 0.7)

P. Norberg & S. Cole, 2000


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.

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N-body simulations by Ben Moore, http://www.nbody.net

Too many subhalos in CDM? Maybe dark! Gravitational lensing may need subhalos (Dalal & Kochanek, 2002)

CDM radial profile too singular? Observations unclear; baryonic feedback not included in simulations

Simulation of self-interacting dark matter halo - excluded by lensing


Ben Moore, www.nbody.net

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’Milky Way’simulation

Helmi, White & Springel, 2002


de Blok and Bosma 2002:

Rotation curves of low surface brightness galaxies not well fit by CDM?

de Blok and Bosma 2002:

Rotation curves of low surface brightness galaxies not well fit by CDM?

astro-ph/0201276

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soft core1/r (CDM)

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. Self-interacting dark matter ruled out? (Loewenstein andMushotzky, astro-ph/0205359)

New Chandra results on cluster A2029: perfect fit to CDM, cored model ruled out (astro-ph/0209205).


ΩM ~ 0.3 in Concordance Model instead of ΩM ~ 1 in the ”Standard CDM” of the 1980’s→ Good news for dark matter searches!Explanation: ΩDM ~ 1/(σannv)Crossing symmetry ⇒ σscatt ~ σannThus, low ΩDM (if enough to make up galaxy halos) means higher annihilation & scattering rates

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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)• Useful as a template for generic “WIMP” (Weakly

Interacting Massive Particle)

[email protected]


MSSM – Minimal Supersymmetric extension of the Standard Model

R parity conservation (multiplicative quantum number) gives naturaldark matter candidate

• The simplest supersymmetric extension of the Standard Model. Only one supersymmetry generator (N = 1 SUSY) ⇒ one superpartner to each SM particle.

• 2 Higgs doublets required ⇒ 5 physical Higgs bosons.

• Allow most general soft SUSY-breaking terms, preserving R-parity:

The most general R-parity conserving lagrangian has 124 free parameters!We reduce to 7 parameters:µ: Higgsino mass parameterΜ2: Gaugino mass parametertanβ: ratio of Higgs vevsM3: Mass of pseudoscalar Higgs bosonM0 : scalar mass parameterAb, At: Soft trilinear parameters

( ) ( ) SLBR 231 +−−=sparticlesfor 1particlesfor 1

−+

=R⇒

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024

013

021

0 ~~~~~ HaHaZaa +++= γχMost plausible SUSY dark matter candidate: The lightest neutralino

fraction higgsino)1(||||

fraction gaugino||||

;1||

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Neutralinos are Majorana particles (their own antiparticles).

,...,,,~~ 03

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property, Majorana todue However,

dominate. should wave-Shalos galactic in110

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Prime candidate: MSSM χ, thermally produced in the early Universe However, there are other possibilities for Dark Matter related to supersymmetry:

• , sneutrinos (Hall & Murayama, …)

• 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

ν~

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Model for Neutralino Galactic Halo:

ρlocal ∼ 0.3 GeV/cm3, v/c ∼ 10-3, mχ ∼ 100 GeV

⇒ flux 103 cm-2 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

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Loop-induced 2γ (or Zγ) final state: source of nearly monoenergetic photons

L.B. & P. Ullio, 1998

v/c ≈ 10-3 ⇒

or

(for Zγ)

)4

1( 2

2

χγγ m

mmE Z−≈χγ mE ≈

Rates are generally large (B.R. ∝ 10-3 - 10-2) for higgsino-like neutralinos (in particular, also for TeV-scale higgsinos)


Paolo Gondolo, Joakim Edsjö, Lars Bergström,Piero Ullio and Edward A. Baltz

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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 2002 with manual and long paper.• Download at http://www.physto.se/~edsjo/darksusy/• 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

The basic process for indirect detection is annihilation:

χχ

Neutralinos are Majorana particles

vnann σχ2∝Γ Enhanced for

clumpy halo; near galactic centre and in Sun & Earth

χ χq

e+ν

γ

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Direct ”detection” by DAMA – controversial issue


New EDELWEISS results (June, 2002)

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New ZEPLIN I limit

N. Smith, IDM2002, 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, 2002.)

Preliminary


γ line, χχ→γγmχ = 50 GeV

mχ = 300 GeV

continuous γ

L.B., P.Ullio & J. Buckley 1998

Advantage of gamma rays: point back to the source. Enhanced flux possible thanks to substructure (as predicted by CDM)

Indirect detectionthrough γ-rays. Two types of signal: continuous (large rate but at lower energies, difficult signature) and monoenergetic line(small rate but at highest energy Eγ = mχ; ”smoking gun”).

