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The Experimental Search for Direct Dark Matter
Cristiano Galbiati Princeton University Scuola di Otranto
June 6, 2015
Has gravitational interactions
Is long lived
Is cold
Is not baryonic
Feng
Dark Matter• Best evidence for new physics beyond Standard Model
• Unambiguous evidence
• Possibly connected with electroweak symmetry breaking, SUSY, and structure formation
• Very bright prospects for experimental observation
• Astroparticle physics: direct and indirect searches
• Particle physics: CMS and ATLAS at LHC
• Cosmology: halo profiles, CMB, BBN
e,γχ,n
Attisha
1 10 100 1000 10410!5010!4910!4810!4710!4610!4510!4410!4310!4210!4110!4010!39
10!1410!1310!1210!1110!1010!910!810!710!610!510!410!3
WIMP Mass !GeV"c2#
WIMP!nucleoncrosssection!cm2 #
WIMP!nucleoncrosssection!pb#
(Green&ovals)&Asymmetric&DM&&(Violet&oval)&Magne7c&DM&(Blue&oval)&Extra&dimensions&&(Red&circle)&SUSY&MSSM&&&&&&MSSM:&Pure&Higgsino&&&&&&&MSSM:&A&funnel&&&&&&MSSM:&BinoEstop&coannihila7on&&&&&&MSSM:&BinoEsquark&coannihila7on&&
8BNeutrinos
Atmospheric and DSNB Neutrinos
CDMS II Ge (2009)
Xenon100 (2012)
CRESST
CoGeNT(2012)
CDMS Si(2013)
EDELWEISS (2011)
DAMA SIMPLE (2012)
ZEPLIN-III (2012)COUPP (2012)
SuperCDMS Soudan Low ThresholdXENON 10 S2 (2013)
CDMS-II Ge Low Threshold (2011)
SuperCDMS Soudan
Xenon1T
LZ
LUX (2013)
DarkSide G2
DarkSide 50
DEAP3600
PICO250-CF3I
PICO250-C3F8
SNOLAB
SuperCDMS
7BeNeutrinos
NEUTRINO C OHER ENT SCATTERING
NEUTRINO COHERENT SCATTERING
CDMSlite
(2013)
SuperCDMS SNOLAB
Z-mediated scattering
H-mediated scattering
Figueroa-Feliciano
(1)
(2)
(3)
R. Kolb and M. TurnerNon-baryonic Not hot
Not short lived
(1) Equilibrium
(2) Eq. Cooling
(3) Freeze-out
��� f̄f
��� f̄f
�� � f̄f
dn�
dt+ 3Hn� = �⇥�Av⇤
⇤(n�)2 �
�neq
�
⇥2⌅
The WIMP MiracleDark matter “leftovers” inversely proportional
to annihilation cross section
��h2 =m�n�
�c=
3 � 10�27 cm3/s⇥⇥Av⇤freezout
⇥�Av⇤freezout = 3 � 10�26 cm3/s
⇥⇥Av⇤ � �2 (100 GeV)�2 � 10�25 cm3/s
Cosmology alone tells us to look at the weak scale!
For weak scale particles:
Feng
The 1985 Papers
• Drukier and Stodolski, Phys Rev D 30, 2295 (1985)
• Goodman and Witten, Phys Rev D 31, 3059 (1985)
WIMP Scattering: Coherence
Halo particle of mass m (100 GeV) velocity v=300 km/s
on nucleus of mass M (100 GeV)
λ = h/(2mv) ≈ 1 fm RA = 1.0 x A1/3 fm
K = (2mv)2/2M ≈ 100 keV
WIMP Coherent Scattering
�0 = ��,nA2 µ2A
µ2n
µA =MAM�
MA + M�
µn =mnM�
mn + M�
q =�
(2MAE)
F (q) =3j1(qrn)
qrne�q2s2/2
�(q) = �0F2(q)
Reduced Mass WIMP-Nuclide:
Reduced Mass WIMP-Nucleon:
Momentum transferred:
Form Factor:
For zero momentum transfer:
Non-null momentum transfer:
Dark Matter Signatures
0.2
0.4
0.6
0.8
1
200 100806040 200 100806040 200 100806040
1x10-2
1x10-3
1x10-4
1x10-5
1x10-1
10.5
0.05
0.01
0.005
0.1
Recoil Energy E [keV]R
Form Factor (Square of) Integral Rate over ThresholdDifferential Rate
Ev/kg/keV/d
Ev/kg/d
ArAr
ArGe
GeGe
XeXe Xe
(a) (b) (c)
Rate per unit mass depends on atomic number A Nuclear recoils spectrum depends on atomic number A
Yearly modulation of spectrum Daily modulation of nuclear recoil directionality
WIMP Wind & Signatures
WIMP “wind”
in the summer, moving against wind
in the winter, moving away from wind
expect an annual modulation in signal!
