Direct Dark Matter Search with the CRESST-III Experiment

Transcription

1 Direct Dark Matter Search with the CRESST-III Experiment Andrea Mu nster TUM TeVPA 2017

2 CRESST Collaboration A.Mu nster (TUM) Direct Dark Matter Search with CRESST-III 08/08/17 2 / 18

3 Direct Dark Matter Search with CRESST elastic DM particle-nucleus scattering A.Münster (TUM) Direct Dark Matter Search with CRESST-III 08/08/17 3 / 18

4 Working Principle of CRESST Cryogenic Rare Event Search with Superconducting Thermometers located at the Laboratori Nazionali del Gran Sasso (LNGS) target material: CaWO 4 single crystals CaWO 4 crystal A.Münster (TUM) Direct Dark Matter Search with CRESST-III 08/08/17 4 / 18

5 Working Principle of CRESST Cryogenic Rare Event Search with Superconducting Thermometers located at the Laboratori Nazionali del Gran Sasso (LNGS) target material: CaWO 4 single crystals particle interaction heat (phonon) signal read-out with thermometer light signal read-out with light absorber + thermometer heat bath heat bath thermal coupling thermometer light absorber CaWO 4 crystal thermometer thermal coupling A.Münster (TUM) Direct Dark Matter Search with CRESST-III 08/08/17 4 / 18

6 Working Principle of CRESST Cryogenic Rare Event Search with Superconducting Thermometers located at the Laboratori Nazionali del Gran Sasso (LNGS) target material: CaWO 4 single crystals particle interaction heat (phonon) signal read-out with thermometer light signal read-out with light absorber + thermometer reflective and scintillating housing maximize light collection veto surface events heat bath 2 heat bath thermal coupling thermometer light absorber CaWO 4 crystal reflective and scintillating housing thermometer thermal coupling A.Münster (TUM) Direct Dark Matter Search with CRESST-III 08/08/17 4 / 18

7 Background Discrimination energy deposition > 90 % < 10 % phonon signal: precise energy measurement light signal: dependent on type of interacting particle A.Münster (TUM) Direct Dark Matter Search with CRESST-III 08/08/17 5 / 18

8 Background Discrimination energy deposition > 90 % < 10 % phonon signal: precise energy measurement light signal: dependent on type of interacting particle active background discrimination on event-by-event basis: Light Yield = E L E Ph e /γ ROI α O W E Ph [kev] A.Münster (TUM) Direct Dark Matter Search with CRESST-III 08/08/17 5 / 18

9 Results of CRESST-II Phase 2 ( ) CRESST-II 2015: 1 detector crystal mass 300 g exposure 52 kg days threshold 300 ev EUR PHYS J C Volume 76, Number 1 (2016) A.Münster (TUM) Direct Dark Matter Search with CRESST-III 08/08/17 6 / 18

10 Goal for CRESST-III Goal: increase performance via decreasing phonon detector threshold to 100 ev EUR PHYS J C Volume 76, Number 1 (2016) A.Münster (TUM) Direct Dark Matter Search with CRESST-III 08/08/17 7 / 18

11 CRESST-III Phase 1: Detector Modules crystal mass and dimensions: 24 g, (20 x 20 x 10) mm3 holding with CaWO4 sticks fully scintillating housing instrumented sticks (isticks) for holding main crystal veto for events happening in sticks clamp istick Q Q XXXQQ X reflective and scintillating foil CaWO4 crystal with TES light absorber with TES CaWO4 stick (not instrumented) A.Mu nster (TUM) Direct Dark Matter Search with CRESST-III 08/08/17 8 / 18

12 CRESST-III Phase 1: Installed Detectors 10 small detector modules installed majority of CaWO4 crystals produced at Technical University of Munich (TUM) Data taking started in summer 2016 A.Mu nster (TUM) Direct Dark Matter Search with CRESST-III 08/08/17 9 / 18

13 analysis threshold for a high-threshold analysis : 100 ev A.Münster (TUM) Direct Dark Matter Search with CRESST-III 08/08/17 10 / 18 CRESST-III Phase 1: Thresholds preliminary Detector module A hardware threshold 48 ev data taking period 31/10/16-05/07/17 non-blind data set (dynamically growing) 20 % total measuring time (blind) 2540 h total exposure after cuts 2.21 kg days

14 CRESST-III Phase 1: Thresholds preliminary detector module A data taking period 31/10/16-05/07/17 non-blind data set (dynamically growing) 20 % total measuring time (blind) 2540 h total exposure after cuts 2.21 kg days analysis threshold for a high-threshold analysis : 100 ev A.Münster (TUM) Direct Dark Matter Search with CRESST-III 08/08/17 10 / 18

15 CRESST-III Phase 1: Detector Module A exposure: 2.2 kg days e /γ O W acceptance region: 100 ev < Energy < 40 kev A.Münster (TUM) Direct Dark Matter Search with CRESST-III 08/08/17 11 / 18

16 CRESST-III Phase 1: Detector Module A exposure: 2.2 kg days e /γ 95 % W-recoils above 50 % O-recoils below O W acceptance region: 100 ev < Energy < 40 kev A.Münster (TUM) Direct Dark Matter Search with CRESST-III 08/08/17 11 / 18

17 CRESST-III Phase 1: Detector Module A all events accepted events conservative assumption: all accepted events are DM recoils exclusion limit: Yellin s optimum interval method A.Münster (TUM) Direct Dark Matter Search with CRESST-III 08/08/17 12 / 18

