dept. of physics /lbnl uc berkeley uc institute for …...slac summer institute 11 august 2009 1...

B.SadouletSlac Summer Institute 11 August 2009 1

Direct Dark Matter SearchesElements of a Strategy

Bernard SadouletDept. of Physics /LBNL UC BerkeleyUC Institute for Nuclear and ParticleAstrophysics and Cosmology (INPAC)

Inputs from Cosmology and Particle PhysicsNon baryonic cold dark matterAxions: a dynamic way to restore CP invarianceWIMPs: a generic consequence of new physics at TeV scale

AxionsWIMPs

We need three approaches: accelerators, direct detection and indirect detectionThe direct detection challenges

Current statusResultsDAMA: tension with other experiments

B.SadouletSlac Summer Institute 11 August 2009

Tomorrow

The road to larger massComparison of the various technologies Importance of discrimination/ fiducial volume => zero background

Need for directional detectorsChallenges

A roadmap for the future2 phases: Next 5 years exploration of technology+ push science frontier

By 2014 converge on 2 technologies (maybe 3 world wide) +directional detector as soon as we have a discovery

2


Relationship with other talks

Complementary toTalk this afternoon by Gabriella Sciolla:

She will focus on individual experiments and their current resultsI will focus on the overall picture, providing today background to her talk and elaborating on

the overall strategy of the field tomorrow.Lectures by Max Tegmark Neil Weiner Jan Conrad

Even if there is overlap, the differences in perspective may be interesting.

3


What generic class(es) to look for?Fundamental Physics

in particular ≥ 2 justificationsexperimental consequences

What approach?Privilege unambiguous information

minimize “gastrophysics”Complementary approaches

e.g. Direct detection Indirect detection Colliders

What sensitivity goals?Identify natural scale

+ fine tuningPrevious results

Cross checks

What technology?Highly discriminativeLarge amount of information: rare events ≠ pathological configurationIdentification of background

4

Strategies

Highly iterative


Standard Model of Cosmology

Ωm >>Ωb = 0.047 ± 0.006 fromNucleosynthesis

WMAP

Not ordinary matter (Baryons)

+ internally to WMAP Ωmh2 ≠ Ωbh

2 ≈15 σ's

Mostly cold: Not light neutrinos≠ small scale structure

χ

1.Input from Cosmology and Particles Physics2. Axions3. WIMPS: Framework4. WIMPs: Current status

Ωmatter

A surprising but consistent picture

NASA/WMAP Science Team 2006

ΩΛ


Dark Matter is cold

6

Tegmark,Zeldarriaga Astro-ph/0207047baryonicNeutrinos

“Cold”Non relativistic when comes out of the horizon ≡ time of galaxy formation

≠ light neutrinos =”Hot”erase density fluctuations at small

scale

Recurrent appeal to warm dark matter

or “mixed” (Cold +hot)to soften spectrumSeverely limited by Lyman alphasystems



Large Scale Structure

7

Great increase in numerical accuracy

1010 particles

e.g.Halo substructure and merging history

Hydrodynamics (although still course feedback mechanisms)

Non baryonic dark matter is an essential ingredient of our understanding of structure formation

Galaxy scale: disk + haloIntermediate scale: hierarchical mergingPower spectrum

Amazing first approximation

HST Ultra Deep Field

c1.Input from Cosmology and Particles Physics2. Axions3. WIMPS: Framework4. WIMPs: Current status


Challenges

Too peaked a distribution in center of galaxies“Cusp problem” :Navaro-Frenk-White profile density ≈r-1

Dwarf spheroidals : mostly underestimate of beam smearingLow surface brightness galaxies (Blitz); when no radial motion ≈r-1

Non-circular motions could be caused by nonspherical halos (Navarro & Hayashi).Large galaxies?

Halo substructure <=Merging histories“missing satellites” Problems with simulatiion: e.g. Loss of gas => agreement with data.

