Direct Dark Matter Searches

Transcription

1 Direct Dark Matter Searches Marc Schumann Physik Institut, Universität Zürich What is? Invisibles12, GGI Florence, June 27th

2 Dark Matter: (indirect) Evidence NASA/WMAP Particle Dark Matter Candidates: WIMP WIMP miracle Axion SuperWIMPs sterile neutrinos WIMPless dark matter Gravitino...

3 Direct WIMP Search Elastic Scattering of WIMPs off target nuclei Target Atom 3

4 Direct WIMP Search Elastic Scattering of WIMPs off target nuclei WIMP Fig: Jon Lomberg v ~ 230 km/s v ~ 230 km/s 4

5 Direct WIMP Search Elastic Scattering of WIMPs off target nuclei WIMP v ~ 230 km/s 5

6 Direct WIMP Search WIMP Elastic Scattering of WIMPs off target nuclei nuclear recoil WIMP v ~ 230 km/s Nuclear Recoil Detectable Signal 6

7 Direct WIMP Search WIMP Elastic Scattering of WIMPs off target nuclei nuclear recoil WIMP v ~ 230 km/s Nuclear Recoil Detectable Signal Gamma- and beta-particles (background) interact with the atomic electrons electronic recoil 7

8 Direct WIMP Search WIMP Elastic Scattering of WIMPs off target nuclei nuclear recoil WIMP v ~ 230 km/s Nuclear Recoil ER ~ O(10 kev) Detectable Signal Recoil Energy: N number of target nuclei ρχ/mχ local WIMP density <σ> velocity-averaged scatt. X-section Event Rate: Detector Local DM Density Physics 8

9 Dark Matter around us? How much is here? canonical value: 0.3 GeV/cm³

10 Dark Matter around us? How much is here? canonical value: 0.3 GeV/cm³

11 Dark Matter around us? How much is here? canonical value: 0.3 GeV/cm³

12 Direct WIMP Search WIMP Elastic Scattering of WIMPs off target nuclei nuclear recoil WIMP Nuclear Recoil ER ~ O(10 kev) v ~ 230 km/s Detectable Signal WIMP Expectations Recoil Energy: scalar -n interaction CMSSM: Trotta et al. CMSSM+LHC: Buchmueller et al. Event Rate: Detector 1 event/kg/yr Local DM Physics Density ρχ~0.3 GeV/c² 1 event/ton/yr 12

13 Direct WIMP Search Summary: Tiny Rates R < 0.01 evt/kg/day ER < 100 kev Argon Xenon A² m = 100 GeV/c² = 4 x cm² form factor WIMP Expectations Recoil Energy: scalar -n interaction CMSSM: Trotta et al. CMSSM+LHC: Buchmueller et al. Event Rate: Detector 1 event/kg/yr Local DM Physics Density ρχ~0.3 GeV/c² 1 event/ton/yr 13

14 Direct WIMP Search Summary: Tiny Rates R < 0.01 evt/kg/day ER < 100 kev How to build a WIMP detector? large total mass, high A low energy threshold ultra low background good background discrimination Argon Xenon A² m = 100 GeV/c² = 4 x cm² form factor WIMP Expectations scalar -n interaction CMSSM: Trotta et al. CMSSM+LHC: Buchmueller et al. 1 event/kg/yr 1 event/ton/yr 14

15 Backgrounds (mt)-1 (mt)-1/2 without background: with background: Background Sources environment: U, Th chains, K 238 U 234 Th 234m Pa 234 U 230 Th 226 Ra 222 Rn 218 Po α 232 β β α α α Muon Flux [m-2 y-1 ] Experimental Sensitivity α Th 228 Ra 228m Ac 228 Th 224 Ra 220 Rn 216 Po α β β α α and decays (electronic recoil) alphas can pose a problem α Depth [mwe] ( technology dependent) neutrons from (,n) and sf in rocks and detector parts neutrons from cosmic ray muons Electronic Recoils Nuclear Recoils (gamma, beta) (neutron, WIMPs) 15

