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