pantic@ucdavis.edu 26

Emilija Pantic for the DarkSide collaboration

UC DAVIS

1

D A R K S I D E : C H A L L E N G E S , !P E R S P E C T I V E S A N D P L A N S

http://darkside.lngs.infn.it/collaboration

3rd Berkeley Workshop on the Direct Detection of Dark Matter

- DarkSide-50 brief intro and status!- DarkSide-20k CPP

Look for references here

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Pulse shape discrimination of ERsS2/S1 discrimination of ERs

DarkSide-50 LAr dual phase TPCLight Charge+

1

Edrift200V/cm

Eextr

e-e-

e-e-e-

e-

S2

S1

46kg of LAr!38 3” PMTs!TPB as wavelength shifter!cathode/anode = ITO on fused silica!Teflon as reflector !extraction grid

3D positioning O (few mm)

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

1

0

5000

10000

15000

20000

25000

30000

35000

50% 65%80% 90%

Nuclear Recoils

Electronic Recoils

ER Rejection power >107

First Results from the DarkSide-50 Dark Matter Experiment at LNGS, Phys.Lett. B 743

83mKr S1 Light Yield:!7.0 ± 0.3 PE/keV @ 200 V/cm

f90

f90 = fraction of S1 in the first 90ns

S1 [PE]

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prompt

WCV

LSV

3

DarkSide-50 Veto Detectors:

Neutrons that scatter in the TPC can be detected via capture signal on 10B or thermalization signal in LSV.

30t Liquid Scintillator Veto (LSV) = TMB + PPO + PC!1000t Water Cherenkov Veto (WCV)

Tag radiogenic n Tag radiogenic 𝛾 Tag cosmogenic n 𝜇

WCV

LSV

𝜋n

prompt

delayed

Water WCV

LSV

radi

opur

e

The veto system of the DarkSide-50 experiment, JINST 11, no.03, P03016 (2016)

>99.1% efficiency to veto radiogenic neutrons via delayed capture on 10B and 1H (AmBe + MC)

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S1 [PE]0 1000 2000 3000 4000 5000 6000

s]

× kg

×Events / [50 PE

8−10

7−10

6−10

5−10

4−10

3−10

2−10

1−10(LSV Anti-coinc.)AAr Data at 200 V/cm

(LSV Anti-coinc.)UAr Data at 200 V/cm

Kr (Global Fit)85

Ar (Global Fit)39

4

Intrinsic background of Underground Argon

39Ar in atmospheric Ar

39Ar in underground Ar

1000 mBq/kg

0.73± 0.11 mBq/kg

With respect to Atmospheric Ar: !> factor of 300 reduction of intrinsic radioactivity in UAr!

~ factor of 1400 reduction of 39Ar activity

Background in ROI = ~50% β-events + ~50% of 𝛾-events Results from the first use of low radioactivity argon in a dark matter search, Phys.Rev. D93, no.8, 08110 (2016)

Multidim.!spectral fit of MC (g4ds) on

AAr/UAr!plus delayed coincidence

tagging

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Dark Matter search data for 70d UAr

Results from the first use of low radioactivity argon in a dark matter search, Phys.Rev. D93, no.8, 08110 (2016)

S1 [PE]50 100 150 200 250 300 350 400 450

90

f

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

0

50

100

150

200

250

50%90% 99%

WIMP Search Region

]nr

Energy [keV20 40 60 80 100 120 140 160 180 200

NR acceptance contours from AmBe in

DS50 + SCENENo events in the

WIMP search region.

Reject:!abnormal clustering of S1 signal!prompt/delayed signal in LSV !preceding 𝜇-like event in vetoes!top and bottom of TPC in drift

AAr!!

UAr

Select !Single scatters!Use Hinkley f90 model!Fit to AAr data Scale to UAr data!Derive 0.01 ER leakage ev. / S1 bin

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Latest DarkSide-50 Dark Matter search result

Results from the first use of low radioactivity argon in a dark matter search, Phys.Rev. D93, no.8, 08110 (2016)!PLOT adapted from Results from a search for dark matter in the complete LUX exposure arXiv:1608.07648 (2016)

101 102 103 104 105

WIMP Mass [GeV/c2]

10�2

10�1

100

101

102

103

WIM

P–nu

cleo

ncr

oss

sect

ion

[zb]

PandaX–II 2016XENON100 2016Dark

Side–50 2015

LUX WS2013

LUX WS2014–16

LUX WS2013+WS2014–16

8B

10�46

10�45

10�44

10�43

10�42

WIM

P–nu

cleo

ncr

oss

sect

ion

[cm

2 ]

0.007 t yr0.01 t yr

LUX WS2

013

DarkSide-50 !