16 Laboratori Nazionali del Gran Sasso (LNGS) XENON100 DarkSide XENON1T LNGS: 1.4km rock (3700 mwe) DAMA CRESST Other laboratories: Boulby (UK), LSM (F), Canfranc (E), Soudan (US), Sanford (US), SNOLab (CA), Kamioka (JP), Jinping (CN),... XENON100

17 World-wide Efforts Homestake/SURF LUX WIPP DMTPC SNOLAB DEAP/CLEAN PICASSO COUPP Soudan CDMS-II CoGeNT YangYang KIMS Boulby DRIFT (ZEPLIN) (NaIAD) LSM Canfranc EDELWEISS ArDM LNGS XENON DAMA/Libra CRESST DarkSide (WArP) Kamioka XMASS NEWAGE Oto PICOLON JINPING Panda-X CDEX South Pole DM-Ice 17

18 Direct WIMP Detection COUPP PICASSO SIMPLE Tracking: DRIFT, DMTPC, MIMAC, NEWAGE Phonons CDMS EDELWEISS CRESST ROSEBUD Charge CoGeNT CDEX/Texono Light XENON, ZEPLIN LUX, Panda-X ArDM, Darkside, MAX, DARWIN, LZ DAMA, KIMS DM-Ice, XMASS DEAP/CLEAN 18

19 A Avoid Backgrounds Use of radiopure materials Shielding deep underground location large shield (Pb, water, poly) active veto (µ, coincidence) self shielding fiducialization Astropart. Phys. 35, 573 (2012) Background Suppression B Use knowledge about expected WIMP signal WIMPs interact only once single scatter selection require some position resolution WIMPs interact with target nuclei nuclear recoils exploit different de/dx from signal and background Examples Scintillation Pulse Shape Charge/Light Ratio Charge/Phonon Ratio 19

20 2 Observables for Discrimination Ionization / Phonon ER ER NR NR ER ic Re co il s backgrounds tro n NR ec El Ionization BUT: surface events timing cut charge signal S2 light signal S1 Recoil Energy (kev) CDMS-II Discrimination O(10 5 ), large acceptance PRL 107, (2011) Ionization yield and Charge/Light ratio depend on de/dx discrimination ls e c oi R r l ea Nu c signal Heat XENON100 ~99.5% 50% acceptance 20

21 Plot adadped from R. Gaitskell WIMP Searches Evolution Spin-Independent Cross ~60 GeV/c² 1e 40 1e 41 1e 42 1 evt/ton/day 1e 43 1 evt/kg/year 1e 44 1e 45 1e 46 1e 47 1 evt/ton/year Year 21

22 Plot adadped from R. Gaitskell WIMP Searches Evolution 1e 40 Oroville Spin-Independent Cross ~60 GeV/c² Homestake 1e 41 HDMS 94 UKDMC HDMS 98 DAMA 98 1e 42 IGEX DAMA 00 DAMA/Libra 08 1 evt/ton/day 1e 43 1 evt/kg/year 1e 44 Crystals Ge/NaI 1e 45 1e 46 1e 47 1 evt/ton/year Year 22

23 1e 40 Oroville Spin-Independent Cross ~60 GeV/c² Homestake 1e 41 1e 42 1 evt/ton/day EDELWEISS 98 HDMS 94 UKDMC HDMS 98 IGEX DAMA 00 DAMA 98 EDELWEISS 01 CDMS I 99 CDMS I 02 Plot adadped from R. Gaitskell WIMP Searches Evolution DAMA/Libra 08 EDELWEISS 03 CRESST 11 CDMS II 04 EDELWEISS 09 1e 43 CDMS II 10 EDELWEISS 11 1 evt/kg/year 1e 44 Crystals Ge/NaI Cryogenic Detectors 1e 45 1e 46 1e 47 1 evt/ton/year Year 23

