3rd Berkeley Workshop on the Direct Detection of

DARKSIDE:CHALLENGES, PERSPECTIVES AND PLANS

Emilija Pantic UC DAVIS for the DarkSide collaboration

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

Look for references here 1 [email protected] http://darkside.lngs.infn.it/collaboration 26 DarkSide-50 LAr dual phase TPC 3D positioning O (few mm) Light + Charge S2/S1 discrimination of ERs Pulse shape discrimination of ERs f90 = fraction of S1 in the first 90ns 1

Eextr 90 f 35000 S2 0.9 0.8 Nuclear Recoils 30000 50% 65% - - 0.7 80% e e 90% 25000 - - Edrift e e 0.6 e- e- 200V/cm 20000 f90 0.5

S1 0.4 15000

0.3 Electronic Recoils 10000 0.2 5000 0.1

0 0 1 100 150 200 250 300 350 400 450 46kg of LAr S1S1 [PE] [PE] 38 3” PMTs 7 TPB as wavelength shifter ER Rejection power >10 2016 Pantic (UC Davis) on DarkSide @ Berkeley Workshop cathode/anode = ITO on fused silica 83mKr S1 Light Yield: Teflon as reflector 7.0 ± 0.3 PE/keV @ 200 V/cm extraction grid 2 First Results from the DarkSide-50 Dark Matter Experiment at LNGS, Phys.Lett. B 743 26 DarkSide-50 Veto Detectors: 30t Liquid Scintillator Veto (LSV) = TMB + PPO + PC 1000t Water Cherenkov Veto (WCV) Neutrons that scatter in the TPC can be detected via capture

signal on 10B or thermalization signal in LSV. radiopure Tag radiogenic n Tag radiogenic � Tag cosmogenic n � � n prompt prompt

LSV delayed LSV LSV

Water WCV WCV WCV Pantic (UC Davis) on DarkSide @ Berkeley Workshop 2016 Pantic (UC Davis) on DarkSide @ Berkeley Workshop >99.1% efficiency to veto radiogenic neutrons via delayed capture on 10B and 1H (AmBe + MC) 3 The veto system of the DarkSide-50 experiment, JINST 11, no.03, P03016 (2016) 26 Intrinsic background of Underground With respect to Atmospheric Ar: > factor of 300 reduction of intrinsic radioactivity in UAr ~ factor of 1400 reduction of 39Ar activity −1 10 AAr Data at 200 V/cm

s] (LSV Anti-coinc.) × −2 UAr Data at 200 V/cm Multidim. 10 39Ar in (LSV Anti-coinc.) kg 85

× Kr (Global Fit) spectral fit of 10−3 atmospheric Ar MC (g4ds) on 1000 mBq/kg 39Ar (Global Fit) AAr/UAr 10−4 plus delayed −5 coincidence 10 tagging 39Ar in 10−6 Events / [50 PE underground Ar −7 10 0.73± 0.11 mBq/kg Pantic (UC Davis) on DarkSide @ Berkeley Workshop 2016 Pantic (UC Davis) on DarkSide @ Berkeley Workshop 10−8 0 1000 2000 3000 4000 5000 6000 S1 [PE]

Background in ROI = ~50% β-events + ~50% of �-events 4 Results from the first use of low radioactivity argon in a dark matter search, Phys.Rev. D93, no.8, 08110 (2016) 26 Dark Matter search data for 70d UAr Reject: Select abnormal clustering of S1 signal Single scatters AAr prompt/delayed signal in LSV Use Hinkley f90 model preceding �-like event in vetoes Fit to AAr data Scale to UAr data UAr top and bottom of TPC in drift Derive 0.01 ER leakage ev. / S1 bin Energy [keVnr] 20 40 60 80 100 120 140 160 180 200 1 90 f 0.9 WIMP Search Region 250 0.8 50% 0.7 90% 99% 200 0.6 No events in the NR acceptance contours from AmBe in WIMP search 0.5 150 DS50 + SCENE region. 0.4 100 0.3

