Dark Matter. and TPC Technologies

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1 Dark Matter and TPC Technologies The Physics Case for WIMPs Status of the Field:event by event discrimination Elements of a roadmap Bernard Sadoulet Dept. of Physics /LBNL UC Berkeley UC Institute for Nuclear and Particle Astrophysics and Cosmology (INPAC) ->TPC like qualities Solid: Phonons + Ionization/Scintillation Max Information Liquids:Xe/Ar Ionization+Scintillation 3 D reconstruction Low pressure gas: Ionization +tracking Mass is essential Directionality: ultimate test of link to galaxy Dark Matter/TPC 12/20/04 1

2 The Dark side The concordance model Ω Λ Precision Cosmology Ω tot = 1.02 ± 0.02 Ω m = 0.27 ± 0.04 Ω b = ± But extravagant universe Dark Matter/TPC 12/20/04 2 Ω matter

3 Dark Matter: Input from Cosmology Mostly Cold: pressureless, non relativistic + no interactions with photons Density fluctuations start collapsing as soon as they are in the horizon Non Baryonic Ω m (LSS,CMBR,SN) 7x Ω b (BBN,CMBR) CMB alone requires non baryonic dark matter WMAP+adiabatic+flat+no tensor Ω m h 2 =0.14±0.02 >> Ω b h 2 =0.024±0.001 Comparison of CMB ΔT/T and large scale structure Not enough ΔT/T to explain large scale structure unless non baryonic dark matter Δρ/ρ keeps growing while baryons and photons are entangled Implausible efficiency of hiding baryons Massive Compact Halo Objects (MACHOs) do not appear to form the halo of our galaxy! 6σ Dark Matter/TPC 12/20/04 3

4 Input from Fundamental Physics Supersymmetry Supersymmetry remains the prime candidate to explain hierarchy: Why M W M Z M H? + quantization of gravity Unification of coupling constants at GUT scale Magnetic moment of muon: δa µ = 27 ± (e + e - ) 2-3 s evidence for new physics 19 ± (τ,e + e - ) Mass of the neutrinos provides an additional justification to Grand Unified Theory and Supersymmetry But: fundamental problems with gravity Quantization Problem of cosmological constant Is our concordance model just a construct like the epicycles? At least show that Dark Matter is not an epicycle! Dark Matter/TPC 12/20/04 4

5 Weakly Interactive Massive Particles Particles in thermal equilibrium + decoupling when nonrelativistic Freeze out when annihilation rate expansion rate Ω x h 2 = cm 3 / s σ A v σ A α 2 M EW 2 ρ χ M EW 2 T 3 M Pl Generic Class Cosmology points to W&Z scale Inversely standard particle model requires new physics at this scale (e.g. supersymmetry) => significant amount of dark matter We have to investigate this convergence! Note: not only supersymmetry Ex. Additional dimensions G. Servant Dark Matter/TPC 12/20/04 5

6 Direct Detection Elastic scattering Expected event rates are low (<< radioactive background) Small energy deposition ( few kev) << typical in particle physics Signal = nuclear recoil (electrons too low in energy) dn/de r Expected recoil spectrum Background = electron recoil (if no neutrons) E r Signatures Nuclear recoil Single scatter neutrons/gammas Uniform in detector Linked to galaxy Sun Earth Annual modulation (but need several thousand events) Directionality (diurnal rotation in laboratory but 100 Å in solids) Dark Matter/TPC 12/20/04 6

Direct Detection: Summer 1998 Initially no discrimination Ge diodes (1989: USC/PNL, UCSB/LBNL) -> Heidelberg/Moscow = most reliable limit at large mass Large NaI counters (100 kg -> 250kg

7 Direct Detection: Summer 1998 Initially no discrimination Ge diodes (1989: USC/PNL, UCSB/LBNL) -> Heidelberg/Moscow = most reliable limit at large mass Large NaI counters (100 kg -> 250kg installed in Gran Sasso!) Spin Independent (Scalar) 2.5 evt./kg/day (MT) eff =1kg.day Background limited =>Effective mass is small mass of background-less detector giving same Dark Matter/TPC 12/20/04 7