3yr projectio

n

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DarkSide-50 Short Term PlanNew data almost one full year: !-test and utilize blind analysis in steps !-re-optimize full analysis chain!-implement improved background model for ERs !-finalize background model for “Cherenkov plus ER” events

*CALIS - a CALibration Insertion System for the DarkSide-50 dark matter search experiment - Paper submitted!**Effect of Low Electric Fields on Alpha Scintillation Light Yield in Liquid Argon - Paper submitted

Other studies/publications: !-G4DS simulation framework!-G4DS recombination model !-ER background spectrum!-f90 model!-alpha background!-alpha yield**!-combined energy scale!-detector performance!-CALIS*!-S2/S1!-Effective field theory

S1 [PE]38000 40000 42000 44000 46000

10

20

30 0 V/cm

S1 [PE]38000 40000 42000 44000 46000

2

4

6 50 V/cm

S1 [PE]38000 40000 42000 44000 46000

Counts

5

10

15 100 V/cm

S1 [PE]38000 40000 42000 44000 46000

5

10 150 V/cm

S1 [PE]38000 40000 42000 44000 46000

200

400

600

800200 V/cm

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DarkSide-20k challenges and status

15m11m

10m

16m

8m4m

2.9m0.35m

@LNGS @LNGS

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How to collect 50 000 kg of underground argon!

and then purify and distill to arrive to 30 000 kg by 2020 ?

Each purification or distillation step introduces a loss.

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URANIA and ARIA

Aria !Seruci1 - purification of UAr !

Seruci2- isotopic separation of Ar-39 !Rate @150kg/d !

Depletion factor goals:!~10 for Ar-39 and >1000 for N2,02,Kr per

pass

Urania !UAr extraction/

purification@100kg/d !Ar extraction expected to

start in 2017.Extraction&purification!@upgraded Colorado

facility

Des

tilla

tion

via

350m

tall

colu

mn

@ S

eruc

i min

e

Urania in cooperation with Kinder Morgan !ARIA in cooperation with Regione Sardegna (production of other isotopes of interest for medical application)

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How to provide 14 m2 of single-photon sensitive and radiopure

surface with < 10 000 number of readout channels?

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DarkSide-20k Photodetector module

SiPM development by FBK/TIFPA. TIA=Trans-Impedance Amplifier. SNR=Signal to Noise Ratio

Power <250mW

Sapphire substrate

FEB !with Cryo-TIA, transmitter

at Sapphire PCB!SNR>6!

bandwidth>20MHz

50x50mm2 SiPM tile

FR4 PCB substrate

FEB !with Cryo-TIA,

transmitter at FR4 PCB!SNR>6!

bandwidth>20MHz

20x20mm2 SiPM tile

Power <250mWconceptual sketch

KEY GOALS ACHIEVED IN R&D

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FBK NUV-HD-LF-HRq SiPM technology

publication in preparation

2. high dynamic range !via (25-35 𝜇m) cell size

1. peak efficiency in NUV

5V, NUV-HD LF 25 um cell

OV [V]1 2 3 4 5 6 7 8

]2DCR [Hz / mm

-410

-310

-210

-110

3. low intrinsic electric field

Temperature (K)

Over Voltage (V)

Dar

kCur

rent

Rate

[Hz/

mm

2 ]

T [K]50 100 150 200 250 300

AP Probability

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

OV3 V4 V5 V6 V

4. high value of quenching resistor

Afte

rPul

sing

Pro

babi

lity

Temperature (K)

NUV-HD LF 25 um cell

NUV-HD LF 25 um cell LN2

T [K]50 100 150 200 250 300

DiCT Probability

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

OV3 V4 V5 V6 V5. physical trench isolation

Dire

ct C

ross

-Tal

k Pr

ob.

NUV-HD LF 25 um cell

preliminary

preliminary preliminary

preliminary

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Hybrid scheme for SiPMs summing

TIA

SiPMs

TIA

SiPMs

Parallel Configuration Series/Parallel Configuration

+Vb +Vb Optimization of summed capacitance and signal input to!

Cryogenic Trans-Impedance Amplifier!and differential (optical) transmitter.

Transmitter

Maintain SNR>6 for high threshold efficiency at SPE and photon timing ~10ns for Pulse Shape Discrimination

Amplitude [mV]-20 0 20 40 60 80 100 120 140 160 180

Counts / [0.25 mV]

0

200

400

600

800

1000

1200

1400

= 2.8 mV σ Baseline: mean = 0 mV,

= 3.0 mVσ SPE peak: mean = 17 mV,

SNR: 6.0

!SNR = SPE/𝜎baseline: ~6!

