wim de boer, karlsruhe seminar beijing, august 15, 2007 1 dark matter visible by hard gamma rays?...

Wim de Boer, Karlsruhe

Seminar Beijing, August 15, 2007 1

Dark matter visible by hard gamma

rays?

Big Bang

Particle physics

Astroparticle physicsAstronomy

Cosmology13.7 billion years

1 ps

10-34 s

95% of energy in universe of unknown nature



Center of the Coma Cluster by Hubble space telescope ©Dubinski

Discovery of DM in 1933Zwicky, Fritz (1898-1974

Zwicky notes in 1933 that outlying galaxies in Coma cluster moving much faster than mass calculated for the visible galaxies would indicate

DM attractsgalaxies withmore force->higher speed.But still bound!



Do we have Dark Matter in our Galaxy?

RotationcurveSolarsystem

rotation curveMilky Way

1/r



Estimate of DM density

DM density falls off like 1/r2 for v=const.

Averaged DM density “1 WIMP/coffee cup” (for 100 GeV WIMP)



• 95% of the energy of the Universe is non-baryonic 23% in the form of Cold Dark Matter

• Dark Matter enhanced in Galaxies and Clusters of Galaxies but DM widely distributed in halo-> DM must consist of weakly interacting and massive particles -> WIMP’s

• Annihilation with <σv>=2.10-26 cm3/s, if thermal relic

From CMB + SN1a + surveys

DM halo profile of galaxycluster from weak lensing

If it is not darkIt does not matter

What is known about Dark Matter?



Expansion rate of universe determines WIMP annihilation cross section

Thermal equilibrium abundance

Actual abundance

T=M/22Co

mo

vin

g n

um

ber

d

ensi

ty

x=m/TGary Steigmann (

WMAP -> h2=0.1130.009 -> <v>=2.10-26 cm3/s

DM increases in Galaxies:1 WIMP/coffee cup 105 <ρ>. DMA (ρ2) restarts again..

T>>M: f+f->M+M; M+M->f+fT<M: M+M->f+fT=M/22: M decoupled, stable density(wenn Annihilationrate Expansions- rate, i.e. =<v>n(xfr) H(xfr) !)

Annihilation into lighter particles, likequarks and leptons -> 0’s -> Gammas!Only assumption in this analysis:WIMP = THERMAL RELIC!



IF DM particles are thermal relics from early universethey can annihilate with cross section as large as <v>=2.10-26 cm3/s which implies an enormous rate of gamma raysfrom π0 decays (produced in quark fragmentation) (Galaxy=1040 higher rate than any accelerator)

Expect large fraction of energetic Galactic gamma rays to come from DMA in this case.Remaining ones from pCR+pGAS-> π0+X , π0->2γ

(+some IC+brems)This means: Galactic gamma rays have 2 componentswith a shape KNOWN from the 2 BEST studied reactionsin accelerators: background known from fixed target exp. DMA known from e+e- annihilation (LEP)

Conclusion sofar



Example of DM annihilation (SUSY)

Dominant + A b bbar quark pairSum of diagrams should yield<σv>=2.10-26 cm3/s to getcorrect relic density

Quark fragmentation known!Hence spectra of positrons,gammas and antiprotons known!Relative amount of ,p,e+ known as well.

f

f

f

f

f

f

Z

Z

W

W 0

f~

A Z

≈37 gammas



R

Sundisc

Basic principle for indirect dark matter searches

R

Sun

bulge

disc

From rotation curve:

Forces: mv2/r=GmM/r2

or M/r=const.for v=cons.and(M/r)/r2

1/r2

for flat rotation curve

Expect highest DM densityIN CENTRE OF GALAXY

Divergent for r=0?NFW profile1/rIsotherm profile const.

IF FLUX AND SHAPE MEASURED INONE DIRECTION, THEN FLUX ANDSHAPE FIXED IN ALL (=180) SKY DIRECTIONS!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

R1

THIS IS AN INCREDIBLE CONSTRAINT, LIKE SAYING I VERIFYTHE EXCESS AND WIMP MASS WITH 180 INDEPENDENT MEAS.



