The EDELWEISS Dark Matter Search Astroparticle Physics in Germany, Mainz 17-19.09.2018 Bernhard Siebenborn on behalf of the EDELWEISS collaboration www.kit.edu KIT – The Research University in the Helmholtz Association
WIMPs as Dark Matter Y. Sofue, PASJ, 70-2(2018) Rotation curves of galaxies DM halo Assume DM particle candidate: WIMP gravitation additional “weak” interactions WIMP-nucleus scattering in detector Kinematics keV-scale recoils Potential for WIMP discovery in a detector via combination of ionization heat heat scintillation Ionization scintillation χ Unknown parameters: WIMP cross section Ge WIMP mass credit to Illustris Collaboration 2 Bernhard Siebenborn - EDELWEISS dark matter search Institut für Kernphysik
(low mass) WIMP searches CRESST n -cleus WIMP-nucleon SI cross section (cm 2 ) CDMSLite DAMIC EDELWEISS-III PANDA-X LUX n floor XENON-1t 0.1 1 10 WIMP Mass (GeV/c 2 ) 3 Bernhard Siebenborn - EDELWEISS dark matter search Institut für Kernphysik
(low mass) WIMP searches CRESST n -cleus WIMP-nucleon SI cross section (cm 2 ) threshold CDMSLite DAMIC EDELWEISS-III threshold & exposure & discrimination PANDA-X LUX n floor XENON-1t 0.1 1 10 exposure & WIMP Mass (GeV/c 2 ) discrimination 4 Bernhard Siebenborn - EDELWEISS dark matter search Institut für Kernphysik
EDELWEISS low mass WIMP searches EDELWEISS-III Exploitation of results with 20 kg array EPJC 76 (2016) 548 WIMP-nucleon SI cross section (cm 2 ) EDELWEISS-Surf Ionization channel R&D Improving discrimination to explore the 8 B region with resolution (DMB8) Exploring non-WIMP DM with smaller array Heat channel R&D DMB8 Improving the heat channel resolution to reach lower WIMP masses Above-ground R&D (Surf) and deployment at LSM (LT) 0.1 1 10 WIMP Mass (GeV/c 2 ) 5 Bernhard Siebenborn - EDELWEISS dark matter search Institut für Kernphysik
EDELWEISS collaboration CEA Irfu/Iramis (Saclay) France CSNSM (Orsay) Institut Néel (Grenoble) IPNL (Lyon) LPN (Marcoussis) Germany KIT (Karlsruhe) Russia JINR (Dubna) GB University of Oxford University of Sheffield EDELWEISS 2016 @ KIT 6 Bernhard Siebenborn - EDELWEISS dark matter search Institut für Kernphysik
EDELWEISS-III setup Laboratory: LSM, ~4800m.w.e. rock overburden (deepest in Europe) 5 µ/m 2 /d Active muon veto + PE + Pb shield Clean room, de-radonised air 10-20 mBq/m 3 Cryostat hosting up to 40kg of detectors at 18mK Selection of radio pure material Performance of the EDELWEISS-III experiment for direct dark matter searches JINST 12 (2017) P08010 7 Bernhard Siebenborn - EDELWEISS dark matter search Institut für Kernphysik
EDELWEISS-III detectors ~870g mono-crystal high purity Ge detectors surface event rejection ~10 -5 2 heat sensors per detector (GeNTDs) T op = 18 mK PLB 681 (2009) 305 – 309 Electrodes: Al rings covering all faces C top =+4V V top =-1.5V NTD Calibration: e - 133 Ba g AmBe neutron FID800 h + NTD Clear event-by-event separation down C bott =-4V V bott =+1.5V to ~ keV energy (nuclear recoils) Bulk/Fiducial event: Surface event: Signal on C top &C bott Signal on C bott &V bott 8 Bernhard Siebenborn - EDELWEISS dark matter search Institut für Kernphysik
10 counts/keV/kg/day Axion-like particle searches (e - recoils) 1 Starting point: study of electron recoil spectrum of cosm. activ. Astropart. Phys. 91 (2017) 51 Threshold: 0.8 keV ee to 2 keV ee Analysis extended to higher energy for line search up to 500 keV ee 10 -1 Intensities of observed peaks consistent with known Th/U lines Baseline resolution: 193 eV ee 10 -2 energy (keV) residual/continuum Counts energy (keV) 9 Bernhard Siebenborn - EDELWEISS dark matter search Institut für Kernphysik