Angular momentum problem Catastrophic loss of angular momentum in current hydrodynamics simulations => difficulty to form spiral galaxies

Formation and role of AGN? A long history of overcoming challenges

8



Standard Model of Particle Physics

Fantastic success butModel is unstable

Why is W and Z at ≈100 Mp? Need for new physics at that scale supersymmetry additional dimensions

Flat: Cheng et al. PR 66 (2002) Warped: K.Agashe, G.Servant hep-ph/0403143

In order to prevent the proton to decay, a new quantum number => Stable particles: Neutralino Lowest Kaluza Klein excitation

QCD violates CPDynamic stabilization by a Peccei-Quinn axion?

Gravity is not included and we do not understand vacuum energy

Always the danger of a failure of General Relativityand that dark matter is part of a new set of “epicycles” that we invent to

adjust theory to increasingly accurate data



Variety of candidates

L. Roszkowski

10



Axions

Method of detection

Tunable cavity: Most suitable for low mass region

ma = 0.62eV107GeV

fa

⎛⎝⎜

⎞⎠⎟

Laγγ =α em

2π fa

⎛⎝⎜

⎞⎠⎟E.B ×O 1( )

1. Input from Cosmology and Particles Physics2. Axions3. WIMPS: Framework4. WIMPs: Current status

Invented to save QCD from strong CP violation Current experimental limits are such that if they exist,

they have to be cosmologically significant Window: 10-6-10-3 eV

Produced out of equilibriumTheoretical discussion if Peccei Quinnn symmetry breaking occurs after

inflation => global strings which radiate axions. Technically difficult to compute

(Shellard≠Sikivie) Loss mass region may be not favored


Axions

Microwave technologyReaching cosmologically interesting rangeWith new SQUID microstrip amplifier (nearly quantum limited) -> lowest

range of couplingADMX will cover lowest decade of 3 decades still open

12



Galactic Axion

13

arXiv:0902.4693

Assumes that σ ≠

Av

DAMA: An axionic type particle of 3 keV converting its mass into electromagnetic energy in detector

Modulation by fluxCan be in principle checked by other detectors: being done by CDMS+

CoGeNT!



Solar Axions

14

Emitted by SunConvert in a magnet : Helioscope: Tokyo, CASTCrystal: Bragg condition


Make you own GAMEV (Fermilab)Pay the price of g4


Particles in thermal equilibrium + decoupling when nonrelativistic

Cosmology points to W&Z scaleInversely standard particle model requires new physics at this scale (e.g. supersymmetry or additional dimensions) => significant amount of dark matter

Weakly Interacting Massive Particles

Freeze out when annihilation rate ≈ expansion rate

⇒Ωxh2 =

3 ⋅10-27cm3 / sσ Av

⇒σ A ≈α 2

MEW

2 Generic Class

WIMPsBringing both fields together: a remarkable concidence

2 generic methods: Direct Detection= elastic scattering

Indirect: Annihilation products γ ’s e.g. 2 γ ’s at E=M is the cleanest ν from sun &earth ≈ elastic scattering dependent on trapping time+ Large Hadron Collider

e+ , p



3 Complementary ApproachesCDMS

WIMP scattering on Earth:e.g. CDMS : currently leading the field

16

Halo made of WIMPs1/2 shown for clarity

WIMP production on Earth

HESS

WIMP annihilation in the cosmos

GLAST

GLAST/FermiLaunched 11 June 2008



We need all three approaches

Direct detectionMay well provide a detection + ≈ cross section and massBut what is the fundamental physics behind it?What can we learn about the galaxy?

LHCMay well give rapidly evidence for new physics: missing energyBut is it stable? => need direct or indirect detectionAmbiguity in parameters: mass/cross section

Indirect detectionMay well provide smoking gun for both dark matter and hierarchical

structure formation (subhalos)But possible ambiguity in interpretation => need direct detection

Complementary sensitivity to different parameter space region

17



Complementarity mSugra/CMSSM

Direct Detection: Bulk

+Focus point

LHC “low energy”

1 fb -1

Fermi Focus + Higgs funnel

100/pb


Taking as a guide mSugra/Constrained Minimum SuperSymmetric model (4 parameters +1 sign)(but take with grain of salt!)