Instrumental parameters:

Energy range: 0.02-30 GeVEnergy resolution: ~20%Effective area: 1500 cm2

Angular resol.: <0.50

Data taking: 1991-1994

Main results: Catalogue of point sourcesExcess in diffuse gamma rays

EGRET on CGRO (Compton Gamma Ray Observ.)

Data publicly available from NASA archive



Two results from EGRET paper

Enhancement in ringlike structure at 13-16 kpc

Called “Cosmic enhancement

Factor”Excess



Galactic coordinates: longitude l and latitude b

( l,b)=(0,0)=Galactic Center

( l,b)=(0,90)=North Galactic Pole

-900 < latitude b < 900

00 < longitude l < 3600

Galactocentric coordinates(left-handed to be

corotating!)Mathematics usually right-

handed!



Background + signal describe EGRET data!

Blue: background uncertainty

Background + DMA signal describe EGRET data!

Blue: WI MP mass uncertainty

50 GeV

70

I CI C



No SM

Electrons

No SM

Protons

Quarks fromWIMPS

Quarks in protons

What about background shape?

Background from nuclear interactions (mainly p+p-> π0 + X -> + X inverse Compton scattering (e-+ -> e- + ) Bremsstrahlung (e- + N -> e- + + N)Shape of background KNOWN if Cosmic Ray spectra of p and e- known



PYTHIA processes: 11 f+f' -> f+f' (QCD) 2370 12 f+fbar -> f'+fbar' 0 13 f+fbar -> g + g 0 28 f+g -> f + g 213068 g+g -> g + g 151053 g+g -> f + fbar 20 92 Single diffractive (XB) 1670 93 Single diffractive (AX) 1600 94 Double diffractive 70095 Low-pT scattering 0Prompt photon production:14 f+fbar -> g+γ 018 f+fbar -> γ +γ 029 f+g -> f +γ 1115 g+g -> g + γ 0114 g+g -> γ + γ 0

Contribution from various hadronic processes

2 GeV4

816

3264

diff.



Energy loss times of electrons and nuclei

Protons diffuse much faster than energy loss time, so expect SAME shape everywhere. Indeed observed: outer Galaxy can be fitted with same shape as inner Galaxy.

-1 = 1/E dE/dt

univ



Analysis of EGRET Data in 6 sky directions

A: inner Galaxy (l=±300, |b|<50)B: Galactic plane avoiding AC: Outer Galaxy

D: low latitude (10-200)

E: intermediate lat. (20-600)F: Galactic poles (60-900)

A: inner Galaxy B: outer disc C: outer Galaxy

D: low latitude E: intermediate lat. F: galactic poles

Total 2 for all regions :28/36 Prob.= 0.8 Excess above background > 10σ.



Fits for 180 instead of 6 regions180 regions:80 in longitude 45 bins4 bins in latitude 00<|b|<50

50<|b|<100

100<|b|<200

200<|b|<900 4x45=180 bins >1400 data points. Reduced 2≈1 with 7% errorsBUT NEEDED IN ADDITION to 1/r2 profile, substructurein the form of 2 doughnut-likerings in the Galactic disc!

ONE RING COINCIDES WITHORBIT FROM CANIS MAJORDWARF GALAXY which losesmass along orbit by tidal forces

OTHER RING coincides with H2 ring



Background scaling factors agree withexpectations of gas- and CR densities

Background scaling factor = Data between 0.1 and 0.5 GeV/GALPROPGALPROP = computer code simulating our galaxy (Moskalenko, Strong)



x y

z

2002,Newberg et al. Ibata et al, Crane et al. Yanny et al.

1/r2 profile and ringsdetermined from inde-pendent directions

xy

xz

Expected Profile

v2M/r=cons.and

(M/r)/r2

1/r2

for const.rotation

curveDivergent for

r=0?NFW1/r

Isotherm const.

Dark Matter distribution

Halo profile

Observed Profile

xy

xz

Outer Ring

Inner Ring

bulge

tota

lDM

1/r2 halodisk

Rotation Curve

Normalize to solar velocity of 220 km/s



How does DM substructure formfrom tidal disruption of dwarf

galaxies?