~5V OV; LN2 NUV-HD-LF 5mmx5mm

preliminary

4p4s

publication in preparation

20x20mm2

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Cryogenic system

based on DarkSide-50 cryogenic system

bi-directional LAr line

LAr to heat exchanger and purification

GAr to heat exchanger and purification system!

LN2 powered LAr condenser

LAr to recovery

LAr from heat exchanger, radon trap and purification

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Dual-phase octagonal TPC

ITO on bonded acrylic for electrodes !Cu field cage shrinks with reflector !

200V/cm drift field !Teflon as reflector!

TPB as wavelength shifter !stainless steel (titanium) cryostat

Full size components scaled down (1ton) prototype in 2017. Things in bold differ from DarkSide-50

liquid level control via diving bell!5210 SiPMs-based PDM modules !

Cu motherboard holds 25 PDM !extraction linear grid Active mass !

23 tons

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What is the perspective of DarkSide-20k?

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°z/z

0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2

Relative Light Yield

0.9

0.92

0.94

0.96

0.98

1

1.02

1.04

1.06

1.08

1.1

DarkSide-50 Data

G4DS Simulation

Fit

18

DarkSide-20k light yield via G4DS

Light yield for 39Ar with an electric field of 200 V/cm!

~ 9 PE/keV !assuming 40% PDE of PDM

°z/z

0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2

S1 Light Yield [PE / keV]

0

2

4

6

8

10

12

14

16

0

5

10

15

20

25

30

Normalized vertical coordinate.

Center BottomTop

Ligh

t yie

ld P

E/ke

V]

G4DS = Monte Carlo simulation with detailed geometry, electronics chain, tuned and validated optics

parameters for S1 on various DarkSide-50 data.

See P.Agnes talk “g4ds the DarkSide simulation tool” at UCLA DM 2016

Validation

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Modeling ER and NR response in LAr

See P.Agnes talk “g4ds the DarkSide simulation tool” at UCLA DM 2016

G4DS = also models the recombination probability as a function of recoil energy using DarkSide-50 data inputs from endpoint of 39Ar, 83mKr

summed peak and 37Ar.

validations for ER

tuning for ER Mei Model for NR quenching +

AmBe !validations

for NR

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DarkSide-20k Background budget

ROI= 30-200keVr. Events in ROI have no veto, no fiducial, no PSD cut. 222Rn level in DS50 is <2𝜇Bq/kg

Background / [100t yr]

Events in ROI / [100t yr]Background

Internal β/𝛾39Ar = DS-50!

85Kr, 222Rn = << 1.8 x 108 0.06g4ds PSD sim

Internal NRs <<< <<<e -𝜈pp scatters~200ev/ty 2 x 104 <<<

External NRs <154 <0.12g4ds Veto sim

Cosmogenic NRs𝜈-induced NRs 1.6

Cosmogenic β/𝛾 3 x 105 <<0.01<0.1

surface is active

PTFE/SSg4ds Veto sim

g4ds Veto sim

222Rn = DS50 1 x 105“What if?” <<<

“What with?” Cherenkov + β/𝛾 ongoing analysis, it is rare, pattern!and fiducial cuts are effective

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DarkSide-20k PSD simulation

Cold + Warm !Amplifier

Discriminator TDC HITS Count number of PDMs!arrival time resolution ~10ns

X5210

RC shape ADC Charge Pulse integral!keep dynamic rangebaseline

specifications

S1 [PE]50 100 150 200 250 300 350 400 450

200

f

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

1

10

210

310

410

]ee

Energy [keV5 10 15 20 25 30 35 40 45 50

0.001 evts/1 PE leakage

G4DS ERs simulation:!!

S1 light yield = 9PE/keV @200V/cm!

!39Ar as in DS-50!

! f200 = fraction of light in the

first 200ns

high NR acceptance ~90%

100 t yr exposure

~50keVr

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Sensitivity of DarkSide-20k

]2 [GeV/cχ M10 210 310 410

]2 [cm

σ

-5010

-4910

-4810

-4710

-4610

-4510

-4410

-4310

-4210

-4110

DarkSide-50

(2015)

DarkSide-50

(3 yr proj.)

Coherent neutrino-nucleus scattering floor

WARP (2007)

PandaX-II (2

016)XENON1

00 (2012)

LUX (2016)

CDMS(2015)

PICO (2015)

DarkSide-20k

(100 t yr p

roj.)