ALP and dark photon results (e - recoils) Emission of Axion/ALPs from the sun keV-scale Bosonic DM Kinetic coupling k of dark photon CBRD signal C ompton- 10 -10 10 -10 B remsstrahlung- R ecombination- Solar neutrinos EDELWEISS-II D e-excitation-like signal EDELWEISS-III 10 -11 Kinetic mixing k 10 -12 XENON100 PandaX-II g ae LUX EDELWEISS-III 10 -12 Best Ge-based limits <6 keV 10 -14 Red giants (thanks to surface rejection) 10 -13 Start to explore <1 keV 10 -16 10 -5 10 -4 10 -3 10 -2 10 -1 1 1 10 100 m a (keV/c 2 ) m V (keV/c 2 ) expected sensitivity with improved ionization channel arXiv:1808.02340 10 Bernhard Siebenborn - EDELWEISS dark matter search Institut für Kernphysik
prospects for GeV-range masses Complete study based on present measured backgrounds and resolutions vs possible improvements: PRD 97 (2018) 022003 WIMP-nucleon SI cross section (cm 2 ) 1. Use of Neganov-Luke boost to lower thresholds (increased detector voltage 8 V 100 V ) Projection for 4x800g 2. Improve heat resolution, objective of 800g detectors: 100 eV – 100V 150 days / current bgd s phonon = 500 eV 100 eV (50 eV resolution already achieved on 200 g detector) 0.1 1 10 WIMP Mass (GeV/c 2 ) 11 Bernhard Siebenborn - EDELWEISS dark matter search Institut für Kernphysik
EDELWEISS-LT: NL-boost & improved heat 𝐹𝑗𝑝𝑜 E NL = ∙ 𝑊 𝑐𝑗𝑏𝑡 𝜁 Prompt phonons Charge propagation V bias NL amplified phonons ✔ 100V bias already achieved J. Billard et al., ✔ Observe nucl. recoils down to ~0.1 keV ee JLTP(2016)184:299 ✔ Full ion.+heat readout possible at any V same detector & same AmBe source ionization energy (keV ee ) NTD-B event 133 Ba 356 keV line 8 V 90 V FWHM heat (keV ee ) 1 g 0.1 n 0 4000 8000 12000 0 5 10 15 0 1 2 3 heat energy (keV ee ) Luke boost = 1 + V/3 Total phonon energy (keV) 12 Bernhard Siebenborn - EDELWEISS dark matter search Institut für Kernphysik
resolution improvements on a 32g HPGe R&D with 32g HPGe combined with the objective of testing the above-ground sensitivity to sub-GeV WIMPs optimized NTD heat sensor on a 32g crystal, no electrodes (i.e. 1keV = 1keV NR ) kept at 17 mK in IPNL low-vibration dilution fridge [arXiv:1803.03463] one day blinded for WIMP search in [0-2] keV region 60eV analysis threshold s =18 eV baseline 13 Bernhard Siebenborn - EDELWEISS dark matter search Institut für Kernphysik
unblinding the data No surprise: blinded day = carbon copy of preceding + following days analysis region 8000 dru 0.6-2.0 keV 4000 dru > 7 keV Find maximal WIMP rate compatible with total number of counts observed in the pre-defined windows 90% CL on WIMP signals as function of WIMP mass 14 Bernhard Siebenborn - EDELWEISS dark matter search Institut für Kernphysik
EDELWEISS surface limit WIMP-nucleon SI cross section (cm 2 ) CRESST n -cleus (above ground) Best above-ground limit down to 600 MeV/c 2 : SIMP First sub-GeV limit with Ge, down to 500 MeV/c 2 EDELWEISS-Surf (above ground) Achieved resolution on a smaller detector exceeds by x5 the original LT goal with 800 g detectors EDELWEISS-III Small detectors with lower thresholds to be combined with expertise acquired on HV: threshold reduction by factor (1+V bias /3) in keV ee 0.1 1 10 WIMP Mass (GeV/c 2 ) 15 Bernhard Siebenborn - EDELWEISS dark matter search Institut für Kernphysik
Conclusions & outlook EDELWEISS-III : large detectors with excellent rejection Exploitation of FID to get best ALP limits, enter the sub-keV range EDELWEISS-MELODI: develop large detectors with EDELWEISS design Exploring non-WIMP DM with prototype: ALPs in the 0.1-1 keV range Building block for larger search experiment (DMB8), addressing specifically region where DM signal has to be spectrally separated from solar 8 B neutrinos Prospects in the sub-GeV-WIMP range: beyond EDELWEISS-LT Going beyond original [PRD] goal: 100 eV 18 eV (~500 eV EDW-III) Best surface limit for WIMPs above 0.6 GeV/c 2 Combining excellent energy resolution with NL-boost 2019/2020: intensive R&D in surface labs KIT + U Heidelberg: NL-boosted Ge detectors with MMC phonon sensors DELight 16 Bernhard Siebenborn - EDELWEISS dark matter search Institut für Kernphysik
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