The local group of galaxies



The Milky Way and its 13 satellite galaxies

Canis Major

Tidal force ΔFG 1/r3



Tidal streams of dark matter from CM and Sgt

CM

Sgt

Sun

From David Law, Caltech



Artistic view of Canis Major Dwarf just below Galactic disc



Canis Major Dwarf orbits from N-body simulationsto fit visible ring of stars at 13 and 18 kpc

Canis Major leaves at 13 kpc tidal stream of gas(106 M☉ from 21 cm line), stars (108 M☉ ,visible), dark matter (1010 M☉, EGRET)

Movie from Nicolas Martin, Rodrigo Ibatahttp://astro.u-strasbg.fr/images_ri/canm-e.html



N-body simulation from Canis-Major dwarf galaxy

prograde retrograde

Ob

serv

ed

sta

rsR=13 kpc,φ=-200,ε=0.8

Canis Major (b=-150)



Gas flaring in the Milky Way

no ring

with ring

P M W Kalberla, L Dedes, J Kerp and U Haud, http://arxiv.org/abs/0704.3925

Gas flaring needs EGRET ring with mass of 2.1010M☉!



Enhancement of inner (outer) ring over 1/r2 profile 6 (8).Mass in rings 0.3 (3)% of total DM

Inner Ring coincides with ring of dust and H2 -> gravitational potential well!

H2

4 kpc coincides with ring ofneutral hydrogen molecules!H+H->H2 in presence of dust->grav. potential well at 4-5 kpc.



Bergstrom et al. astro-ph/0603632, Abstract:

we investigate the viability of the model using the DarkSUSY package to compute the gamma-ray and antiproton fluxes. We are able to show that their (=WdB et al) model is excluded by a wide margin from the measured flux of antiprotons.

Problem with DarkSUSY (DS):1) Flux of antiprotons/gamma in DarkSUSY: O(1) from DMA. However, O(10-2) from LEP data Reason: DS has diffusion box with isotropic diffusion -> DMA fills up box with high density of antiprotons2) Priors of DARKSUSY.(and other propagation models as well): a) static galactic magnetic fields are negligible b) gas is smoothly distributed c) propagation in halo and disk are the sameALL priors likely wrong and can change predictions for DM seaches by ORDER OF MAGNITUDE (and still ok with all observations!)

Do antiproton data exclude interpretation of EGRET data?



it is shown that Galactic cosmic rays can be effectively confined throughmagnetic reflection by molecular clouds,

Another propagation model including static magnetic fields and gas clouds and anisotropic diffusion

Integral excess of positrons in bulge because positrons are trapped in magnetic mirrors between gas clouds?



The van Allen belts are trapped cosmicrays in magnetic mirrors of earth

Radiation in inner belt: 25 Sv/yr inside space shipLethal dose for human: 3 Sv/hSatellites switch of electronics, wennentering dense radiation areas.



Escape time of cosmic rays andgrammage (distance x density)

10Be (t1/2 = 1.51 Myr) is cosmicClock: lifetime of cosmics 107 yrs.

In GALPROP by large haloIn CHANDRAN: by long trapping.

B/C=secondary/prim.determines grammage. In GALPROP by large haloIn Chandran: by reflectingmagnetic mirrors.

B/C determines grammage

10Be/9Be determines escape time



CHANDRAN model GALPROP model

Preliminary results from GALPROP with isotropic and anisotropic propagation

Summary: with anisotropic propagation you can send charged particleswhereever you want and still be consistent with B/C and 10Be/9Be



511 keV1809 keV (26Al)

Comparing radioactive isotopes with positron distribution (Knödlseder et al.)

Problem: expect most low energy positrons to originate from radioactive nuclei with β+ decay.But these are distributed in bulge AND disk.Positrons mostly in bulge. Why???

Unknown positron source only in bulge?? Light DM?Or simply: relativistic positrons escape indisk and annihilate in bulge?



astro-ph/0509298

NO annihilation in molecularclouds (MC), although 75% ofmass in MC. Why?Either volume of MC too smallOR MC are magnetic mirrorsas postulated by Chandran!



What aboutSupersymmetry?