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USA-France-Italy-Sweden-Japan (-Germany) collaboration, launch 2006

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.

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L.B., J. Edsjö and C. Gunnarsson, 2000

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Note models extending to TeV mass range


Possible observable γ-ray sources of Dark Matterannihilation

• 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 2001)

• Other nearby galaxies (M31, M87, …)

• Dwarf galaxies (Draco, Ursa Minor, Sagittarius, …)

• Globular clusters (? Omega Centauri; J. Guy et al 2002)

• Galaxy clusters

• Halo DM clumps without optical counterparts (”unidentifiedEGRET sources”?)

• Diffuse extragalactic signal from all cosmic DM structure

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Major uncertainty for gamma-ray detection from galactic center: Halo dark matter density distribution.

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ρ

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ρFits to N-body simulations

Fits to rotation curves

Fit to lensing (elliptical galaxies)


Note large uncertainty of flux for nearby objects(Milky Way center, LMC, Draco,…)

In this region(at cosmological distances),the uncertainty is much less

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Galactic center source – interesting but highly uncertain

Bergström, Ullio, Buckley 1998

Binney and Evans 2001: 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, 2000)

L.B., J. Edsjö and C. Gunnarsson, 2000

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”Local group” simulation by B. Moore et al., astro-ph/0106271

Fit to NFW profile

Fit to Moore profile

”Draco”

minihalo


SUSY γ-ray signals from Draco (C. Tyler, astro-ph/0203242)

DarkSUSY points

Unrealistic (?) SIS profile 1/r2

assumed

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With NFW or Moore profile, signal seems difficult to detect

Moore profile

SIS


Tasitsiomi and Olinto, astro-ph/0206040 ”Detectability of neutralino clumps in ACTs”

105 MSun clump (Moore profile) at 61 pc distance

DarkSUSY

Aeff = 108 cm2, 100 hr,σθ = 6´, Eth = 50 GeV

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P.Ullio, L.B., J. Edsjö, C. Lacey, astro-ph/0207125

Maximum distance at which a subclump of given mass can be seen

* 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)

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Bertone, Sigl & Silk, 2001

Simultaneous fit to radio emission (408 MHz) and EGRET γ-ray spectrum possible if halo is mildlysingular ρ(r) ∝ 1/r0.1, enhanced by formation of spike.

Sub-mm bump due to processes in accretion disk?

mχ = 500 GeV

B = Beq


(PRL 87 (2001) 251301)

Idea: Redshifted gamma-ray line gives peculiar energyfeature – may be observable for CDM-type cuspy halos and substructure (cf. Taylor & Silk, 2002)

Enhancement due to substructure

Absorption on IR/opticalbackground

Cosmology

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No data in this region (GLAST will cover it)


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Structure may enlarge the annihilation signal by factor 105 – 106!

Eke, Navarro, Steinmetz


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?

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Points should move down as GLAST resolves more blazars


Note: In models with nonthermal production of neutralinos, annihilation rates can be up to 2 orders of magnitude higher!

Ullio (1999); Fujii and Hamaguchi hep-ph/0205044

MSSM

AMSB

Fujii & Hamaguchi

Fujii & Hamaguchi

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Range of predictions for anomaly-mediated SUSY breaking models

GLAST sensitivity curve including halo substructure

Upper rangeof MSSM predictions


New muon g-2 measurement presented Aug. 1, 2002:

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E.A. Baltz & P. Gondolo, astro-ph/0207673:


All modelsg-2 constraint

g-2 result, if due to SUSY, selects models with high continuum gamma rate and low mass

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Note complementarity between direct and gamma-ray detection!


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

Other indirect detection methods(often complementary to γ-rays)

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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


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Positrons from neutralino annihilations – explanation of

feature at 10 – 30 GeV?


Possible signature in CMBR and radio background? (Blasi, Olinto & Tyler, astro-ph/0202049)

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”Benchmarks”: use small number of ”well-motivated” points in SUSY parameter space (Snowmass 2001)

CRESST & CDMS II projected limits GENIUS

Direct detection


Neutrinos

Gamma-rays

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Conclusions

• Existence of dark matter more certain than ever• CDM seems favoured• Supersymmetric particles (neutralinos) are among the best-

motivated 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!

Lars Bergström Department of Physics Stockholm University · Kashiwa Symposium Lars Bergström,...

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