1 / 39

Current search results ionisation, scintillation phonons, xenon, gas

Direct Searches for WIMP Dark Matter. Neil Spooner (University of Sheffield). Dark Matter and WIMPs. Current search results ionisation, scintillation phonons, xenon, gas. Under construction. Towards 1 ton and beyond. WIMP astronomy?. All matter 32%. Non-baryonic dark matter.

nellis
Download Presentation

Current search results ionisation, scintillation phonons, xenon, gas

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Direct Searches for WIMP Dark Matter Neil Spooner (University of Sheffield) • Dark Matter and WIMPs • Current search results • ionisation, scintillation phonons, xenon, gas • Under construction • Towards 1 ton and beyond • WIMP astronomy?

  2. All matter 32% Non-baryonic dark matter A dark exotic form of Energy? WIMPs Baryons 3% baryonic dark matter Stars 0.5% Three “dark” problems Composition of the Universe Contributions to W Total (100%) W0 =1 60-70% still missing

  3. WIMPS - needed by Cosmologists • CDM • Non-relativistic at decoupling • Large scale structure Relativistic particles -> Disagrees with simulated and observed clustering of matter.

  4. WIMPS - needed by Particle Physics relic particles from the Big Bang • Symmetry between fermions and bosons • Each SM particle has a ‘superpartner’ with identical quantum numbers apart from spin • A stable Lightest Supersymmetric Particle CERN - Geneva • Most important SUSY particle for DM is the Neutralino • If LSP, SUSY exists and R-parity conserved then an ideal WIMP candidate For SUSY to agree with Standard Model: Searches for charginos and squarks at LEP and Tevatron:

  5. WIMP MD MT Search Strategy Accelerator searches LHC... Indirect Searches AMANDA, ICECUBE, ANTARES, KM3, CANGARO, MAGIC, HESS, Veritas, AMS, GLAST, SuperK... Complementary to direct searches (spin dependent) but more model dependent and less sensitive for low mass, low  Direct Searches

  6. dR Kinematics dE WIMP MD MT = Ro S(E) F2(E) I(A) obs (Eor/Ro)*dR(vE,vesc)/dER total event rate (point like nucleus) Ro dR -ER/Eor event rate per unit mass e = dE Eor R incident energy Expected featureless differential nuclear recoil energy spectrum for stationary detector ---> looks like electron background recoil energy E/(E0r) kinematic factor = 4MDMT/(MD + MT)2 • Observed spectrum 10 9 8 7 6 5 4 3 2 1 0 0 1 2 3 4 5 6 7 8 9 10 WIMP Kinematics and signals • Recoil spectral shape • no multiple interactions • use of different targets (1) Nuclear recoil discrimination (2) Low background (3) Need to go underground

  7. day directional modulation ratio ~1:100 at >50 GeV 6 ~30 kms-1 600 Jun 2nd ~220 kms-1 Sun (Eor/Ro)dR/dE Earth annual modulation few %change WIMP E/(Eor) WIMP Modulation

  8. 10-5 DAMA 2003 10-6 Edel I, CDMS I, Zep I.. high/low mass galactic confirmation - annual modulation - directionality halo studies 10-7 Edel II, CDMS II, Zep II.. 2006 scale-ups 10-8 Pb 2010 10-9 1 ton ~1 event/100kg/year 10-10 1000 GeV 100 GeV 2020 100 ton ~1 event/10ton/year 10-11 barriers? • technology barriers (manufacturability/reliability) • background barrier • site barriers (depth & volume) • cost 10-12 Strategy flow chart/matrix mssm Roszkowsky et al. signal found no signal LHC: (i) no detection (still need DM, could be high mass) (ii) detection (increase drive, may refine search)

  9. WIMP Detection Techniques Ge, Si Ge LiF, Al2O3 heat ionisation BGO, CaWO4 Xe NaI, CsI, Xe light movement gas (CS2) discrimination: none, statistical, event by event

