Recent results from the EDELWEISS-III search

52nd Moriond Conference, 19.03.2017 – 24.03.2017 Very High Energy Phenomena in the Universe

Bernhard Siebenborn

KIT – The Research University in the Helmholtz Association www.kit.edu Direct search for Dark Matter

Ge, CF3I, C3F9 Ge, Si 10% energy Ionization

liquid Xe/Ar Target Heat Al2O3, LiF 100% energy slowest cryogenics

Light 1% energy CaWO4, BGO fastest NaI, liqu.Xe no surface effects

2 Bernhard Siebenborn Direct search for Dark Matter DAMIC CoGeNT, CDMSlite CDEX, Ge, CF3I, C3F9 Ge, Si EDELWEISS, PICO 10% energy SuperCDMS Ionization

DarkSide, DEAP-3600 liquid Xe/Ar Target Heat Al2O3, LiF 100% energy LUX, PandaX-II, slowest CRESST-1 cryogenics XENON100, XENON1T Light 1% energy CaWO4, BGO fastest no surface effects NaI, liqu.Xe CRESST DAMA/LIBRA, DM-Ice, ANAIS, KIMS, SABRE

3 Bernhard Siebenborn Liquid noble gas vs. cryogenic bolometers

EDELWEISS

DAMIC

DAMA/LIBRA CDMSLite2 Cryogenic detectors CRESST(2015) low thresh, high CRESST(2012) energy resolution CDMS-LT

n floor

x 10.000 Liquid noble gas: target mass, low bgd Billard, Strigari, Figueroa-Feliciano PRD 89 (2014)

4 Bernhard Siebenborn EDELWEISS collaboration

CEA Irfu/Iramis (Saclay) CSNSM (Orsay) Institut Néel (Grenoble) IPNL (Lyon) LPN (Marcoussis)

KIT (Karlsruhe)

JINR (Dubna)

University of Oxford

EDELWEISS 2016 @ KIT University of Sheffield

1

-

y y

1 1

-

sr

2 2 -

Muon intensity, m intensity, Muon 5 m/m2/day 4800 mwe Depth, meters water equivalent (deepest in Europe)

5 Bernhard Siebenborn EDELWEISS-III FID800 detectors

 e- WIMP

푈  Q → E WIMP Ion + NTD h

ΔT ~ Eheat = Erecoil + ENTL

Top = 18mK Ø=70mm, h=40mm 2 GeNTDs heat sensors additional heat by drifting charges (Neganov-Trofimov-Luke effect): Electrodes: concentric Al rings

XeF surface treatment: to ensure low leakage 퐸푁푇퐿 = 푁 ∙ 푒 ∙ 푈 2 current (<1 fA) between adjacent electrodes

JLTP(2014)176:182

6 Bernhard Siebenborn EDELWEISS FID800 detectors

Fully InterDigitized ~870g HPGe detectors Challenges: Low event rate: <1 evt/kg/year Ctop=+4V Vtop=-1.5V Small energy deposit: O(keV) NTD Background events by: b, g, n

m - induced background 309 –

e- B 681 (2009) 305 (2009) B681

FID800 Lett

h+ Phys

NTD

Cbott=-4V Vbott=+1.5V Bulk/Fiducial event: Surface event:

Signal on Ctop&Cbott Signal on Cbott&Vbott

7 Bernhard Siebenborn EDELWEISS experimental setup

e+,e-, g, Pb shield

m, Muon Veto Cryostat n, Polyethylene shield

8 Bernhard Siebenborn EDELWEISS DAQ system

FPGA based DAQ system Hardware and software trigger, event based read out Integration of external detectors: Muon-Veto Option to change individual bias voltage 0V±70V

Continuous digitization (100kHz, 16bit), optional: 40MHz, 16bit opticalfiber

detectors analog analog/digital DAQ crate, FPGA ethernet DAQ PCs, software at 18mK amplification at conversion trigger, central clock trigger and event 100K with FET storage detector bias, up to based on Auger and

140V KATRIN crate continuous control

inner shielding cryostat

9 Bernhard Siebenborn

Nuclear recoil calibration - event discrimination

AmBe neutron calibration  Clear event-by-event separation electron recoils down to 5 keV energy (nuclear recoils)

 Response to nuclear recoils calibrated

Ionization yield Ionization down to the analysis threshold for low-

mass WIMP searches (1 keVee heat = 2.5 keV nuclear rec.)

nuclear recoils

Recoil Energy (keV)

10 Bernhard Siebenborn Event rejection of γ and surface events

 g rejection factor: < 5.6 x 10-6 JLTP(2012)167:1056 Updated now to < 2.5 x 10-6 with additional detectors + statistics  Surface event rejection (210Pb+210Bi b, 210Po a, 206Pb recoils): < 4 x 10-5 JLTP(2014)176:870 EDELWEISS FID 133Ba calibration (937977 g)

210Pb b 210Po a 206Pb

5 >5000 kg.day 10 kg.day equivalent equivalent

11 Bernhard Siebenborn EDELWEISS-III 2014-2015 science run

161 days of physics data with 24 FIDs: >3000 kgd total exposure

 Low ER bkg: 19 FIDs used in first measurement of cosmogenic production of 3H in Ge

arXiv:1607.04560

<0.1dru

 8 lowest threshold FIDs used for low-mass

WIMP search

12 Bernhard Siebenborn Low mass WIMP search with likelihood analysis

EPJC(2016)76:548 8 lowest threshold detectors

13 Bernhard Siebenborn Results of the likelihood analysis

EPJC(2016)76:548 FID824 Ionisation

2 m=4GeV/c excluded at 90%CL FID824 Heat

14 Bernhard Siebenborn First results of EDELWEISS-III phase

EDELWEISS III BDT JCAP05 (2016) 019  Improvement by x20 to x150 between 7 and 10 GeV wrt EDELWEISS II EDELWEISS-II DAMA/LIBRA