Take with grain of salt


Elastic Scattering Rates

where

σ o=dσ q = 0( )d q 2( )0

4mr2v2

∫ d q 2( ) = independent of v

ρo = local density of halo

vmin =EdmN

2mr2

⎛⎝⎜

⎞⎠⎟

2

ve = vo 1.05 + 0.07 cos2π t − 2ndJune( )

1yr⎛⎝⎜

⎞⎠⎟

⎡

⎣⎢

⎤

⎦⎥

Annual modulation ±4.5%

If Maxwellian in galaxy rest frame

f v'( )d3v' =1

vo3π 3 / 2 exp −

v' 2

vo2

⎛ ⎝ ⎜ ⎞

⎠ ⎟ d3v'

differential rate per unit mass

dRdEd

=σ oρo

4vemχmr2 F

2 q( ) erf vmin + vevo

⎛ ⎝ ⎜ ⎞

⎠ ⎟ − erf vmin − ve

vo

⎛ ⎝ ⎜ ⎞

⎠ ⎟ ⎡

⎣ ⎢ ⎤

⎦ ⎥

Convolution with velocity distribution in the halo

Energy deposition cf J.D Lewin and P.F. Smith AstroPart. Phys. 6(1996) 87Simple non relativistic calculation

Ed

dRdEd

Ed =q2

2mN

=mχ2mN

mχ + mN( )2v2 1− cosθ *( ) = mr

2

mN

v2 1− cosθ *( )

s-wave scattering:

for given velocity v, flat between 0 and Edmax =2mr

2

mN

v2



Elastic scattering

20

Difference between electron and nucleus recoil energy deposition

True for ionization and scintillationLittle effect on phonons (measure total energy)

Nearly ExponentialContinuous full calculationDotted=exponential

0 10 20 30 40 50 60 70 80 90 10010

!6

10!5

10!4

10!3

10!2

10!1

100

Recoil energy (keV)

dsig

ma

/dE

r

WIMP spectra

10

20

30

50

60

100

200

300

1e+03

1e+04

Ge MWIMP= GeV/c2


Coherent Scattering

• “Spin dependent” : additive quantum number is spin First order interaction of Majorana spin 1/2 particle is axial vector -> spin at

low energy depends on spin content of the nucleus (Most nuclei spinless) Spin is never very large: usually <2nd order Uncertainties on spin content of nucleon + “Peripheral” form factor

The energy transfer is small compared to inverse size of nucleus

Conventionally • “Spin independent” : additive quantum number is mass, number of protons or neutrons! Usually scalar interaction dominates Cross sections≈A2

+ “filled sphere” form factor



Direct Detection dn/dEr

Er

Expected recoil spectrum

Elastic scatteringExpected event rates are low (<< radioactive background)Small energy deposition (≈ few keV) << typical in particle physics

Signal = nuclear recoil (electrons too low in energy) ≠ Background = electron recoil (if no neutrons)

Signatures• Nuclear recoil• Single scatter ≠ neutrons/gammas• Uniform in detector

Linked to galaxy• Annual modulation (but need several thousand events)• Directionality (diurnal rotation in laboratory but 100 Å in solids)



Challenges

23

log(exposure=target mass M × time T)

log

sens

itiv

ity

sensitivity ∝MT

sensitivity ∝MT

sensitivity ∝ constant

Three General Challenges• Understand/Calibrate detectors• Be background free

much more sensitive than background subtraction (eventually limited by systematics)

• Increase mass while staying background free



Experimental Approaches

24

CRESST I

CDMS

EDELWEISS

CRESST II

ROSEBUD

ZEPLIN II, III

XENON

WARP

ArDM

SIGN

NAIAD

ZEPLIN I

DAMA

XMASS

DEAP

Mini-CLEAN

DRIFT

IGEX

COUPP

Scin

tillatio

n

Heat -

Phonons

Ionization

Direct Detection Techniques

Ge, Si

Al2O3, LiF

!"#$%&'()$

*+#$%&',-.$/ 0

NaI, Xe,

Ar, Ne

Xe, Ar,

Ne

Ge, CS2, C3F8

~100%

of

En

erg

y

~20% of Energy

Few

% o

f Energ

y

At least two pieces of information in order torecognize nuclear recoilextract rare events from background (self consistency)+ fiducial cuts (self shielding, bad regions)