  10. Semiconductor Ge, Si, GaAs, TlBr…. • Inorganic Scintillator NaI(Tl), CsI(Tl), CaF2(Eu)... • Organic Scintillator Stilbene, plastics, liquids... Phonon (ionisation-thermal) Xenon (ionisation-scintillation) TPC (directional) • Bolometer NTD, TES…Ge, Si, LiF, sapphire…. • S/C granules • Superheated droplets • Noble gases • TPC gases …….. WIMP experiment summary LABORATORY EXPERIMENT TECHNIQUE Bern (Switzerland) ORPHEUS (SSD) Tin Superconducting Superheated Detector Boulby (UK) NAIAD NaI scintillator (50-60 kg) ZEPLIN I Liquid Xe scintillator (4 kg) ZEPLIN II/III Liquid-Gas Xe (scintillation/ionisation) (6-30 kg) ZEPLIN Max Liquid-Gas Xe1 ton detector (under development) DRIFT I/II Low pressure CS2 TPC 1m3 Canfranc (Spain) IGEX Ge ionisation detector (2.1 kg) GEDEON Ge detector in construction (4x7x2 kg) ANAIS NaI scintillators (110 kg) ROSEBUD CaWO4 and BGO scintillating bolometers (50-200 g) Frejus/Modane (France) Edelweiss Ge thermal/ionisation detectors (n x 320 g) Gran Sasso (Italy) H/M Ge ionisation detector (2.7 kg) HDMS Ge ionisation in 0.2 kg Ge well GENIUS-TF Ge in Ln-2- (42 kg) DAMA NaI scintillator (~100 kg) LIBRA NaI scintillator 250 kg (starting) Liquid Xe Liquid Xe scintillator (6 kg) CaF2 Scintillator CRESST-I Al2O3 0.262 kg CRESST-II CaWO4 scintillating bolometers (0.6-9.9 kg) CUORICINO TeO2 thermal detectors (41 kg) CUORE 1000x760 g TeO2 (under development) Kamioka (Japan) XMAS Large mass liquid Xe (R&D) Rustrel (France) SIMPLE (SDD) Superheated Droplet Detectors (Freon) Soudan (USA) CDMS-II 5 kg Ge +1 kg Si thermal/ionisation detectors Stanford (USA) CDMS-I 1 kg Ge +0.2 kg Si thermal/ionisation detectors SNO (Canada) PICASSO (SDD) Superheated Droplet Detectors (Freon) OTO (Japan) ELEGANTS V Massive NaI scintillators (670 kg) ELEGANTS VI CaF2 scintillators Apologies for those techniques and groups left out...

  11. Current status (SI) - ~10-6pb (2003/4) (UKDM) IGEX-Ge CRESST II-CaWO4 Edelweiss I-Ge ZEPLIN I-Lq Xe (UKDM) NAIAD - NaI CDMS II-Ge/Si DAMA - NaI assumes standard halo but see e.g. Copi+Krauss astr-ph/0307185

  12. Spin Dependent Limits NAIAD - NaI • Data from first 4 (non-optimal) crystals • 3800 kg.day • Pulse shape analysis Spin dependent Astro-P 19 (2003) 691 ZEPLIN I analysis underway

  13. Germanium - ionisation only Ge probably best purity, but no recoil discrimination Main Efforts on Background IGEX 2.1 kg Ge (2) 0.21 ev/kg/d/keV scale-ups --> 28-56 Kg GEDEON Heidelberg-Moscow 2.3 kg Ge (2 aim for 0.01 ev/kg/d/keV 0.05 ev/kg/d/keV Genius-TF Genius scale-ups --> 35 Kg

  14. claim evidence of WIMP detection M= 52 +10-8 GeV -N= (7.2 +0.4-0.9)x 10-6pb How can this be compatible with CDMS, EDELWEISS and ZEPLIN I, which do not see WIMPs…..? NaI - DAMA (annual modulation) • 100 kg of NaI(Tl) at Gran Sasso - 107,731 kg.d • Annual modulation analysis (no pulse shape analysis since ‘96) • 7 annual cycles analysed DAMA - NaI