8 Background Limited! 3 fundamental strategies Aggressively tackle Statistical method Actively reject the background the background State of the art: Heidelberg Moscow Extreme proposal: GENIUS/Genino /Majorana 12m Ø liq. N 2 tank 10 4 improvement on current level Multiple scattering Pulse shape discrim. Annual modulation Large mass => simple detectors e.g. NaI Evolution? Active rejection with the best possible discrimination <= Best technology signal to noise no dead region/tails As much information as possible (TPC Like) Discrimination variable Dark Matter/TPC 12/20/ Energy (kev)

DAMA 7 years data with 100kg NaI impressive modulation Source DAMA Astro-ph/0307403 If we interpret the modulation as evidence for WIMPs In conventional halo

9 DAMA 7 years data with 100kg NaI impressive modulation Source DAMA Astro-ph/ If we interpret the modulation as evidence for WIMPs In conventional halo model + scalar scaling of matrix element Note: Incompatible with rate Heart shape + best fit close to top Half of the modulation fitted Dark Matter/TPC 12/20/04 9

nuclear recoil Combine with low field ionization measurement e.g.

10 Cryogenic Detectors Principle: Phonon mediated detectors Goals Target crystal Sensitivity down to low energy Phonons measure the full energy (no ionization yield, quenching factor) Active rejection of background: recognition of nuclear recoil Combine with low field ionization measurement e.g. CDMS I and II EDELWEISS or photon (CRESST II) More information on rare events:athermal But: operation at very low temperature! ex: CDMS I Dark Matter/TPC 12/20/ cm

11 Background Discrimination: e.g. CDMS Nuclear Recoil Recognition: Use Ionization Yield (ionization energy per unit recoil energy) to reject the background 1334 Photons (external source) Particles (electrons) that interact in surface dead layer of detector result in reduced ionization yield 233 Electrons (tagged contamination) 616 Neutrons (external source) Ionization Threshold Dark Matter/TPC 12/20/04 11

1999 Run Ge BLIP Data Set all singlescatters NR candidates Fiducial region BLIP 3 BLIP 4 BLIP 5 BLIP 6 Gamma and electron bands well separated from NR band NR candidates are truly NR s See a

12 1999 Run Ge BLIP Data Set all singlescatters NR candidates Fiducial region BLIP 3 BLIP 4 BLIP 5 BLIP 6 Gamma and electron bands well separated from NR band NR candidates are truly NR s See a total of 13 events > 10 kev ~ 1 event/kg/day Even though this event rate is in the region of the DAMA signal, cannot be WIMPs <= 4 multiple events neutrons (17 m.w.e.) Dark Matter/TPC 12/20/04 12

13 CDMS and DAMA Feb 2000 Incompatible at more than 99.98% Standard scalar interaction Standard halo velocity distribution CDMS σ DAMA claim Dark Matter/TPC 12/20/04 13

CDMS I CDMS confirms its story at shallow depth Blue curves 2000-2004 Enlargement of fiducial

story already located deep Underground, takes the lead at high mass But some events begin to

14 CDMS I CDMS confirms its story at shallow depth Blue curves Enlargement of fiducial region New detector technology (CDMSII detectors) Additional neutron moderation EDELWEISS: same story already located deep Underground, takes the lead at high mass But some events begin to appear neutrons? g-2 ZEPLIN 1 Liquid Xenon with scintillation No in situ calibration Dark Matter/TPC 12/20/04 14

15 EDELWEISS Similar technology to CDMS I Deep underground (Frejus) 30 cm parafine, 20cm Pb,10 cm Cu No active veto 2 events which limit their sensitivity (neutrons?) Dark Matter/TPC 12/20/04 15

16 Solution of surface electron problem Fundamental: Back diffusion of hot carriers in low field Partially solved by amorphous Si/Ge layer reflecting carriers Not present in ionization +scintillation (CRESST) Nearly totally solved by using athermal phonons e.g. CDMS II (Edelweiss is developing Ge-Nb film) Ge ZIP neutrons gammas Dark Matter/TPC 12/20/04 16 Surface electrons

17 CDMS II: Result with one tower In 92 days between October 11, 2003 and January 11, 2004, we collected 52.6 live days - a net exposure of 22 kg-d after cuts Below data are shown before (left) and after (right) timing cuts (yellow points are from neutron calibration) Dark Matter/TPC 12/20/04 17

New CDMS limit from Soudan Lab NO EVENTS in nuclear recoil band (one leakage event second analysis) Expect 0.7 +/- 0.35 expected leakage betas DAMA Expect 0.