CoGeNT-2012  Limited by heat-only bkd: CDMSLite2 CoGeNT-2013 identification and rejection using the σ = 230 eV resolution on ionization  Ionization resolution is key for rejection  Heat resolution is key for low thresholds

EPJC(2016)76:548

15 Bernhard Siebenborn EDELWEISS 2018 goals: 4x100

Challenges: 1. “Heat only” events  x100 reduction 2018 goal, 350 kg·d 2. HEMT transistor read out

 σion = 200eV  100eV 100 V, actual bgd 3. NTL effect read out

 Vbias = 8V  100V 35000 kg·d 4. Improved heat sensors

 σheat = 500eV  100eV

JLTP(2015)00376R1

16 Bernhard Siebenborn Challenge 1: Detector R&D: reducing heat only events

 Dominant (&reproducible) background at low energy

 Noise, cryogenics, stress from detector suspension: excluded as sources of this background Deported NTD  Remaining suspect: stress from gluing, avoided via:

 Two “deported NTD”, glued on separate sapphire wafer  Photo-lithographed high-Ω NbSi TES, sensitive to athermal phonons

NbSi TES

17 Bernhard Siebenborn Challenge 2: Detector R&D: HEMT read out

JFET  HEMT Reduced intrinsic noise Lower heat load Operates at 4K stage shorter cabling Reduced capacitance Better SNR JLTP(2016)184:505

Successful HEMT amplifier 241Am calibration Baseline with sub-100 eV resolution RMS 91 eVRMS ionization resolution

A. Phipps et al., arXiv:1611.09712 collaboration between SuperCDMS and EDELWEISS

A. Phipps et al., arXiv: 1611.09712

18 Bernhard Siebenborn Challenge 3: Lower threshold by increased bias voltage Neganov-Trofimov-Luke effect Detector bias upgrade: 푉 = 8V  140V ΔT ~ Eheat = Erecoil + ENTL 푏푖푎푠

ENTL= 푁 ∙ 푒 ∙ 푉푏푖푎푠

Prompt phonons 133Ba calibration V Charge propagation bias NTL amplified 356keV γ-line phonons

Pair creation in Ge: 1 keV  340 e-h+ pairs Sensitivity goal: <100 eV

Ionization signal measured in heat channel  No particle discrimination at threshold

19 Bernhard Siebenborn Challenge 3: Lower threshold by increased bias voltage Neganov-Trofimov-Luke effect Detector bias upgrade: 푉 = 8V  140V ΔT ~ Eheat = Erecoil + ENTL 푏푖푎푠

ENTL= 푁 ∙ 푒 ∙ 푉푏푖푎푠

Prompt phonons 133Ba calibration V Charge propagation bias NTL amplified 356keV γ-line phonons

Pair creation in Ge: 1 keV  340 e-h+ pairs Sensitivity goal: <100 eV

Ionization signal measured in heat channel  No particle discrimination at threshold  Ionization as diagnostic signal at higher energy

20 Bernhard Siebenborn Surface event discrimination by rise time

C1 40MS/s

V2 C1 – C2 ADU

C2

fiducial A. Broniatowski et al. PLB681(2009)305 surface

Rise time as complementary Rise time cut at 450ns surface rejection:

95% „surface“ rejection 4.4% efficiency loss „fiducial“

EDW-III 40MHz digitizer (yet restricted to Eion>100keV)

21 Bernhard Siebenborn Detector R&D and MC studies of charge migration

N. Foerster et al., JLTP(2016)184:845

VB = -VD = 2V

VA = VC = 0V

VB = -VD = 50V

VA = VC = 0V

241Am(g, 60keV) Pb, d=1mm VB = -VD = 2V

VA = VC = 0V

VB = -VD = 50V

VA = VC = 0V

MC

N. Foerster, PhD thesis 2017

22 Bernhard Siebenborn Challenge 4: Detector R&D: Thermal model & heat sensor

J. Billard et al., JLTP(2016)184:299  Better understanding of heat signal  Thermal modeling of signal, verified with dedicated R&D  Identification of sensitivity to ballistic phonons  Identification of parasitic heat capacity

Averaged 1 keV template Best fit 95% C.L. band

 Sensitivity of 200 nV/keV  (x6 wrt present FIDs) achieved on 250 g test detectors

23 Bernhard Siebenborn EDELWEISS 2018 goal

EDW-III 350 kg.d, EDW-III background assumed

EPJC (2016) 76:548

100V, s=100eV(heat)

8V, s=100eV(ion)

JLTP(2016)184:308

24 Bernhard Siebenborn Conclusion and Outlook

EDELWEISS-III results 2016

100V EDW-III goals 2018

350kg-days

going beyond (35kg x 1000days) 8V no neutron-bgd, 0.1 x Compton

25 Bernhard Siebenborn Conclusion and Outlook

Going beyond: EDELWEISS-III SuperCDMS + results 2016 EDELWEISS at SNOLab

CRESST-3 phase 1

EDW-III goals 2018

CRESST-3 phase 2

35 ton-days

SuperCDMS@SNOLAB

26 Bernhard Siebenborn