  15. LEP bound: depends on GUT assumptions Halo: depends on vo - e.g. low value gives higher mass Model uncertainties Halo parameters - v0, vesc, halo structure SI, SD, mixed models, inelastic Form factors, (size of nucleus) (Helm) (I, Ge, Xe…) Quenching factors? Unknown systematics Non-SUSY candidates? SD contribution: could push region down Possibility 1 - wiggle room? e.g: Many different model assumption explored - can push allowed region around need to look at influence of this on the other new limits - HARD

  16. cts TC Other NaI/CsI experiments still could be important: Libra (DAMA), Canfranc (ANAIS), NAIAD (UKDM), ELEGANT…. Possibility 2 - systematics? e.g: Neutron modulation? • annual neutron modulation at Gran Sasso! (ICARUS note TM/03-01(2003)) • is total DAMA modulating amplitude (~0.02/kg/keV/d) similar to Gran Sasso neutron modulation? - DAMA/Gran Sasso n-flux estimate flux used ~0.9 x 10-7 n/cm2/s - BUT Boulby calculation (with lower U) = 7.3 x 10-7 (1.9 x 10-6) n/cm2/s • But also DAMA see no modulation above 6 keV (expected for neutrons?) Noise cut modulation? Energy resolution? • Energy calibration needs to be stable otherwise movement of cut position will change data rate even if total before cut is constant UKDM- AstroP. 19(2003)691 UKDMC for DM77 10 kg crystal DAMA- 10 kg (INFN/AE-00/10) Saki et al., 1 cm crystal

  17. Ionisation-thermal (2003/4) Edelweiss-I • Oct 02-Mar 03 - New exposure 13.8 kg.days >20 keV. • See some events - keep 2 and set limit. Neutron Calibration Data: 3 months Gammas Neutrons benchmark sensitivity: 1.4 x 10-6 pb

  18. Ionisation-thermal (2003/4) CDMS-I • Ge and Si ionisation+thermal; TES and NTD technology • 1998 - 1.6 kg.days Si ZIP (4 recoil events observed) • 1999-2000 - 10.6 kg.days Ge BLIP (17 nuclear recoil events observed) Shallow Stanford site (17 mwe) electrons muon veto >99.9% but expected neutron background 1-2 /kg/day See a total of 13 recoil candidates events > 10 keV Benchmark limit ~ 3 x 10-6 pb

  19. Ionisation-thermal (2003/4) • move to Soudan mine • increased use of ZIP technology CDMS-II 1 cm thick x 7.5 cm dia, photolithographic pattering • low field with segmenteed contacts to allow rejection of near edge events • collect athermal phonons • xy positioning and pulse shape analysis

  20. 2 Ionisation-thermal (2003/4) CDMS-II • first Soudan runs WIMP data for Z2,3,5 with same cuts ionisation yield calibration with 252Cf on Z2,3,5 Tower 1Previously 1/2 year run@ Stanford 90% cl Benchmark limit at 60 Gev spin-independent: 4 x 10-7 pb Helm SI form factors, A2 scaling, v0 = 220 kms-1, vE = 232 kms-1,  = 0.3 GeV c-2 cm-3 event rate is in region well below DAMA signal

  21. Scintillation+thermal (2003/4) CRESST II • simultaneous detection of scintillation and phonons (CaWO4) • 300 g detector run 28: 9.052 kg.days • separate calorimeter as light detector • new preliminary CRESST result • limited by neutron background Scale-up to 10 kg planned

  22. Ionisation Electron/nuclear recoil Excitation Xe+ +Xe Xe2+ +e- (recomb- ination) Xe* Xe** + Xe +Xe Xe2* 175nm 175nm Triplet Singlet 3ns 27ns 2Xe 2Xe Liquid Xenon