A blooming field

As large an amount of information and a signal to noise ratio as possible

1. Particle Cosmology and WIMPs2. WIMPs: current status3. The road to high target mass


Detection TechniquesMethod Detection Electron recoil Nuclear recoil Discrimination Groups

Scintillation e.g. NaI Light ≈200eV/ photoelectron

I: ≈1600eV/ photoelectron

Pulse shape DAMA, UK NaI, Elegant

Germanium @liquid nitrogen

Electrons + holes 3eV/carrier 9eV/carrier No Heidelberg-Moscow

Gas Ionization electrons 20eV/electron 60eV/electron Track Length DRIFT/MIMAC Cygnus /DMTPC

High pressure gas electrons+light 20eV/electron 60eV/electron Ionization+Scintillation

UCLA/Texas

Liquid Xe Scintillation Light ≈200eV/photo electron

≈1600eV/photo electron

Pulse shape 4ns/22ns

Rome, ZEPLIN I, XMASS

Liquid Xe Ionization+ Scintillation

electrons 15eV/electron≈200eV/p.e.

45eV/electron≈1600eV/p.e.

Ionization Yield Pulse shape

ZEPLIN II-II-IVXENON

Liquid Ar Scintillation Light 500eV/p.e. 600-2000 eV/p.e ? Pulse shape 6ns/1.6µs

MiniClean Deap Clean

Liquid Ar Ionization+ Scintillation

electrons 20eV/electron500eV/p.e.

60eV/electron600-2000 eV/p.e ?

Ionization YieldPulse shape

WArp ARP

Phonon mediated phonons 100µeV/phonon 100µeV/phonon No Cuerocino (2β) CRESST I

Ionization/phonons @ low temperature

Electrons + holesPhonons

3eV/carrier 100µeV/phonon

9eV/carrier 100µeV/phonon

Ionization yield Phonon timing/shape

CDMS,SCDMS Edelweiss

Scintillation/phonons @ low temperature

LightPhonons

100eV/ photoelectron on O 900eV/ photoelectron

Scintillation yieldat least on O

CRESST II

Superheated Droplets Sound not sensitive 10keV-100keV tunable

energy densitysensitive to alphas

Simple Picasso

Bubble chamber CCD camera not sensitive 10keV-100keV tunable

energy densitysensitive to alphas

COUPP



Natural scale? 10-45 cm2

χ20 , χ1

±

Coannihilation

Bulk(5 < tan β < 45)

Focus Point (tan β~10)

Stau Coannihilation (tan β ~ 10)

Higgs Funnel (50 < tan β < 60)

Low cross sections correspond to fine tuningThe Higgs funnel and stau coannihilation are fine tuned to enhance annihilationThe lower the elastic cross section, the finer the tuning!

10-45cm2 is a natural scaleBulk (LSP= pure Bino: Higgs dominant) Focus region /split supersymmetry (LSP higgsino component: high annihilation+ elastic σ)



Spin Dependent?

Two complementary approaches

Spin independent experiments

Spin dependent but have to get fromcurrent 10-37 to 10-42 cm2

≈ 50-500 kg COUPP

Roughly proportionalSpin dependent ≈1000x spin independent

But no A2 enhancement factor


Taking again as a guide mSugra/Constrained Minimum SuperSymmetric model (but take with even more a grain of salt than spin independent!)


Where are we? January 09

28

Scalar couplings: Spin independent cross sectionslatest compilation by Jeff FilippiniGray=DAMA 2 regions(Na, I) from Savage et al.