0.2 2016 Pantic (UC Davis) on DarkSide @ Berkeley Workshop 50 0.1 0 0 50 100 150 200 250 300 350 400 450 S1 [PE] 5 Results from the first use of low radioactivity argon in a dark matter search, Phys.Rev. D93, no.8, 08110 (2016) 26 Latest DarkSide-50 Dark Matter search result 0.007 t yr 3 42 10 10 0.01 t yr ] 2

DarkSide-50 2 LUX3yr projection WS2013 43 10 DarkSide–50 2015 10

LUX WS2014–16

1 XENON100 2016 44 10 10

8B PandaX–IILUX 2016 WS2013+WS2014–16 LUX WS2013 0 45 10 10

1 46 10 10 WIMP–nucleon cross section [zb] Pantic (UC Davis) on DarkSide @ Berkeley Workshop 2016 Pantic (UC Davis) on DarkSide @ Berkeley Workshop WIMP–nucleon cross section [cm 2 10 101 102 103 104 105 WIMP Mass [GeV/c2] 6 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) 26 DarkSide-50 Short Term Plan New data almost one full year: -test and utilize blind analysis in steps -re-optimize full analysis chain -implement improved background model for 30 0 V/cm ERs 20 10

38000 40000 42000 44000 46000 -finalize background model for “Cherenkov S1 [PE] 6 50 V/cm plus ER” events 4 2

38000 40000 42000 44000 46000 Other studies/publications: ! S1 [PE] 15 100 V/cm -G4DS simulation framework! 10 -G4DS recombination model ! 5 -ER background spectrum! Counts 38000 40000 42000 44000 46000 S1 [PE] -f90 model! 10 150 V/cm

-alpha background! 5 -alpha yield**!

38000 40000 42000 44000 46000 800 S1 [PE] -combined energy scale! 200 V/cm -detector performance! 600 2016 Pantic (UC Davis) on DarkSide @ Berkeley Workshop 400 -CALIS*! 200

-S2/S1! 38000 40000 42000 44000 46000 -Effective field theory S1 [PE] 7 *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 26 DarkSide-20k challenges and status

2.9m 0.35m

16m 8m 4m

10m Pantic (UC Davis) on DarkSide @ Berkeley Workshop 2016 Pantic (UC Davis) on DarkSide @ Berkeley Workshop @LNGS @LNGS 11m 15m 8 26 How to collect 50 000 kg of underground argon and then purify and distill to arrive to 30 000 kg by 2020 ? Pantic (UC Davis) on DarkSide @ Berkeley Workshop 2016 Pantic (UC Davis) on DarkSide @ Berkeley Workshop

9 Each purification or distillation step introduces a loss. 26 URANIA and ARIA Urania UAr extraction/ purification@100kg/d Ar extraction expected to Extraction&purification start in 2017. @upgraded Colorado facility

Aria Seruci1 - purification of UAr Seruci2- isotopic separation of Ar-39 Rate @150kg/d

Depletion factor goals: 2016 Pantic (UC Davis) on DarkSide @ Berkeley Workshop ~10 for Ar-39 and >1000 for N2,02,Kr per pass

Destillation via 350m tall column @ Seruci mine

Urania in cooperation with Kinder Morgan ! 10 ARIA in cooperation with Regione Sardegna (production of other isotopes of interest for medical application) 26 How to provide 14 m2 of single- photon sensitive and radiopure surface with < 10 000 number of readout channels? Pantic (UC Davis) on DarkSide @ Berkeley Workshop 2016 Pantic (UC Davis) on DarkSide @ Berkeley Workshop

11 26 DarkSide-20k Photodetector module

KEY GOALS ACHIEVED IN R&D

50x50mm2 SiPM tile 20x20mm2 SiPM tile

FEB FEB with Cryo-TIA, transmitter with Cryo-TIA, at Sapphire PCB transmitter at FR4 PCB SNR>6 SNR>6 bandwidth>20MHz bandwidth>20MHz