  23. Liquid Xenon • Single phase lq. Xe; 5 kg (3.2 kg fiducial) • Discrimination by pulse shape time constant ratio (TC) ZEPLIN-I (UKDM) • three 8cm, 9265Q PMTs • 4 cm Xe turrets • 30 cm liquid scintillator veto • 1.5-2.5 p.e./keV • E(rms)/E0.5 = 1.19 +/- 0.02 example of adding recoils for TC=0.5 fiducial cuts by 3-fold PMT coincidence

  24. Neutrons Gammas Benchmark limit ~ 1.1 x 10-6 pb major advance in xenon Liquid Xenon Data ZEPLIN-I (UKDM) • 293 kg.days, fXe = 0.22 (10-50 keV), TC ratio = 0.5 below 10 keV • Gamma calibration data from contemporaneous veto events Neutron Calibration tagged Am/Be 20-30 keV, TC=0.64+/- 0.04 example for 7-10 keV Ambient neutrons + 60Co 3-7 keV, TC=0.42+/-0.07 Am/Be 3-8 keV, TC 0.44+/-0.09

  25. Edelweiss II 100 lt cryostat for up to 120 detectors (36 kg Ge) LIBRA - NaI CDMS II (DAMA) 12 detectors (1.5 kg Ge, 0.6 kg Si) (250 kg) ZEPLIN II and III (UKDM) two-phase xenon (6-30 kg) In construction - 10-7-10-8pb (2005/6) (21 x 320 g) 2004 CRESST Scale-up to 10 kg planned Apologies for those techniques and groups left out...

  26. 90% nuc.rec. <3% elec.rec. @ 10keV UCLA/Torino/CERN 1 kg Xe test chamber Electroluminescence signal Electron recoil nuclear recoils electro- luminescence Primary scintillation signal primary scintillation 0 100 200keVrecoil e- recoil Xe recoil ZEPLIN II (30 kg) design based on scale-up of UCLA 1 kg test chamber ZEPLIN II/III - two phase (UKDMC + UCLA, Mexico City, Texas A&M, ITEP)

  27. Xenon XENON - Columbia et al • 10 kg two-phase underway • use of CsI photocathode • looking at 100 kg detector • thinking of 1 ton X-MASS - Japan DAMA-Xe early limits set

  28. XMASS Xenon - Japan 100 kg r&d detector, single phase possible 800 kg detector for DM search single phase, spherical geometry (--> 5p.e./keV), but background? Aiming for 20 kg detector

  29. Possibilities • GENIUS (HDMS) proposal for 100kg --> 1 tonne ? Intrinsic low background but NO discrimination and expensive (mainly bb) • LIBRA (DAMA) 250 kg now running Annual modulation (what if DAMA region ruled out), PSD not sensitive enough • Cryo-array (CDMS, Edelweiss) ideas for 1 tonne Good discrimination but difficult technology and expensive • ZEPLIN-MAX (UKDM) proposal for 1 tonne Good discrimination, simpler but less proven technology?, less expensive? But first a signal? Towards 1 Ton Detectors Motivation • To reach typical predicted ~minimum cross sections (~10-10 pb) Implications • Detector needs recoil discrimination at scaleable cost • Larger collaborations

  30. factor of 105 suppression achieved with 30 cm Lead and ~30 g/cm2 CH2 • [e.g. Boulby U, Th: 60, 130 ppb) Rock neutrons <1 rock event/ton/year possible GEANTIV 10-10 pb after 30 cm of lead shielding • with coinc. EM detection ok < 10/ton/yr • with poor veto (90%) ok < 1/ton/yr • [e.g. Boulby @ 1080 m] Muon neutrons FLUKA but Soudan - needs >99% veto (?) Sudbury - probably no need for veto <1 -neutron /ton/year possible with veto 10-10 pb salt/cavern boundary Detector neutrons • consider minimalist detector LSX: • 1.5 ton Cu @ 0.1 ppb U,Th 20 n/ton/yr (2-10 keV) 10-9 pb target (PMTs) @ 2 ppb U,Th 80 n/ton/yr (2-10 keV) GEANTIV purification best Cu (<0.05 ppb possible) upgrade readout (charge) ? significant care needed: 10-10 pb 1 ton Xenon - critical path neutron simulations, example for Large Scale Xe (LSX) (but ~same for others)