24 1e 40 Oroville Spin-Independent Cross ~60 GeV/c² Homestake 1e 41 1e 42 1 evt/ton/day EDELWEISS 98 HDMS 94 UKDMC HDMS 98 IGEX DAMA 00 DAMA 98 EDELWEISS 01 CDMS I 99 CDMS I 02 EDELWEISS 03 Plot adadped from R. Gaitskell WIMP Searches Evolution DAMA/Libra 08 WARP ZEPLIN II CDMS II 04 ZEPLIN I CRESST 11 EDELWEISS 09 XENON10 EDELWEISS 11 CDMS II 10 XENON ZEPLIN III 1e 43 1 evt/kg/year 1e 44 XENON Crystals Ge/NaI Cryogenic Detectors 1e 45 Liquid Noble Gases Xe/Ar 1e 46 1e 47 1 evt/ton/year Year 24

25 1e 40 Oroville Spin-Independent Cross ~60 GeV/c² Homestake 1e 41 1e 42 1 evt/ton/day EDELWEISS 98 HDMS 94 UKDMC HDMS 98 IGEX DAMA 00 DAMA 98 EDELWEISS 01 CDMS I 99 CDMS I 02 EDELWEISS 03 DAMA/Libra 08 WARP ZEPLIN II CDMS II 04 ZEPLIN I CRESST 11 EDELWEISS 09 XENON10 EDELWEISS 11 CDMS II 10 XENON ZEPLIN III 1e 43 1 evt/kg/year 1e 44 XENON Crystals Ge/NaI XMASS Cryogenic Detectors 1e 45 Liquid Noble Gases Xe/Ar SuperCDMS Soudan XENON100 DarkSide-50 MiniClean LUX some experiments are missing! 1e 46 1e 47 Plot adadped from R. Gaitskell WIMP Searches Evolution DEAP-3600 XENON1T 1 evt/ton/year Year 25

26 The WIMP Landscape today this talk: focus only on spin-idependent, elastic interactions SIMPLE (2011) CRESST (2011) COUPP (2012) CRESST (2007, reanalysis) ZEPLIN-III (2011) some results are missing! 26

27 Fig. adapted from M. Yamashita Light and heavy WIMPs XENON100 threshold For higher Erec, sensitivity to low mass WIMPs is higher for light targets need low threshold lower sensitivity can be (to some extent) compensated by target mass (CoGeNT: 0.33 kg, XENON100: 48.0 kg factor ~150) 27

28 The WIMP Landscape today SIMPLE (2011) CRESST (2011) COUPP (2012) CRESST (2007, reanalysis) ZEPLIN-III (2011) some results are missing! 28

29 Annual Modulation: DAMA/Libra PMTs coupled to NaI(Tl) LNGS extremely clean background necessary looks for annual modulation (~3% effect) large mass and exposure: 1.17 ton years what is here? no modulation above 6 kev DAMA finds annual 8.8 C.L. BUT: no ER/NR discrimination! Eur. Phys. J. C 67, 39 (2010) 29

30 Annual Modulation: DAMA/Libra NaI quenching factor at low E? relevant for comparison with other experiments Collar, TAUP2011 what is here? no modulation above 6 kev Phase of muon background seems to be different from DAMA modulation arxiv: = 8 kevr (Na: QF~0.25) = 22 kevr (I: QF~0.09) 30

31 CDMS-II Latest Soudan Lab, Minnesota (USA) measure charge and heat (phonons): E deposition temperature rise ΔT Science 327, 1619 (2010) Standard Analysis PRL 106, (2011) n Re co il s Low Threshold ec tro El Very good discrimination BUT: reject surface events via timing Ionization Crystals: Ge, Si cooled to few mk low heat capacity T ~ μk R l ear c u N Heat ec oi ls Leakage compatible with bg expectation similar: EDELWEISS (F) 31