Drukier-Freese-Spergel
Status of Experimental Exploration• One unconfirmed result from DAMA
• strong statistical significance, 8σ
• Standard WIMP elastic scattering ruled out by Ar, Ge, and Xe
• Two powerful techniques lined up long range searches in the standard WIMP scenario
• Ge, Xe, and Ar
DAMA Singles Spectrum: Peak at 3±1 keV
Intensity 1 cpd/kg
2-6 keV
Time (day)
Res
idua
ls (c
pd/k
g/ke
V) DAMA/NaI (0.29 ton yr)
(target mass = 87.3 kg)DAMA/LIBRA (0.53 ton yr)
(target mass = 232.8 kg)
0
2
4
6
8
10
2 4 6 8 10 Energy (keV)
Rat
e (c
pd/k
g/ke
V)
2-6 keV
Time (day)
Res
idua
ls (c
pd/k
g/ke
V) DAMA/NaI (0.29 ton yr)
(target mass = 87.3 kg)DAMA/LIBRA (0.53 ton yr)
(target mass = 232.8 kg)
Energy (keV)
S m (c
pd/k
g/ke
V)
-0.05
-0.025
0
0.025
0.05
0 2 4 6 8 10 12 14 16 18 20
DAMA Oscillated Spectrum: Peak at 3±1 keV, Intensity 0.05 cpd/kg
0
5
10
15
20
25
30
35
40
45
0 1000 2000 3000 4000
TD channel
Counts/bin
DAMA Concidence Spectrum:
Peak at 3±1 keV Intensity 10,000 cpd!!! Origin: 3.2 keV X-rays from 40Ar, produced by
decay of 40K (13 ppb of natK)
1 10 100 1000 10410!5010!4910!4810!4710!4610!4510!4410!4310!4210!4110!4010!39
10!1410!1310!1210!1110!1010!910!810!710!610!510!410!3
WIMP Mass !GeV"c2#
WIMP!nucleoncrosssection!cm2 #
WIMP!nucleoncrosssection!pb#
(Green&ovals)&Asymmetric&DM&&(Violet&oval)&Magne7c&DM&(Blue&oval)&Extra&dimensions&&(Red&circle)&SUSY&MSSM&&&&&&MSSM:&Pure&Higgsino&&&&&&&MSSM:&A&funnel&&&&&&MSSM:&BinoEstop&coannihila7on&&&&&&MSSM:&BinoEsquark&coannihila7on&&
8BNeutrinos
Atmospheric and DSNB Neutrinos
CDMS II Ge (2009)
Xenon100 (2012)
CRESST
CoGeNT(2012)
CDMS Si(2013)
EDELWEISS (2011)
DAMA SIMPLE (2012)
ZEPLIN-III (2012)COUPP (2012)
SuperCDMS Soudan Low ThresholdXENON 10 S2 (2013)
CDMS-II Ge Low Threshold (2011)
SuperCDMS Soudan
Xenon1T
LZ
LUX (2013)
DarkSide G2
DarkSide 50
DEAP3600
PICO250-CF3I
PICO250-C3F8
SNOLAB
SuperCDMS
7BeNeutrinos
NEUTRINO C OHER ENT SCATTERING
NEUTRINO COHERENT SCATTERING
CDMSlite
(2013)
SuperCDMS SNOLAB
Figueroa-Feliciano
0 10 20 30 40 501
1.2
1.4
1.6
1.8
2
2.2
2.4
2.6
log 10
(S2 b/S
1) x
,y,z
cor
rect
ed
S1 x,y,z corrected (phe)
3 6 9 12 15 18 21 24 27 30 keVnr
1.3
1.8
3.5
4.65.9
7.1
keVee
S1 [PE]100 150 200 250 300 350 400 450
90f
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
0
5000
10000
15000
20000
25000
30000
35000
50% 65% 80% 90%
1,422 kg×day - zero background - S1 only
S1 [PE]
100 150 200 250 300 350 400 450
90
f
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1Ar Residuals Box
39Dark Matter Search - S2 and Radial Cut - 0.1
0
500
1000
1500
2000
2500
3000
3500
4000
4500
50%65%
80% 90%
Ar Residuals Box39
Dark Matter Search - S2 and Radial Cut - 0.1 same data with S2 and radial cut
]2 [GeV/cχM1 10 210 310 410
]2 [cm
σ
50−10
49−10
48−10
47−10
46−10
45−10
44−10
43−10
42−10
41−10
40−10
DS-50 (2014)
WARP (2007)
LUX (2013)
XENON-100 (2
012)
CDMS (2010)
PandaX-I (20
14)
Neutrino Limit
third best dark matter limit at high masses
LHC@14 TeV
1 eventfrom neutrino-induced
nuclear recoil
DarkSide A Scalable Zero-Background Program• Pulse shape of scintillation provides powerful discrimination for NR
vs. EM events Rejection factor ~107 at 36 keVr threshold
• Ionization:scintillation ratio a semi-independent discrimination mechanismGreat spatial resolution from ionization drift localizes events, allowing rejection of multiple interactions, "wall events", etc.