DarkSide-20k

(200 t yr p

roj.)

Argo (1000 t

yr proj.)-induced N

Rν1

plotted discovery limit for LXe detector

0.007 t yr0.1 t yr

100 t yr

Background-free exposure of 100 t yr !reaching 1.2 x10-47cm2 at DM mass of 1TeV/c2!

( with 39-Ar level as in DS-50)

LZ/XeNT

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DarkSide-20k Plans

Number of collaborating institutions is growing.

Proposal is submitted to NSF and INFN.

Full size components scaled down (1ton) TPC prototype including is planned for 2017. Material Screening Strategy is being finalized.

Continue with photodector modules R&D to optimize performance.!Start setting up facilities for mass production and testing.

PDM testing facility @Naples!Capacity: 4 mother boards

Continue with production of ARIA modules and testing. ! ARIA module testing

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Bq / 100 tonne]µRadon Activity [ 10 20 30 40 50 60 70 80 210 210×2

Uncertainty [%]

0

5

10

15

20

25

30CNO (HZ)

pep (HZ)

Be (HZ)7

CNO (LZ)

pep (LZ)

Be (LZ)7

Energy [MeV]1−10×6 1 2 3 4

yr]

× 400 tonne

×Events / [10 keV

1

10

210

310MC Data

AllνBe-7

νCNO-

νpep-νB-8

P32

Radon

Other Cosmogenics

24

Solar 𝜈 detection in dual-phase LAr TPC

8cpd/100t is approx.100𝜇Bq/100t; Borexino Rn level < 0.57cpd/100t!Solar neutrino detection in a large volume double-phase liquid argon experiment, JCAP 08 (2016

Toy MC study for 300t (100t fiducial) LAr TPC@LNGS.!

400tyr exposure

CNO LZCNO HZ

PEP HZ/LZ

7Be HZ/LZ

Energy [MeV]1−10×6 1 2 3 4

yr]

× 400 tonne

×Events / [10 keV

1

10

210

310MC Data

AllνBe-7

νCNO-

νpep-νB-8

P32

Radon

Other Cosmogenics

Energy [MeV]1−10×6 1 2 3 4

yr]

× 400 tonne

×Events / [10 keV

1

10

210

310MC Data

AllνBe-7

νCNO-

νpep-νB-8

P32

Radon

Other Cosmogenics

directly measure CNO 𝜈s! !

improve precision on !7Be/pep 𝜈s!

!discriminate between two solar metallically models

Unc

erta

inty

[%]

“Conservative” scenario: 222Rn @100𝜇Bq/100t

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25]2 [GeV/cχ M

10 210 310 410

]2 [cm

σ

-5010

-4910

-4810

-4710

-4610

-4510

-4410

-4310

-4210

-4110

DarkSide-50

(2015)

DarkSide-50

(3 yr proj.)

Coherent neutrino-nucleus scattering floor

WARP (2007)

PandaX-II (2

016)XENON1

00 (2012)

LUX (2016)

CDMS(2015)

PICO (2015)

DarkSide-20k

(100 t yr p

roj.)

DarkSide-20k

(200 t yr p

roj.)

Argo (1000 t

yr proj.)-induced N

Rν1

plotted discovery limit for LXe detector

0.007 t yr0.1 t yr

100 t yr

precision measurements on low energy solar 𝜈s!extend dark matter sensitivity for higher masses via bck. subtraction!

*explore 1D Directionality via columnar recombination

LZ/XeNT

1000 t yr

Argo = concept for 300 t LAr TPC

*R&D efforts ongoing; see ReD experiment@Naples and Measurement of scintill.and ionization yield and scintill. pulse shape from NRs in LAr Phys. Rev. D 91, (2015)

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300 t LAr TPC conceived to reach 1000 t yr exposure for precision measurement of solar neutrinos and expanded reach of DM search

Measured 39Ar level in UAr to be factor 1400 smaller than in AAr.Efficiency of the Neutron Veto via delayed capture is >99.1%.More data for new DM search and investigation of rare backgrounds. (Cherenkov events in coincidence with ER event) D

arkS

ide-

50

Critical R&D facilities: URANIA, ARIA and prototype development are already underway.A SiPM based, large-area photo-detection module @ LAr temperature has been demonstrated Feasible to explore DM up to neutrino floor for MDM>100GeV in background-free mode thanks to PSD against 𝜈 induced ERs and intrinsic/dissolved radioactive nuclei inducing ERs.

Dar

kSid

e-20

kAR

GO

collaboration:

Summary

Work supported by NSF, INFN, DOE, NCN and others. LNGS and FNAL lab support.