32 The WIMP Landscape today SIMPLE (2011) CRESST (2011) COUPP (2012) CRESST (2007, reanalysis) ZEPLIN-III (2011) some results are missing! 32

33 CoGeNT PRL 106, (2011) p-type point contact Ge-detector, ultra low noise, very low threshold: 0.4 kevee Soudan no ER/NR discrimination, reduce surface events by risetime cut excess at lowest energies surface events =10-40 cm² bulk events 90% signal acceptance for bulk events 33

34 CoGeNT PRL 106, (2011) p-type point contact Ge-detector, ultra low noise, very low threshold: 0.4 kevee Soudan no ER/NR discrimination, reduce surface events by risetime cut excess at lowest energies low leakage high leakage surface events =10-40 cm² bulk events 90% signal acceptance for bulk events 34

35 CoGeNT p-type point contact Ge-detector, ultra low noise, very low threshold: 0.4 kevee Soudan no ER/NR discrimination, reduce surface events by risetime cut excess at lowest energies =10-40 cm² PRL 106, (2011) Recent CoGeNT news: J. TAUP old signal new background SIMPLE (2011) remaining signal CRESST (2007, reanalysis) Kopp, Schwetz, Zupan, arxiv: some results are missing! Kelso, Hooper, Buckley, arxiv:

36 CoGeNT annual modulation PRL 107, (2011) Spectrum: Rate vs Time:: modulation Stability: electronic noise trigger threshold no modulation clear modulation in 15 months data modulation up to 3 kevee (~10 kevr) decaying background CoGeNT stability not yet demonstated with DAMA standards 36

37 CoGeNT annual modulation PRL 107, (2011) Spectrum: Rate vs Time:: Stability: electronic noise trigger threshold Observations regarding the modulation e.g. Fox et al, arxiv: , also others... there is a modulation there is a significant component >1.5 kev modulation not well explained by standard Maxwellian DM halo clearhave modulation in 15events months data XENON100 should seen modulation up to 3 kevee (~10 kevr) CDMS-II should see O(1) modulation decaying background arxiv: CoGeNT stabilty not yet demonstated with DAMA standards 37

38 CDMS Annual Modulation arxiv: annual modulation analysis on NR data (with discrimination!) No modulation is found: <0.06 evt/kevnr kg day in kevnr at 99% CL Inconsistent with CoGeNT in kevee range at 98% CL CoGeNT CDMS-II m =7 GeV/c² A recent re-assesment of the low E quenching factor of Ge suggests that the whole CoGeNT region is covered by CDMS-II. Barker, Mei: arxiv:

39 The WIMP Landscape today SIMPLE (2011) CRESST (2011) COUPP (2012) CRESST (2007, reanalysis) ZEPLIN-III (2011) some results are missing! 39

40 CRESST-II Eur.Phys.J. C72 (2012) 1971 scintillating CaW04 crystals detect light (silicon on sapphire+tes) and phonons (TES) multi-target approach excellent n- discrimination 730 kg d exposure published in 2011 rather large background new run in 2012 to reduce bg ER 67 evts in WIMP ROI neutrons Pb206 recoils 40

41 The WIMP Landscape today SIMPLE (2011) CRESST (2011) COUPP (2012) CRESST (2007, reanalysis) ZEPLIN-III (2011) some results are missing! 41

42 Liquid Noble Gases: Detector Concepts Single Phase Detector Time Projection Chamber PMT pos HV gas E S1 Time Amplitude Amplitude liquid target neg HV S1 S2 Time 42

43 ZEPLIN III PLB 709, 14 (2012) 12kg LXe target 5.1 kg fiducial mass LXe dual phase detector was operated at Boulby mine (UK) science run 2011: 1344 kg x days raw exposure 8 events observed in the ROI (7-29 kevr) compatible with background expectation ZEPLIN program has come to an end 43