• Underground argon39Ar abatement factor ≥150
Multi-Stage Program at LNGS
DarkSide-10Prototype detector
Future multi-ton detector
DarkSide-50 First physics detector
Discrimination
Beta/Gamma Nuclear Recoil
Liquid Argon TPC & Cryostat
4-m Diameter Liquid Scintillator
Neutron Veto
10-m high 11-m Diameter
Water Tank
DarkSide-50
Liquid Argon TPC
Liquid scintillator neutron veto
Water Cherenkov muon veto
Radon-suppressed assembly clean room
Two-Phase Argon TPC
PMTs
Liquid Argon Target
Field cage
Gaseous Argon layer
7Li(p,n) on thin LiF target to generate low
energy, pulsed, monochromatic neutron beam
Triple coincidence between pulse proton beam, LAr TPC, liquid scintillator detectors
for detection of scattered neutrons
SCENE
SCENE
Recoil Energy [keV]10 20 30 40 50 60
Kr(0V/cm)
83m
S1 Relative to
0.14
0.16
0.18
0.2
0.22
0.24
0.26
0.28
0.3
0.32
0 V/cm
100 V/cm
200 V/cm
300 V/cm
1000 V/cm
SCENE
Recoil energy [keV]10 20 30 40 50 60
S2 yield [PE/keV]
2
4
6
8
10
12
14
1650 V/cm
100 V/cm
200 V/cm
300 V/cm
500 V/cm
/keV]
-S2 yield [e
1
2
3
4
5
SCENE
Drift electric field [V/cm]0 200 400 600 800 1000
S1 yield relative to 0 field
0.7
0.75
0.8
0.85
0.9
0.95
1
1.05
1.1
1.15 57.2 keV
dεParallel to
dεPerpendicular to
Class 100 Clean Room Radon < 5mBq/m3
S1 [PE]0 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000
s]
× kg
×Events/[50 PE
7−10
6−10
5−10
4−10
3−10
2−10
1−10AAr (200 V/cm, 44 kg)
S1 [PE]0 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000
s]
× kg
×Events/[50 PE
7−10
6−10
5−10
4−10
3−10
2−10
1−10AAr (200 V/cm, 44 kg)
UAr (200 V/cm, 44 kg)
AAr (200 V/cm, 44 kg)
UAr (200 V/cm, 44 kg)
S1 [PE]
0 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000
s]
× kg
×Events/[50 PE
7−10
6−10
5−10
4−10
3−10
2−10
1−10AAr (200 V/cm, 44 kg)
UAr (200 V/cm, 44 kg)
UAr (200 V/cm, 4 kg core)
AAr (200 V/cm, 44 kg)
UAr (200 V/cm, 44 kg)
UAr (200 V/cm, 4 kg core)
AAr (200 V/cm, 44 kg)
UAr (200 V/cm, 44 kg)
UAr (200 V/cm, 4 kg core)
DarkSide-50• Third best dark matter limit with AAr exposure of 1,422 kg×day
• Only liquid noble dark matter experiment background-free
• Rejection better than 1÷1.6×107 (compare 1÷200 for Xe)
• Detector in final configuration
• Underground argon isotopic depletion better than 300
• TMB problem fixed, veto at design 99.5% neutron rejection
• UAr science run started - additional exposure of 847 kg×day collected
What goal for the large scale exploration of dark matter?