18 Detector Module A: Exclusion Limit improvement by one order of magnitude at 0.5 GeV/c 2 reach of direct DM search experiments extended to 0.35 GeV/c 2 A.Münster (TUM) Direct Dark Matter Search with CRESST-III 08/08/17 13 / 18

19 Detector Module A: Exclusion Limit 2.2 kg days 50 kg days improvement by one order of magnitude at 0.5 GeV/c 2 reach of direct DM search experiments extended to 0.35 GeV/c 2 A.Münster (TUM) Direct Dark Matter Search with CRESST-III 08/08/17 14 / 18

20 CRESST-III Phase 2 Goal: improve radiopurity by a factor of 100 All steps of CaWO4 crystal production take place at the TUM! WO3 crystal ingot CaCO3 A.Mu nster (TUM) CaWO4 m 800 g h 130 mm Ø 45 mm Direct Dark Matter Search with CRESST-III cut & polished crystal 08/08/17 15 / 18

21 CRESST-III Phase 2 Goal: improve radiopurity by a factor of 100 All steps of CaWO4 crystal production take place at the TUM! WO3 cut & polished crystal crystal ingot CaWO4 CaCO3 m 800 g h 130 mm Ø 45 mm improve radiopurity via. & chemical purification recrystallization applied to dissolved raw materials promising results as Czochralski crystal growth is cleaning process A.Mu nster (TUM) Direct Dark Matter Search with CRESST-III 08/08/17 15 / 18

22 Gram-Scale Calorimeters: Further Reduction of Threshold - Al 2 O 3 crystal (m = 0.5 g) operated above ground without shielding - achieved threshold: 19.7 ev arxiv: sensitivity to a new range of MeV-scale DM A.Münster (TUM) Direct Dark Matter Search with CRESST-III 08/08/17 16 / 18

23 Conclusion CRESST-II Phase 2 ( ) - leading sensitivity for DM particle masses below 1.7 GeV/c 2 CRESST-III Phase 1 (since 2016) - detector design optimized to search for DM particles below 1 GeV/c 2 - threshold goal of 100 ev achieved for 4 detectors - first DM analysis with partial data set of 1 detector (2.2 kg days) one order of magnitude improvement at 0.5 GeV/c 2 sensitivity extended down to 0.35 GeV/c 2 CRESST-III Phase 2 - goal: improve radiopurity - promising results achieved by purification of the raw materials for CaWO 4 crystal production A.Münster (TUM) Direct Dark Matter Search with CRESST-III 08/08/17 17 / 18

24 Thank you for your attention! A.Münster (TUM) Direct Dark Matter Search with CRESST-III 08/08/17 18 / 18

25 Backup-Slides Andrea Mu nster TUM TeVPA 2017

26 The CRESST Experiment: Setup A.Münster (TUM) Backup-Slides 08/08/17 20 / 18

27 Transition Edge Sensor (TES) Resistance [mω] R W TES 0 10 T Temperature [mk] A.Münster (TUM) Backup-Slides 08/08/17 21 / 18

28 Production of CaWO4 Powder raw materials: selected CaCO3, WO3 powders WO3 CaCO3 Solid State Reaction partially reacted CaWO4 powder CaCO3 + WO3 CaWO4 + CO2 Al2 O3 crucible dedicated furnace ( ) C 2 repetitions Precipitation Reaction WO2 4 Ca2+ Ca(NO3 )2 + (NH4 )2 WO4 CaWO4 + 2 NH4 NO3 CaCO3 and WO3 dissolved in HNO3 and NH3 quartz ware dropping into NH3 host solution CaWO4 A.Mu nster (TUM) Backup-Slides 08/08/17 22 / 18

29 Purification of Raw Materials liquid-liquid extraction coprecipitation organic solution aqueous solution solute 1 solute 2 solute 3... precipitate solute 1 solute 2 solute 3... extractant: trioctylphosphine oxide (TOPO) precipitate: CaWO 4 A.Münster (TUM) Backup-Slides 08/08/17 23 / 18

30 Crystal Growth via Czochralski Method melt CaWO4 powder in Rh crucible of Czochralski furnace lower seed crystal into CaWO4 melt draw in z direction under rotation Formation of a cylindrically shaped crystal with crystallographic orientation of seed crystal z A.Mu nster (TUM) Backup-Slides 08/08/17 24 / 18

31 Fully Scintillating Housing: Veto of Surface Backgrounds A.Münster (TUM) Backup-Slides 08/08/17 25 / 18

32 CRESST-III Phase 1: Neutron Calibration A.Münster (TUM) Backup-Slides 08/08/17 26 / 18

33 CRESST-III Phase 1: 100 ev Pulse A.Münster (TUM) Backup-Slides 08/08/17 27 / 18

34 Detector Module A: Hardware Trigger Efficiency preliminary A.Münster (TUM) Backup-Slides 08/08/17 28 / 18

35 Detector Module A: Software Trigger Efficiency typical baseline trace Analytical description of amplitude distribution in empty baselines A.Mu nster (TUM) Backup-Slides 08/08/17 29 / 18

36 Detector Module A: Software Trigger Efficiency optimum filter (Gatti-Manfredi filter) maximizes the ratio between pulse amplitude and noise RMS preliminary allow 1 count/(kg day) of noise distribution after optimum filter A.Münster (TUM) Backup-Slides 08/08/17 30 / 18

37 Yellin Methods Maximum gap method: Consider largest gap (0 events observed) Optimum interval method: Consider largest interval with certain number of events observed A.Münster (TUM) Backup-Slides 08/08/17 31 / 18