WIMP mass [GeV/c2]

WIM

P−nu

cleo

n σ SI

[cm

2 ]

101 102 10310−44

10−43

10−42

10−41

10−40

Ellis 2005 LEESTRoszkowski 2007 (95%)Roszkowski 2007 (68%)DAMA/LIBRA 2008EDELWEISS 2005

WARP 2006ZEPLIN III 2008XENON10 2007CDMS all SiCDMS all Ge



Where are we? January 2009

29

Spin dependent couplings

ap vs an at mass of 60GeV/c2

WIMP mass [GeV/c2]

WIM

P−pr

oton

σSD

[cm

2 ]

101 102 10310−41

10−40

10−39

10−38

10−37

10−36

10−35

10−34

Roszkowski 2007 (95%)Roszkowski 2007 (68%)DAMA/LIBRA 2008COUPP 2008KIMS 2006XENON10 2007SuperK 2004CDMS all Ge

WIMP mass [GeV/c2]

WIM

P−ne

utro

n σ SD

[cm

2 ]

101 102 10310−41

10−40

10−39

10−38

10−37

10−36

10−35

10−34

Roszkowski 2007 (95%)Roszkowski 2007 (68%)DAMA/LIBRA 2008XENON10 2007CDMS all SiCDMS all Ge

an

a p

−2 −1 0 1 2−4

−3

−2

−1

0

1

2

3

4

DAMA/LIBRA 2008KIMS 2006XENON10 2007SuperK 2004CDMS all Ge



Claim of DAMA/LIBRA 08

30

E

Dec 2

dNdE

June 2

If WIMPs exist, we expect a modulation in event rate

SunEarth

≈5.5%Clearly a modulation

Not a WIMP: incompatible with other experiments

DAMA claims 3 keV peak cannot be fully explained by 40K escape peak



Tension with Other Expts.

31

Spin independent interactions

WIMP mass [GeV/c2]

WIM

P−nu

cleo

n σ SI

[cm

2 ]

101 102 10310−44

10−43

10−42

10−41

10−40

Ellis 2005 LEESTRoszkowski 2007 (95%)Roszkowski 2007 (68%)DAMA/LIBRA 2008EDELWEISS 2005

WARP 2006ZEPLIN III 2008XENON10 2007CDMS all SiCDMS all Ge

DAMA

Spin dependent

WIMP mass [GeV/c2]

WIM

P−pr

oton

σSD

[cm

2 ]

101 102 10310−41

10−40

10−39

10−38

10−37

10−36

10−35

10−34

Roszkowski 2007 (95%)Roszkowski 2007 (68%)DAMA/LIBRA 2008COUPP 2008KIMS 2006XENON10 2007SuperK 2004CDMS all Ge

WIMP mass [GeV/c2]

WIM

P−ne

utro

n σ SD

[cm

2 ]

101 102 10310−41

10−40

10−39

10−38

10−37

10−36

10−35

10−34

Roszkowski 2007 (95%)Roszkowski 2007 (68%)DAMA/LIBRA 2008XENON10 2007CDMS all SiCDMS all Ge

DAMA



What could it be: Physics?

32

An axionic type particle of 3 keV converting its mass into electromagnetic energy in detector

Modulation by flux Electron recoil line at 3 keVChecked by other detectors: CoGeNT, CDMS!

3 keV peak excluded cf. CDMS arXiv:0907.1438 3 keV peak in DAMA single rate is not physical (if Z2 scaling)

Probably 40K escape (1.46MeV missed)Excludes as modulation signal as big as DAMA (even in optimistic case of ±6%)

Note that cross sections of exothermic radiations tend to be inversely proportional to velocity => modulation very much suppressed (Pospelov et al. 2008)

Unmodulated rate

modulated rate ±6%

55Fe

Ga



What could it be?

33

Sociological problem:Nobody finds the result plausible enough to repeat the experiment!However, as a field we need to cross check the only claim.

A different team has to redo the experiment in Southern Hemisphere

e.g. NaI detectors in a hole in Antarctic Ice (Stubbs, Fisher, IceCube, B.S.)

Most likely very subtle detector problemModulation is basically summer-winterExample of the cosmic muon rate which is modulated with the same phase (decay path of

the pions change with temperature)Many things change: temperature, water in mountain, humidity, electric voltage

What seems excludedNeutron from muonsDirect effect of muons on detector

Examples of effects which have not been excluded convincinglyModulation of the efficiency

e.g. of the PM noise rejection algorithmModulation of the 40K 1.46 MeV gamma detection efficiency

(e.g. varying humidity in purge gas=> modulation of dead layer=> 3 keV escape)

Not blind analysis!


dept. of physics /lbnl uc berkeley uc institute for …...slac summer institute 11 august 2009 1...

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