dept. of physics /lbnl uc berkeley uc institute for …...slac summer institute 11 august 2009 1...
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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
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B.SadouletSlac Summer Institute 11 August 2009
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.
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B.SadouletSlac Summer Institute 11 August 2009
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
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Strategies
Highly iterative
B.SadouletSlac Summer Institute 11 August 2009 5
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
B.SadouletSlac Summer Institute 11 August 2009
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
1.Input from Cosmology and Particles Physics2. Axions3. WIMPS: Framework4. WIMPs: Current status
B.SadouletSlac Summer Institute 11 August 2009
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
B.SadouletSlac Summer Institute 11 August 2009
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
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1.Input from Cosmology and Particles Physics2. Axions3. WIMPS: Framework4. WIMPs: Current status
B.SadouletSlac Summer Institute 11 August 2009 9
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
1.Input from Cosmology and Particles Physics2. Axions3. WIMPS: Framework4. WIMPs: Current status
B.SadouletSlac Summer Institute 11 August 2009
Variety of candidates
L. Roszkowski
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1.Input from Cosmology and Particles Physics2. Axions3. WIMPS: Framework4. WIMPs: Current status
B.SadouletSlac Summer Institute 11 August 2009 11
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
B.SadouletSlac Summer Institute 11 August 2009
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
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1. Input from Cosmology and Particles Physics2. Axions3. WIMPS: Framework4. WIMPs: Current status
B.SadouletSlac Summer Institute 11 August 2009
Galactic Axion
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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!
1. Input from Cosmology and Particles Physics2. Axions3. WIMPS: Framework4. WIMPs: Current status
B.SadouletSlac Summer Institute 11 August 2009
Solar Axions
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Emitted by SunConvert in a magnet : Helioscope: Tokyo, CASTCrystal: Bragg condition
1. Input from Cosmology and Particles Physics2. Axions3. WIMPS: Framework4. WIMPs: Current status
Make you own GAMEV (Fermilab)Pay the price of g4
B.SadouletSlac Summer Institute 11 August 2009 15
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
1. Input from Cosmology and Particles Physics2. Axions3. WIMPS: Framework4. WIMPs: Current status
B.SadouletSlac Summer Institute 11 August 2009
3 Complementary ApproachesCDMS
WIMP scattering on Earth:e.g. CDMS : currently leading the field
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Halo made of WIMPs1/2 shown for clarity
WIMP production on Earth
HESS
WIMP annihilation in the cosmos
GLAST
GLAST/FermiLaunched 11 June 2008
1. Input from Cosmology and Particles Physics2. Axions3. WIMPS: Framework4. WIMPs: Current status
B.SadouletSlac Summer Institute 11 August 2009
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
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1. Input from Cosmology and Particles Physics2. Axions3. WIMPS: Framework4. WIMPs: Current status
B.SadouletSlac Summer Institute 11 August 2009
Complementarity mSugra/CMSSM
Direct Detection: Bulk
+Focus point
LHC “low energy”
1 fb -1
Fermi Focus + Higgs funnel
100/pb
1. Input from Cosmology and Particles Physics2. Axions3. WIMPS: Framework4. WIMPs: Current status
Taking as a guide mSugra/Constrained Minimum SuperSymmetric model (4 parameters +1 sign)(but take with grain of salt!)
Take with grain of salt
B.SadouletSlac Summer Institute 11 August 2009 19
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
1. Input from Cosmology and Particles Physics2. Axions3. WIMPS: Framework4. WIMPs: Current status
B.SadouletSlac Summer Institute 11 August 2009
Elastic scattering
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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
B.SadouletSlac Summer Institute 11 August 2009 21
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
1. Input from Cosmology and Particles Physics2. Axions3. WIMPS: Framework4. WIMPs: Current status
B.SadouletSlac Summer Institute 11 August 2009 22
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)
1. Input from Cosmology and Particles Physics2. Axions3. WIMPS: Framework4. WIMPs: Current status
B.SadouletSlac Summer Institute 11 August 2009
Challenges
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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
1. Input from Cosmology and Particles Physics2. Axions3. WIMPS: Framework4. WIMPs: Current status
B.SadouletSlac Summer Institute 11 August 2009
Experimental Approaches
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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
B.SadouletSlac Summer Institute 11 August 2009 25
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
1. Input from Cosmology and Particles Physics2. Axions3. WIMPS: Framework4. WIMPs: Current status
B.SadouletSlac Summer Institute 11 August 2009 26
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)
1. Input from Cosmology and Particles Physics2. Axions3. WIMPS: Framework4. WIMPs: Current status
B.SadouletSlac Summer Institute 11 August 2009 27
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
1. Input from Cosmology and Particles Physics2. Axions3. WIMPS: Framework4. WIMPs: Current status
Taking again as a guide mSugra/Constrained Minimum SuperSymmetric model (but take with even more a grain of salt than spin independent!)
B.SadouletSlac Summer Institute 11 August 2009
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
1. Input from Cosmology and Particles Physics2. Axions3. WIMPS: Framework4. WIMPs: Current status
B.SadouletSlac Summer Institute 11 August 2009
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
1. Input from Cosmology and Particles Physics2. Axions3. WIMPS: Framework4. WIMPs: Current status
B.SadouletSlac Summer Institute 11 August 2009
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
1. Input from Cosmology and Particles Physics2. Axions3. WIMPS: Framework4. WIMPs: Current status
B.SadouletSlac Summer Institute 11 August 2009
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
1. Input from Cosmology and Particles Physics2. Axions3. WIMPS: Framework4. WIMPs: Current status
B.SadouletSlac Summer Institute 11 August 2009
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
1. Input from Cosmology and Particles Physics2. Axions3. WIMPS: Framework4. WIMPs: Current status
B.SadouletSlac Summer Institute 11 August 2009
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!
1. Input from Cosmology and Particles Physics2. Axions3. WIMPS: Framework4. WIMPs: Current status