]2 [GeV/cχM1 10 210 310 410
]2 [cm
σ
50−10
49−10
48−10
47−10
46−10
45−10
44−10
43−10
42−10
41−10
40−10
DS-50 (2014)
WARP (2007)
LUX (2013)
XENON-100 (2
012)
CDMS (2010)
PandaX-I (20
14)
Neutrino Limit
third best dark matter limit at high masses
LHC@14 TeV
1 eventfrom neutrino-induced
nuclear recoil
Experiment σ [cm2]@1 TeV/c2
σ [cm2]@10 TeV/c2
LUX[10k kg×day Xe]
1.1×10-44 1.2×10-43
XENON[7.6k kg×day Xe]
1.9×10-44 1.9×10-43
DS-50[1.4k kg×day Ar]
2.3×10-43 2.1×10-42
ArDM[1.5 tonne×yr Ar]
8×10-45 7×10-44
DEAP-3600[3.0 tonne×yr Ar]
5×10-46 5×10-45
XENON-1ton [2][2.7 tonne×yr Xe]
3×10-46 3×10-45
LZ [1][15 tonne×yr Xe]
5×10-47 5×10-46
DS-20k[100 tonne×yr]
9×10-48 9×10-47
1 Neutrino Event[400 tonne×yr Ar or 300 tonne×yr Xe]
2×10-48 2×10-47
ARGO[1,000 tonne×yr]
9×10-49 9×10-48
What are the backgrounds for large scale, high mass dark
matter searches?
Elastic scatters of pp solar neutrinos
Radioactive noble gases (39Ar)
Elastic Scatters of pp Solar Neutrinos on Electrons
• 200 events/tonne×yr in 30-200 keVnr ROI for argon means 80,000 background events @neutrino floor
• No problem due to β/γ rejection better than 1÷1.6×107
• 20 events/tonne×yr in 0-10 keVee ROI for xenon means 6,000 background events @neutrino floor
• Irreducible background due to rejection limited to 1÷200
39Ar Rejection1,422 kg×day (@AAr)
1 tonne×yr (UAr)
1,000 tonne×yr (UAr/DAr)
already achieved
stronger discrimination present value stat limited
additional active isotopic depletion
x 300 (39Ar AAr/39Ar UAr)
Based on what we know today, can a depleted argon experiment be background
free at the scale of 400 tonnes×yr?
Yes• pp neutrino-electron scattering
Not a concern thanks to pulse shape discrimination
• 214Pb from 222Rn and 85KrNot a concern thanks to pulse shape discrimination
• 39ArDiscrimination proven so far on exposure of 1 tonne×yr UAr equivalentNo deviations from statistical behavior of discrimination Current 1÷1.6×107 rejection limited by statistics SiPM should allow to increase light yield by ×1.5, which projects to more than 3 additional orders of magnitude in discrimination at the same threshold Further isotopic depletion of 39Ar available if required
Based on what we know today, can a xenon experiment be background free at the scale of 300 tonnes×yr?
No• [3] Next generation XENON-1t experiment need to contain their electron-recoil background
to below 30 μDRU for a 99.75% rejection to obtain 0.7 events in 2.7 tonne×yr exposure(1 DRU = 1 count / [keVee × kg × day])
• Is a 99.75% rejection reasonable?XENON-100 [2]: 2 leakage events over 400 in ROILUX [5]: 1 leakage events over 160 in ROI
• [3] pp neutrino-electron scattering: Irreducible background, 12 μDRU ≈ 0.3 (event/tonne×yr) • [3] 214Pb from 222Rn: 1mBq Rn ≈ 9 μDRU ≈ 0.2 (event/tonne×yr)
• Is 1 mBq of 222Rn reasonable? XENON-100: ≤ 1.2 mBq [2], ≃ 4 mBq [3] in 62 kg target for 222Rn chain; LUX [4]: 4-20 mBq in 350 kg target for 222Rn chain, 3 mBq for 220Rn chain222Rn background to scale with surface and recirculation flowBorexino’s success in 222Rn isolation, often invoked as a proof of principle for feasibility of Xe TPC goal, is taken out of context: Borexino’s 222Rn contamination during fluid operations: hundreds of mBq
• [3] 85Kr: 0.2 ppt ≈ 8 μDRU ≈ 0.2 (event/tonne×yr)
DarkSide-20k
• Background-free exposure of 100 tonne×yr
• Sensitivity 9×10-48 cm2 @1 TeV/cm2 A factor 5 better than LZ
• 30 tonne (20 tonne fiducial) detector
• MC indicates UAr self-vetoing sufficient (LS veto not required)
DarkSide-20k Characteristics• 15 m2 of SiPM’s
Demonstrated from 15 to 50% LY increase per unit area over PMT’s Demonstrated dark count under control Demonstrated noise control and good performance for 10 cm2 SiPM’s tile at 87 K Tile size required for DS-20k is 25 cm2 factor 2 above what already achieved FBK custom design, first custom production May 2015Mass production possibly at L-Foundry
• Low-background titanium from Russia for cryostat
• 50 kV drift fieldAlready achieved in DarkSide-10 and DarkSide-50 mockup
DarkSide Depleted Argon Sources• Urania
• expansion of Colorado UAr extraction facility to reach 100 kg/day
• Aria
• Giant cryogenic distillation column in Seruci, Sardinia
• Gas purification AND active isotopic depletion exploiting finite vapor pressure difference 39Ar/40Ar
What is Required?