  31. non-PMT-based solution avoiding PMT background, scalable to 10 tons? charge readout (GEMs, MICROMEGAS) Pirdue Ltd. nb: Cu vessel to 8m dia. feasible Sheffield design Example 1 Ton xenon designs PMT-based may require 1000 PMTs UCLA design UKDM modular design with n/ shielding

  32. WIMP Wind 12:00h 42o Galactic WIMP Halo 0:00h (1) Achieve WIMP recoil signal --> requires usual >106 rejection • technology could also achieve first detection • -neutron suppression via sidereal modulation WIMP astrophysics (3) Determine which WIMP halo model is correct Direction sensitive detectors (2) Confirm galactic origin - forward-back recoil direction correlation with velocity through halo

  33. WIMP Wind 12:00h 42o 0:00h Scattered WIMP MC 30 WIMPs v0 g • Recoil About 100 WIMPs needed to identify standard halo CDM with DRIFT I technology Future? - Direction sensitivity Recoil flux @ 0hrs sidereal WIMP flux @ 0hrs sidereal

  34. 1 yr DRIFT I type with Xe 1 yr DRIFT I type technology halo model first signal DRIFT I type with sense DRIFT I type with no sense perfect PSD with straggling DRIFT II type Triaxial M-B Osipkov-Merritt Directional sensitivity - 10-6 - 10-10pb preliminary

  35. gamma region Is it feasible? - DRIFT I demonstrator (UKDMC + Temple, Occidental College) Example 252Cf - uncut data R2 neutrons (simulated WIMPs) Boulby Energy (NIPs) zero background assumption Technology achieves g background (<10-5) at threshold No need for Pb shielding in DRIFT I

  36. Advantages of DRIFT • Simple!? box + gas + wires + daq • no lead shielding, no cryogenics • maximum event information - control of systematics • change pressure easily (discrimination vs. directionality) • change target gas easily (CS2 + Xe, Ar.....) • can be modular (different sites?) BUT BIG (?): However, 100m x 10m x 5m excavation at Boulby = ~$300K

  37. Standard Maxwellian halo, v0=220kms-1. N-body simulations also suggest mild radial orbit bias. Triaxial - rather extreme case: p=0.72, q=0.7 Triaxial halo with p=0.9, q=0.8. Ultimate goal - WIMP astrophysics WIMP flux inputs for example halo models - assume all S (32GeV) recoils with 100GeV WIMPs. To see this needs improved technology - i.e. better PSD, larger scale

  38. Exposure, Mass 1000 ton.yr (galactic confirmation), 10,000 ton.yr (halo confirmation) Depth >4000 mwe (ignors statistical discrimination of neutrons via isotropy) go for 1 atm. (easier vessel?) (if) Gas technology 50 m track mgas readout (interpolation) 3 kg/m3 target 1cm readout plane spacing (2d/3d) diffusion subtraction Caverns 3 caverns of 2km x 10m x 5m Directional sensitivity 10-12pb (2020/30) The Ultimate Detector - VLD Very Large Drift halo sensitivity at 10-12pb Basic numbers for worst case cross section Low background components ok: Lucite, Cu, Kapton

  39. Conclusions General MSSM • recent rapid technology progress • (detection could be very soon) • so important to be ready with directionality • >10 Ton may be needed • but technology for this does look feasible, particularly with Xenon ZEPLIN I Roskowski et. al

More Related