Sapphire substrate FR4 PCB substrate

Power <250mW Power <250mW conceptual sketch Pantic (UC Davis) on DarkSide @ Berkeley Workshop 2016 Pantic (UC Davis) on DarkSide @ Berkeley Workshop

12 SiPM development by FBK/TIFPA. TIA=Trans-Impedance Amplifier. SNR=Signal to Noise Ratio 26 FBK NUV-HD-LF-HRq SiPM technology 1. peak efficiency in NUV 2. high dynamic range via (25-35 �m) cell size

10-1

] preliminary 2 3. low intrinsic electric field

] preliminary -2 2 10

5V, NUV-HD LF 25 um cell

-3

DCR [Hz / mm 10 Temperature (K)

0.4 DarkCurrentRate [Hz/mm NUV-HD LF 25 um cell LN2 10-4 OV 0.41 2 3 4 5 6 7 8 0.35 3 V 4. high value of quenching resistor OV [V] 4 V OV 0.35 Over Voltage (V) 3 V 0.3 5 V 6 V 4 V 0.3 5 V 0.25 5. physical trench isolation6 V 0.25 preliminary 0.2 preliminary 0.2 0.15 0.15 AP Probability Pantic (UC Davis) on DarkSide @ Berkeley Workshop 2016 Pantic (UC Davis) on DarkSide @ Berkeley Workshop

0.1 DiCT Probability 0.1 0.05 NUV-HD LF 25 um cell 0.05 NUV-HD LF 25 um cell AfterPulsing Probability 0 50 100 150 200 250 300 0 Direct Cross-Talk Prob. Direct Cross-Talk 50 100 150 200 250 300 TemperatureT [K] (K) T [K] 13 publication in preparation 26 Hybrid scheme for SiPMs summing SiPMs Maintain SNR>6 for high threshold efficiency at SPE and photon timing ~10ns for Pulse Shape Discrimination SiPMs

+V +Vb b Optimization of summed capacitance TIA TIA Transmitter and signal input to Cryogenic Trans-Impedance Amplifier and differential (optical) transmitter.

1400

1200 2 4p4s Baseline:20x20mm mean = 0 mV, σ = 2.8 mV Parallel Configuration Series/Parallel Configuration SPE peak: mean = 17 mV, σ = 3.0 mV 1000 SNR SNR: 6.0 = SPE/�baseline: ~6

800 600 preliminary 400 Counts / [0.25 mV] Pantic (UC Davis) on DarkSide @ Berkeley Workshop 2016 Pantic (UC Davis) on DarkSide @ Berkeley Workshop 200 ~5V OV; LN2 NUV-HD-LF 5mmx5mm

0 -20 0 20 40 60 80 100 120 140 160 180 Amplitude [mV] 14 publication in preparation 26 Cryogenic system LAr from heat exchanger, radon trap and purification LN2 powered LAr condenser LAr to heat GAr to heat exchanger exchanger and and purification purification system Pantic (UC Davis) on DarkSide @ Berkeley Workshop 2016 Pantic (UC Davis) on DarkSide @ Berkeley Workshop LAr to recovery bi-directional LAr line 15 based on DarkSide-50 cryogenic system 26 Dual-phase octagonal TPC

liquid level control via diving bell 5210 SiPMs-based PDM modules Cu motherboard holds 25 PDM Active mass extraction linear grid 23 tons

ITO on bonded acrylic for electrodes Cu field cage shrinks with reflector 200V/cm drift field Pantic (UC Davis) on DarkSide @ Berkeley Workshop 2016 Pantic (UC Davis) on DarkSide @ Berkeley Workshop Teflon as reflector TPB as wavelength shifter stainless steel (titanium) cryostat 16 Full size components scaled down (1ton) prototype in 2017. Things in bold differ from DarkSide-50 26 What is the perspective of DarkSide-20k? Pantic (UC Davis) on DarkSide @ Berkeley Workshop 2016 Pantic (UC Davis) on DarkSide @ Berkeley Workshop