18 New CDMS limit from Soudan Lab NO EVENTS in nuclear recoil band (one leakage event second analysis) Expect 0.7 +/ expected leakage betas DAMA Expect 0.05 unvetoed neutrons (1.9 muon coincident neutron) New limit ~x4 better than EDELWEISS at a WIMP mass of 60 GeV/c 2 CDMS SUF EDELWEISS CDMS Soudan 0.1 evt/kg/d Dark Matter/TPC 12/20/04 18

19 Spin Dependent Limits Preliminary (along the line of Savage et al.) C. Savage, P. Gondolo, and K. Freese, astro-ph/ CDMS 4/04 DAMA DAMA SuperK CDMS II goal Proton coupling CDMS 4/04 CDMS II goal Neutron coupling More and more difficult to accommodate DAMA in conventional models + much larger than expected in Supersymmetry Dark Matter/TPC 12/20/04 19

20 CDMS and Supersymmetry The Executive Summary CDMS II is starting to put significant limits on unconstrained minimum supersymmetry and will extend the search down by factor 20 in cross section Important: close supersymmetry complementary to Tevatron/LHC But still above the constrained minimum supersymmetry e.g. msugra Need to extrapolate to 25 or 100 kg to get in this region => additional factor Complementary to LHC Our technology is ready for extrapolation Neutrons will become a limit at Soudan => move to SNOLab (ready 2007) Dark Matter/TPC 12/20/04 20

21 SuperCDMS mass 60GeV/c 2 Dark Matter/TPC 12/20/04 21

22 CDMS II + SuperCDMS Dark Matter/TPC 12/20/04 22

23 Requirements to Make Progress Event by event recognition of nuclear recoil >10keV total Ionization + Phonons in solids: CDMS, Edelweiss Ionization + Photons in solids: CRESST in liquids: Xe (Xenon 10, Zeplin), Ar Requires TPC like 3D position resolution edges + 2 pieces of information Tracking in low pressure gas (resolution?) Dark Matter/TPC 12/20/04 23 Light e.g.? Xe still unknown at given n recoil energy purity α and field e recoil Threshold? Ionization Large mass while keeping discrimination/low background ( 39 Ar, Rn plating, Cu) Already 0.1 events/kg/day Supersymmetry physics (complementarity with LHC) Statistics! 25kg ->150kg (-> 1ton) Challenge of industrialization for Phonon Mediated Need full demonstration of Xe (with all practical problems solved) Quite challenging for TPC 100g/m 3 : R&D needed Directionality Best hope: low pressure gas TPC

24 A Personal Score Card Looking for Rare Events: Maximum amount of information Bubble chamber/tpc like quality whether in solids/liquids/low pressure gas Phonons Liquid Ionizat +Scintil Low pressure +ionizat. +scintil. Xe Ar gas TPC Threshold Excellent High A? Threshold? Threshold? Nuclear Recoil Discrimination Excellent Athermal ϕ No dead layer Ionization threshold Scintillat. threshold Tracking 3D Partial Possible Can be Can be Demonstr. excellent excellent t 0 Low Self-Shield Material? Self Low density Ar background Rn reduct Self-shield shielding Inert material Mass Industrial for 50kg Likely to scale well Expensive Directionality?? No No Yes Good Requires R&D More difficult but not necessarily impossible Dark Matter/TPC 12/20/04 24

25 Conclusions Searches for WIMPs are essential Cosmology Particle Physics and Gravitational Physics Roadmap Elastic scattering identifying event by event nuclear recoil Phonon mediated detectors are leading the pack challenge: extrapolate to 100kg/1 ton Importance => Development of other large mass technology liquid Xe is best candidate but fundamental response measurements still to be done Essential of have large mass technology ready to complement LHC (at a very small fraction of the cost) Best route to connection to galaxy is low pressure TPC: Particle Physics technology: we should be ready to make m 3 chambers + shielding if we see a signal In spite of competition first argue for our common field and need for R&D Dark Matter/TPC 12/20/04 25

Technical Specifications and Requirements on Direct detection for Dark Matter Searches

Technical Specifications and Requirements on Direct detection for Dark Matter Searches Jin Li THU/IHEP Symposium of the Sino-German GDT Cooperation 04/08/2013 Tübingen Outline Introduction Direct detection