44 XENON100 PRL 107, (2011) Quick Facts 62 kg LXe target Dual phase TPC active LXe veto 242 PMTs LNGS (IT) Last science run: 4800 kg x d raw exposure 1471 kg x d acpt. corrected (100 GeV/c²) lowest published background of all running DM experiments 3 events observed fully compatible with background best WIMP limit over large mass range PRD 83, (2011) 44

45 XENON100 PRL 107, (2011) Quick Facts 62 kg LXe target Dual phase TPC active LXe veto 242 PMTs LNGS (IT) Last science run: 4800 kg x d raw exposure 1471 kg x d acpt. corrected (100 GeV/c²) lowest published background of all running DM experiments 3 events observed fully compatible with background best WIMP limit over large mass range PRD 83, (2011) 45

46 Nuclear Recoil Energy Scale WIMPs interact with target nucleus nuclear recoil (nr) scintillation PRL 107, (2011) ( and 's produce electronic recoils) absolute measurement is difficult measure relative to 57 Co (122keV) relative scintillation efficiency Leff: Most precise measurement with Values down to 3 kevr by CU: PRC 84, (2011) measurement principle: d iel sh n LXe n D et XENON100: take average of all existing measurements take into account uncertainty in PL analysis get real 90% CL contour (stat AND syst) 46

47 XENON100 Current Science Run run_08 decreased background lower threshold more than 2x of 2010 dark matter data much more calibration data data analysis is almost done expect new results very soon 47

48 XMASS single phase LXe detector 800kg total, 100kg fiducial mass 60% of surface covered with 642 hexagonal PMTs very high LY (~7x higher than Xe100) 20 located in Kamioka (JP) running since end of 2010; ultra low Kr85 background XMASS announced background problems (surface events on Cu and from Al ring on PMTs) in March 2012 needs more investigation 48

49 XENON1T dual phase LXe TPC 2.4t LXe ("1m³ detector") 1t fiducial mass 100x lower background than Xe m 1.9m 0.95m Low Radioactivity Photon Detectors (3, Total ~270) (self shielding, low radioactivity components) Timeline: start construction at LNGS this year Low rad. Cryostat 1.3m 49

50 XENON10 ZEPLIN-III CDMS-II achieved The Future... XENON100 DarkSide-50 XMASS LUX DEAP-3600 MiniCLEAN 50 projected XENON100 XENON1T ultimate WIMP facilities: DARWIN, MAX, LZ Note: plot contains only experiments using noble liquids 50

51 SIMPLE (2011) CRESST (2011) CRESST (2007, reanalysis) ZEPLIN-III adapted from PRL 207, (2011) Summary 51

52 Backup 52

53 XENON10 S2 only Analysis PRL 107, (2011) Fig. adapted from Astro.Part.Phys. 34, 679 (2011) trade z-position+discrimination for lower threshold 53

54 XENON10 S2 only Analysis PRL 107, (2011) Models: Sorensen/Dahl, PRD83, (2011) Bezrukov et al., Astropart.Phys. 35, 119 (2011) 12.5d data from 2006 trigger threshold at single electron level; data not used before require S2>5 e (~1.4 kev) radial cut r<3 cm, basically no z-cut 1.2 kg choosing Qy 40% higher (lower) would yield a 2x stronger (weaker) 7 GeV/c² 54

55 Criticism or Confusion? J. Collar, arxiv: Put it in the usual style... data from Manzur et al. used in analysis Predictions are due to a mistake. Xenon is not Germanium! One has to consider the electron-ion recombination and the exciton to ion ratio, which vary with E. Conclusion: only if Qy is incompatible with data and theoretical understanding one can avoid the XENON10 contraints. 55

56 Criticism or Confusion? ZEPLIN work on single electrons: Astropart. Phys. 30 (2008) 54 arxiv: J. Collar, arxiv: And put it in the usual style... ~130 e 1 e 1 e used in analysis Conclusion: only if Qy is incompatible with data and theoretical understanding one can avoid the XENON10 contraints. 56