Bernard Sadoulet Dept. of Physics /LBNL UC Berkeley UC Institute for Nuclear and Particle Astrophysics and Cosmology (INPAC) Strategies for the Detection of Dark Matter What do we know? What have we achieved so far? Entering interesting domain Strategies for the future Exciting new technologies => zero background experiments cross checking each other + consistency with LHC 1 B.Sadoulet Strategies for the Detection of Dark Matter KEK 6 Feb 07
1. What do we know? Standard Model of Cosmology 2. What has been achieved? 3. Strategies for the future A surprising but consistent picture Non Baryonic Dark Matter Ω Λ Ω matter Not ordinary matter (Baryons) Ω m >> Ω b = 0.047 ± 0.006 from Nucleosynthesis WMAP Ω m h 2 ≠ Ω b h 2 ≈ 15 σ 's + internally to WMAP Mostly cold: Not light neutrinos ≠ small scale structure m v < .17 eV Large Scale structure+baryon oscillation + Lyman α 2 B.Sadoulet Strategies for the Detection of Dark Matter KEK 6 Feb 07
1. What do we know? Ongoing Systematic Mapping 2. What has been achieved? 3. Strategies for the future dark matter and energy Λ non baryonic Quintessence baryonic clumped H 2 ? ? Primordial gas Black Holes VMO Mirror branes ? exotic particles Energy in bulk dust MACHOs non-thermal thermal SuperWIMPs Light Neutrinos WIMPs Axions Wimpzillas Most baryonic forms excluded (independently of BBN, CMB) Particles: well defined if thermal (model dependent when athermal) Additional dimensions? 3 B.Sadoulet Strategies for the Detection of Dark Matter KEK 6 Feb 07
1. What do we know? Standard Model of Particle Physics 2. What has been achieved? 3. Strategies for the future Fantastic success but Model is unstable Why is W and Z at ≈ 100 M p ? Need for new physics at that scale supersymmetry additional dimensions Flat: Cheng et al. PR 66 (2002) Warped: K.Agashe, G.Servant hep-ph/0403143 In order to prevent the proton to decay, a new quantum number => Stable particles: Neutralino Lowest Kaluza Klein excitation QCD violates CP Dynamic stabilization by a Peccei-Quinn axion? Gravity is not included and we do not understand vacuum energy Always the danger of a failure of General Relativity and that dark matter is part of a new set of “epicycles” that we invent to adjust theory to increasingly accurate data 4 B.Sadoulet Strategies for the Detection of Dark Matter KEK 6 Feb 07
1. What do we know? Particle Cosmology 2. What has been achieved? 3. Strategies for the future Bringing both fields together: a remarkable concidence Particles in thermal equilibrium + decoupling when nonrelativistic Freeze out when annihilation rate ≈ expansion rate ⇒ Ω x h 2 = 3 ⋅ 10 -27 cm 3 / s ⇒ σ A ≈ a 2 2 Generic σ A v M EW Cosmology points to W&Z scale Inversely standard particle model requires new physics at this scale (e.g. supersymmetry or additional dimensions) => significant amount of dark matter Weakly Interacting Massive Particles 2 generic methods: Direct Detection = elastic scattering Indirect: Annihilation products γ ’s e.g. 2 γ ’s at E=M is the cleanest ν from sun &earth ≈ elastic scattering dependent on trapping time e + , p 5 B.Sadoulet Strategies for the Detection of Dark Matter KEK 6 Feb 07
1. What do we know? Direct Detection 2. What has been achieved? 3. Strategies for the future Elastic scattering dn/dE r Expected event rates are low (<< radioactive background) Expected recoil spectrum Small energy deposition ( ≈ few keV) << typical in particle physics Signal = nuclear recoil (electrons too low in energy) ≠ Background = electron recoil (if no neutrons) E r Signatures • Nuclear recoil • Single scatter ≠ neutrons/gammas • Uniform in detector Linked to galaxy • Annual modulation (but need several thousand events) • Directionality (diurnal rotation in laboratory but 100 Å in solids) 6 B.Sadoulet Strategies for the Detection of Dark Matter KEK 6 Feb 07
1. What do we know? Experimental Approaches 2. What has been achieved? 3. Strategies for the future A blooming field Direct Detection Techniques Ge, CS 2 , C 3 F 8 DRIFT IGEX COUPP ZEPLIN II, III CDMS XENON Ge, Si ~20% of Energy EDELWEISS Xe, Ar, WARP Ionization Ne ArDM SIGN Scintillation Phonons Heat - ~100% of Energy Few % of Energy NAIAD ZEPLIN I NaI, Xe, CRESST I Ar, Ne DAMA CRESST II Al 2 O 3 , LiF XMASS ROSEBUD DEAP !"#$ % &'()$ Mini-CLEAN *+#$ % &',- . $ / 0 At least two pieces of information in order to recognize nuclear recoil As large an amount of extract rare events from background information and a signal to (self consistency) noise ratio as possible + fiducial cuts (self shielding, bad regions) 7 B.Sadoulet Strategies for the Detection of Dark Matter KEK 6 Feb 07