Assume mSUGRA5 parameters: m0, m1/2, tanb, A, sign μ



EGRET excess interpreted as DM consistent with WMAP, Supergravity and electroweak constraints

Bulk

Too largeboostfactorfor EGRETdata

StauLSP

h<114

LSP largely Bino DM may be supersymmetric partner of CMB

Charginos, neutralinos and gluinos light

WMAP

EGRET

Stau coannihilation

mA resonance



Gauge unification perfect with SUSY spectrum from EGRET

With SUSY spectrum from EGRET + WMAP data and start values of couplings from final LEP data perfect gauge coupling unification!

Up

date

fro

m A

mald

i,

dB

, F

ürs

ten

au

, P

LB

260

1991

SM SUSY

Also b->s and g-2 in agreement with SUSY spectrum from EGRET

NO FREEparameter



Grand Unified Theories

Possible evolution of Universe



Celestial bodies collect DM in their cores by their high density.Annihilation can result in flux of HIGH energy neutrinos from sun (from b-decays or from Z-decays).

Neutrinos can be detected by large detectors,like Super-Kamiokande, Amanda, Ice-Cube, Baksanby the charged current interactions with nuclei,which yields muons in the detectors.

Indirect DM detection from solar neutrinos

EG

RET

SUN



WIMPs elastically scatter off nuclei => nuclear recoilsMeasure recoil energy spectrum in target

Direct Detection of WIMPs

0

0

H,Z

EGRET?CDMS

XENON10

If SUSY particle spectrumknown, elastic scattering X-section can be calculated


Seminar Beijing, August 15, 2007 43Movie from M. Steinmetz, Potsdam

Clustering enhances flux from DMA by factor 20-200 (Dokuchaev et al.)

Galaxy formation starting from quantum fluctuations



Clustering of DM

An artist picture of what we should see if oureyes were sensitive to 3 GeV gamma rays and wewere flying with 220 km/s through the DM halo



8 physics questions answered SIMULTANEOUSLY if WIMP = thermal relic

• Astrophysicists: What is the origin of “GeV excess” of diffuse

Galactic Gamma Rays?• Astronomers: Why a change of slope in the galactic rotation

curve at R0 ≈ 11 kpc? Why ring of stars at 13 kpc? Why ring of molecular hydrogen at 4 kpc? Why S-shape in gas flaring? • Cosmologists: How is DM annihilating?A: into

quark pairs

How is Cold Dark Matter distributed?• Particle physicists: Is DM annihilating as expected in

Supersymmetry?

A: DM substructure

A: DM annihilation

A: standard profile + substructure

A: Cross sections perfectly consistent with mSUGRA for light gauginos, heavy squarks/sleptons



Summary

>>10σ EGRET excess shows intriguing hint that:

WIMP is thermal relic with expected annihilation into quark pairs

SPATIAL DISTRIBUTION of annihilation signal is signature for DMAwhich clearly shows that EGRET excess is tracer of DM by fact thatone can construct rotation curve and tidal streams from gamma rays.

DM becomes visible by gamma rays from fragmentation(30-40 gamma rays of few GeV pro annihilation from π0 decays)

Results rather model independent, since only KNOWN spectral shapes of signal and background used, NO model dependent calculations of abs.fluxes.Different shapes or unknown experimental problems may change the gamma ray flux and/or WIMP mass, BUT NOT the distribution in the sky.

DM interpretation strongly supported independently by gas flaring

DM interpretation perfectly consistent with Supersymmetry



Summary on WIMP searches

Indirect detection: (SPACE EXPERIMENTS)

intriguing hint for signals from DMA for 60 GeV WIMP from gamma rays

Direct detection: (UNDERGROUND OBSERVATORIES) expected to observe signal in near future

IF we are not in VOID of clumpy DM halo

Direct production:(ACCELERATORS (LHC 2008-2018)): cannot produce WIMPs directly (too small cross section), BUT IF WIMPs are Lightest Supersymmetric Particle (LSP) THEN WIMPs observable in DECAY of SUSY particles

IF EVERY METHOD measures SAME WIMP mass, then PERFECT.In this case Dark Matter is the supersymmetric partner of the CMB!

wim de boer, karlsruhe seminar beijing, august 15, 2007 1 dark matter visible by hard gamma rays?...

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