17 26 DarkSide-20k light yield via G4DS

1.1

1.08 Validation G4DS = Monte Carlo simulation DarkSide-50 Data 1.06 G4DS Simulation with detailed geometry, electronics 1.04 Fit chain, tuned and validated optics 1.02 1 parameters for S1 on various 0.98 0.96

DarkSide-50 data. Relative Light Yield 0.94

0.92

0.9 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 z/z °

16 30

14 39 25 Light yield for Ar with an 12 20 electric field of 200 V/cm 10 ~ 9 PE/keV 8 15 6 10 assuming 40% PDE of PDM Light yield PE/keV] 4

S1 Light Yield [PE / keV] 5 2 Top Center Bottom 2016 Pantic (UC Davis) on DarkSide @ Berkeley Workshop 0 0 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 z/z ° Normalized vertical coordinate.

18 See P.Agnes talk “g4ds the DarkSide simulation tool” at UCLA DM 2016 26 Modeling ER and NR response in LAr 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.

Mei Model for tuning for ER + NR quenching

validations for ER AmBe

validations 2016 Pantic (UC Davis) on DarkSide @ Berkeley Workshop for NR

19 See P.Agnes talk “g4ds the DarkSide simulation tool” at UCLA DM 2016 26 DarkSide-20k Background budget Events in ROI / Background / Background [100t yr] [100t yr] 39Ar = DS-50 Internal β/� 8 g4ds PSD sim 0.06 85Kr, 222Rn = << 1.8 x 10 surface is active Internal NRs <<< <<<

~200ev/ty e -�pp scatters 2 x 104 <<< PTFE/SS External NRs <154 g4ds Veto sim <0.12 Cosmogenic β/� 3 x 105 g4ds Veto sim <<0.01 Cosmogenic NRs g4ds Veto sim <0.1 �-induced NRs 1.6

“What if?” 222Rn = DS50 1 x 105 <<< 2016 Pantic (UC Davis) on DarkSide @ Berkeley Workshop ongoing analysis, it is rare, pattern “What with?” Cherenkov + β/� and fiducial cuts are effective 20 ROI= 30-200keVr. Events in ROI have no veto, no fiducial, no PSD cut. 222Rn level in DS50 is <2�Bq/kg 26 DarkSide-20k PSD simulation

X5210 Discriminator TDC HITS Count number of PDMs! arrival time resolution ~10ns Cold + Warm ! Amplifier Pulse integral! RC shape ADC Charge baseline keep dynamic range specifications

Energy [keV ] ee 5 10 15 20 25 30 35 40 45 50 G4DS ERs simulation: 1 104 0.9 high NR acceptance ~90% 0.8 0.001 evts/1 PE leakage S1 light yield = 9PE/keV 103 0.7 @200V/cm 0.6

200 0.5 2 f 10 39 0.4 Ar as in DS-50 0.3 10 0.2 2016 Pantic (UC Davis) on DarkSide @ Berkeley Workshop f200 = fraction of light in the 0.1 100 t yr exposure 0 1 50 100 150 200 250 300 350 400 450 first 200ns S1 [PE] ~50keVr 21 26 Sensitivity of DarkSide-20k 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) 10-41

WARP (2007) 10-42 PICO (2015) 0.007 t yr 10-43 DarkSide-50 (2015) 0.1 t yr

-44 CDMS 10 (2015) DarkSide-50 (3 yr proj.) XENON100 (2012) ] 2 -45 LUX (2016) 10 PandaX-II (2016) LZ/XeNT

[cm -46

σ 10 100 t yr

DarkSide-20k (100 t yr proj.) -47 10 1 ν-induced NR DarkSide-20k (200 t yr proj.) Argo (1000 t yr proj.) 10-48 Pantic (UC Davis) on DarkSide @ Berkeley Workshop 2016 Pantic (UC Davis) on DarkSide @ Berkeley Workshop 10-49 Coherent neutrino-nucleus scattering floor plotted discovery limit for LXe detector 10-50 10 102 103 104 M [GeV/c2] χ 22 26 PDM testing facility DarkSide-20k Plans @Naples Capacity: 4 mother Proposal is submitted to NSF and INFN. boards Continue with photodector modules R&D to optimize performance. Start setting up facilities for mass production and testing. Continue with production of ARIA modules and testing. ARIA module testing Full size components scaled down (1ton) TPC prototype including is planned for 2017. Material Screening Strategy is being finalized. 2016 Pantic (UC Davis) on DarkSide @ Berkeley Workshop