1. What do we know? Phonon Mediated Detectors 2. What has been achieved? 3. Strategies for the future Principle: Detect lower energy excitations 15 keV large by condensed matter physics standards Goals • Sensitivity down to low energy Target crystal Phonons measure the full energy • 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) But: operation at very low temperature! ex: CDMS I 1999 8 6.5 cm B.Sadoulet Strategies for the Detection of Dark Matter KEK 6 Feb 07
CDMS II 1. What do we know? 2. What has been achieved? 3. Strategies for the future 7.5cmØ Ge or Si disk 1cm thick @ 35mK Athermal Phonons + ionization => large amount of information Phonon D SQUID array R bias R feedback I bias D A z C B y x Q outer Q outer Q inner Q inner V qbias 2 ionization signals (inner detector, guard) 4 phonons: Risetime and delay with respect ionization => 3D position of the event In particular, in spite of “folding”, proximity to the surface ≠ surface electrons B.Sadoulet Strategies for the Detection of Dark Matter KEK 6 Feb 07
1. What do we know? CDMS II Discrimination 2. What has been achieved? 3. Strategies for the future Ionization/Recoil energy Ionization yield Essential to fix the cuts totally Blind Surface Electrons Recoil Energy Phonon risetime and charge to phonon delay for further discrimination n n γ Risetime ( µ s) γ Surface electrons Surface electrons Yield B.Sadoulet Strategies for the Detection of Dark Matter KEK 6 Feb 07
1. What do we know? In Situ Calibrations 2. What has been achieved? 3. Strategies for the future Calibration data, prior to After timing cuts timing cuts 1.5 1.5 Z2/Z3/Z5/Z9/Z11 Z2/Z3/Z5/Z9/Z11 Ionization Yield 1.0 Ionization Yield 1.0 23x our WIMP-search background 0.5 0.5 0.0 0.0 53% acceptance of neutrons 10 20 30 40 50 60 70 80 90 100 10 20 30 40 50 60 70 80 90 100 Recoil Energy (keV) Recoil Energy (keV) Blue points: electron recoils induced by a 133 Ba γ source Yellow points: nuclear recoils induced by a 252 Cf neutron source 11 B.Sadoulet Strategies for the Detection of Dark Matter KEK 6 Feb 07
1. What do we know? WIMP-search data 2. What has been achieved? 3. Strategies for the future After timing cuts, which Prior to timing cuts reject most electron recoils 1.5 1.5 10.4 keV Gallium line Z2/Z3/Z5/Z9/Z11 Ionization Yield Ionization Yield 1.0 1.0 0.5 0.5 1 candidate (barely) 1 near-miss 0.0 0.0 Z2/Z3/Z5/Z9/Z11 0 10 20 30 40 50 60 70 80 90 100 0 10 20 30 40 50 60 70 80 90 100 Recoil Energy (keV) Recoil Energy (keV) ESTIMATE: 0.37 ± 0.15(stat.) ± 0.20(sys.) 90 kg.days electron recoils, 0.05 recoils from neutrons expected 34kg.days after cuts 12 B.Sadoulet Strategies for the Detection of Dark Matter KEK 6 Feb 07
1. What do we know? CDMS II (2005) 2. What has been achieved? 3. Strategies for the future 10 times more sensitive than any other Scalar couplings experiment Increasing tension with DAMA who claims a signal (NaI) Zeplin-I result in doubt astro-ph/0512120 See PRL 96 (2006) 011302 Ellis et al 2005 CMSSM Entering in interesting territory Adding 1st Soudan run, 53kg.day-> 19kg.day after cut Total 53 kg.day after cut 13 B.Sadoulet Strategies for the Detection of Dark Matter KEK 6 Feb 07
1. What do we know Goals: Cover Supersymmetry 2. What has been achieved? 3. Strategies for the future ZEPLIN I EDELWEISS DAMA World-best limit today ZEPLIN II goal CDMS II 2007 XENON 10 SuperCDMS 25kg 25 kg of Ge 2011 SuperCDMS Phase B 150 kg of Ge 10 -45 cm 2 SuperCDMS Phase C 1000 kg of Ge 10 -46 cm 2 10 -45 cm 2 next step 25-100kg 10 -47 cm 2 Ultimate 10 -47 cm 2 2-8 tons ≈ No background! 14 B.Sadoulet Strategies for the Detection of Dark Matter KEK 6 Feb 07
1. What do we know Why 1 Zeptobarn ≡ 10 -45 cm 2 2. What has been achieved? 3. Strategies for the future Focus Point Bulk (tan β ~10) (5 < tan β < 45) χ 2 0 , χ 1 ± Coannihilation Higgs Funnel (50 < tan β < 60) µ>0 Stau Coannihilation (tan β ~ 10) Bulk region is accessible both to LHC and Direct Detection Rich physics in region of overlap (stability, couplings) Direct Detection can access readily Focus region 10 -45 cm 2 is a natural LHC has trouble above 350GeV/c 2 scale LHC can access low cross section but fine tuning The Higgs funnel and stau coannihilation are fine tuned to enhance annihilation 15 B.Sadoulet Strategies for the Detection of Dark Matter KEK 6 Feb 07
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