• Upgrade of argon extraction at Cortez: 100 kg/day
• Distillation of Argon in Seruci, Sardinia, for further abatement of 39Ar
C.Kendziora 2.19.2015
Man
350 meters
325 meters Eiffel Tower
Seruci Distilation Column
Size ComparisonThe proposal is to construct a 350 meter talldistillation column at a mine called Suruci inSardina Italy to separate Argon 39 fromArgon 40.
DarkSide Depleted Argon Verification
• ~1 kg argon detector in a shallow underground location at Seruci for initial assessment39Ar sensitivity: 1 mBq/kg Factor 103 depletion (2-3 times better than DS-50)
• ArDM for high-sensitivity tests of tonne-scale batches 39Ar sensitivity: 10 μBq/kg Factor 105 depletion
Argo• Background-free exposure of 1,000 tonne×yr
• Sensitivity 9×10-49 cm2 @1 TeV/cm2Covers space throughout neutrino floor
• Permits precision measurements of solar neutrinos TPC affords very sharp definition of fiducial volume Argon ten times brighter than organic liquid scintillatorStatistical precision 2% for 7Be, 10% for pep, and 15% for CNO neutrinos Systematics under studyCosmogenics under control
• 300 tonne detectorRequires Borexino-style shield for solar neutrinos study
20- 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34
DS-20k
ARGO
7Li(p,n) on thin LiF target to generate low
energy, pulsed, monochromatic neutron beam
Triple coincidence between pulse proton beam, LAr TPC, liquid scintillator detectors
for detection of scattered neutrons
SCENE
SCENE
Recoil Energy [keV]10 20 30 40 50 60
Kr(0V/cm)
83m
S1 Relative to
0.14
0.16
0.18
0.2
0.22
0.24
0.26
0.28
0.3
0.32
0 V/cm
100 V/cm
200 V/cm
300 V/cm
1000 V/cm
SCENE
Recoil energy [keV]10 20 30 40 50 60
S2 yield [PE/keV]
2
4
6
8
10
12
14
1650 V/cm
100 V/cm
200 V/cm
300 V/cm
500 V/cm
/keV]
-S2 yield [e
1
2
3
4
5
SCENE
Drift electric field [V/cm]0 200 400 600 800 1000
S1 yield relative to 0 field
0.7
0.75
0.8
0.85
0.9
0.95
1
1.05
1.1
1.15 57.2 keV
dεParallel to
dεPerpendicular to
Directional Dark Matter Test @Napoli• Participating groups: Naples, Roma 1, APC-IN2P3, Princeton, Temple, UCLA
• Coordinator: Giuliana Fiorillo (Napoli)
• Refurbishment of Tandem accelerator to create dedicated proton line for experiment under way
• Permanent array of liquid scintillator neutron coincidence counters planned
• Start of operations with LAr TPC in October 2015
• Will provide facility available for calibration of other detectors with monochromatic, pulsed neutron beam
Very Low Threshold DM Searches• Gaseous argon detectors have reached record thresholds below 100 eV
• I. Giomataris et al., “A novel large-volume spherical detector with proportional amplification read-out”, Journal of Instrumentation 3, P09007 (2008).
• Availability of depleted argon made available by the Urania and Aria programs may enable construction of ultra-low background gaseous argon detectors
• Suitable to explore dark matter interactions on electrons
• Suitable to monitor supernovae explosions via the detection of neutrino-induced coherent scattering of argon nuclides
Conclusions• DS-20k most ambitious program proposed, goes more than ×5 beyond LZ
• Argo to cover entire parameter space through neutrino floor and to enable precision measurements of solar neutrinos significantly beyond Borexino capability
• Letter of Intent submitted to LNGS April 27 2015
• Background-free requirement key element continued excellence in dark matter exploration DS-20k and Argo have sound and credible strategy to keep background-free through their stated goals Unique physics capabilityReal competitor for large-scale background-free exploration of dark matter is single-phase argon (both approaches, TPC and single-phase argon, require UAr/DAr)INFN leading strategy procurement of depleted argon with Urania and Aria
• Exploration of possible directional signal continues with dedicated experiment at Naples Unique possibility of conjugating directionality with zero background strategy