23 Number of collaborating institutions is growing. 26 MC Data 3

yr] 10 All × 7Be-ν Solar � detectionCNO-ν in dual-phase LAr TPC MC Data pep-ν 3 8 Toy MC study for 300t (100t

yr] 10 B- MC Data ν 3 All

yr] 10 × All32

× 7 fiducial) LAr TPC@LNGS. 2 7 P 10 Be-ν Be-ν CNO-ν CNO- pep-Radonν ν 8 400tyr exposure B-ν 102 pep- 32POther Cosmogenics 400 tonne ν Radon 8 Other Cosmogenics × 400 tonne

× B-ν 2 32P 10 10 Radon “Conservative” scenario: 10 222 Other Cosmogenics Rn @100�Bq/100t 400 tonne 1 × Events / [10 keV

6×10−1 1 2 3 4 30 Energy [MeV] CNO (HZ) 10 pep (HZ) 1 25 7Be (HZ) directly measure CNO �s CNO (LZ) pep (LZ) HZ 20 7Be (LZ) CNO

Events / [10 keV

Uncertainty [%] LZ improve precision on 15 CNO HZ/LZ 1 6×10−1 1 7Be/pep �s2 3 4 PEP Energy10 [MeV]

Uncertainty [%]

2016 Pantic (UC Davis) on DarkSide @ Berkeley Workshop Events / [10 keV 5 discriminate between two 7Be HZ/LZ −1 0 6×10 1 solar metallically2 models3 4 10 20 30 40 50 60 70 80 102 2×102 Energy [MeV] Radon Activity [ µBq / 100 tonne]

8cpd/100t is approx.100�Bq/100t; Borexino Rn level < 0.57cpd/100t! 24 Solar neutrino detection in a large volume double-phase liquid argon experiment, JCAP 08 (2016 26 Argo = concept for 300 t LAr TPC precision measurements on low energy solar �s extend dark matter sensitivity for higher masses via bck. subtraction *explore 1D Directionality via columnar recombination 10-41

WARP (2007) 10-42 PICO (2015) 0.007 t yr 10-43 DarkSide-50 (2015) 0.1 t yr

-44 CDMS 10 (2015) DarkSide-50 (3 yr proj.) XENON100 (2012) ] 2 -45 LUX (2016) 10 PandaX-II (2016) LZ/XeNT

[cm -46

σ 10 100 t yr

DarkSide-20k (100 t yr proj.) -47 1000 t yr 10 1 ν-induced NR DarkSide-20k (200 t yr proj.) Argo (1000 t yr proj.) 10-48 Pantic (UC Davis) on DarkSide @ Berkeley Workshop 2016 Pantic (UC Davis) on DarkSide @ Berkeley Workshop 10-49 Coherent neutrino-nucleus scattering floor plotted discovery limit for LXe detector 10-50 2 3 4 10 10 2 10 10 Mχ [GeV/c ] *R&D efforts ongoing; see ReD experiment@Naples and Measurement of scintill.and ionization yield and scintill. 25 pulse shape from NRs in LAr Phys. Rev. D 91, (2015) 26 Summary collaboration:

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) DarkSide-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 � induced ERs and DarkSide-20k intrinsic/dissolved radioactive nuclei inducing ERs. Pantic (UC Davis) on DarkSide @ Berkeley Workshop 2016 Pantic (UC Davis) on DarkSide @ Berkeley Workshop 300 t LAr TPC conceived to reach 1000 t yr exposure for precision

measurement of solar neutrinos and expanded reach of DM search ARGO

26 Work supported by NSF, INFN, DOE, NCN and others. LNGS and FNAL lab support. 26