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Strategies for the Detection of Dark Matter

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Strategies for the Detection of Dark Matter 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? Strategies for the future Strategies for the Detection f Dark Matter Hanoi 10 Aug 06 1 B.Sadoulet 1. What do we know? 2. What has been achieved? 3. Strategies for the future Standard Model of Cosmology A surprising but consistent picture Non Baryonic Λ Dark Matter Ω Ωmatter Not ordinary matter (Baryons) Nucleosynthesis Ω >> Ω = 0.047 ± 0.006 from m b WMAP Mostly cold: Not light neutrinos≠ small scale structure mv < .17eV Large Scale structure+baryon oscillation + Lyman α Strategies for the Detection f Dark Matter Hanoi 10 Aug 06 2 B.Sadoulet 1. What do we know? 2. What has been achieved? 3. Strategies for the future Ongoing Systematic Mapping dark matter and energy non baryonic Λ Quintessence baryonic clumped H2? ? gas Primordial Black Holes VMO Mirror branes ? exotic particles dust Energy in bulk MACHOs thermal non-thermal SuperWIMPs Light Neutrinos WIMPs Axions Wimpzillas Most baryonic forms excluded (independently of BBN, CMB) Particles: well defined if thermal (difficult when athermal) Additional dimensions? Strategies for the Detection f Dark Matter Hanoi 10 Aug 06 3 B.Sadoulet 1. What do we know? 2. What has been achieved? 3. Strategies for the future Standard Model of Particle Physics Fantastic success but Model is unstable Why is W and Z at ≈100 Mp? 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? -3 5 New result by PVLAS (Zavattini et al.) 1-1.5 10 eV MPQ≈ 2-6 10 GeV very low! would need a way to escape Giant limits very small experimental effect Gravity is not included and we do not understand vacuum energy Strategies for the Detection f Dark Matter Hanoi 10 Aug 06 4 B.Sadoulet 1. What do we know? 2. What has been achieved? 3. Strategies for the future Particle Cosmology Bringing both fields together: a remarkable concidence Particles in thermal equilibrium + decoupling when nonrelativistic Freeze out when annihilation rate ≈ expansion rate 3⋅10-27 cm3 / s a2 ⇒ Ω h2 = ⇒ σ ≈ Generic x σ v A M 2 A 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 + e , p dependent on trapping time Strategies for the Detection f Dark Matter Hanoi 10 Aug 06 5 B.Sadoulet 1. What do we know? 2. What has been achieved? 3. Strategies for the future Direct Detection dn/dE Elastic scattering 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) Er 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) An example Phonon mediated detectors CDMS: my own experiment, best sensitivity at the moment cf. Elena Aprile’s talk Strategies for the Detection f Dark Matter Hanoi 10 Aug 06 6 B.Sadoulet 1. What do we know? 2. What has been achieved? 3. Strategies for the future Phonon Mediated Detectors 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 Strategies for the Detection f Dark Matter Hanoi 10 Aug 06 7 6.5 cm B.Sadoulet 1. What do we know? 2. What has been achieved? 3. Strategies for the future CDMS Background Discrimination It works! Use Ionization Yield (ionization energy per unit recoil energy) to reject the 1334 Photons (external source) background 233 Electrons But (tagged contamination) 616 Neutrons (external source) Particles (electrons) that interact in surface “dead layer” of detector result in reduced ionization yield Ionization Threshold Strategies for the Detection f Dark Matter Hanoi 10 Aug 06 8 B.Sadoulet 1. What do we know? 2. What has been achieved? 3. Strategies for the future CDMS II Funded by NSF and DOE Strategies for the Detection f Dark Matter Hanoi 10 Aug 06 9 B.Sadoulet 1. What do we know? 2. What has been achieved? 3. Strategies for the future Athermal Phonon Sensor Technology quasiparticle trap Measurement of Al Collector W quasiparticle athermal phonon Transition-Edge diffusion signals maximizes Al Sensor information Si or Ge phonon s ~ 10mK Voltage biased W 4 normal ) Ω Transition-Edge Sensor ( 3 TES 2 R 1 superconducting Tc ~ 80mK T (mK) 1µ photolythography 3”Ø, 1cm thick 1 µ tungsten Strategies for the Detection f Dark Matter Hanoi 10 Aug 06 10 380µ x 60µ aluminum fins B.Sadoulet 1. What do we know? 2. What has been achieved? Large Amount of information 3. Strategies for the future SQUID array Phonon D Rbias Rfeedback I bias @50 mK D A z C B y x QQouterouter Q inner Qinner Vqbias 2 ionization signals (inner detector, guard) 4 phonons: Risetime and delay with respect ionization gives information about the 3D position of the event, in particular the proximity to the surface Strategies for the Detection f Dark Matter Hanoi 10 Aug 06 11 B.Sadoulet 1. What do we know? 2. What has been achieved? 3. Strategies for the future Athermal Phonon Advantage In addition to ionization yield ield Y Use phonon risetime and charge to phonon delay for further discrimination n n γ γ Surface electrons Surface electrons Essential to fix the cuts totally Blind Yield Strategies for the Detection f Dark Matter Hanoi 10 Aug 06 12 B.Sadoulet 1. What do we know? 2. What has been achieved? 3. Strategies for the future In Situ Calibrations Calibration data, prior to After timing cuts timing1.5 cuts 1.5 Z2/Z3/Z5/Z9/Z11 Z2/Z3/Z5/Z9/Z11 ield Y 1.0 23x our WIMP-search background 1.0 ield Y Ionization 0.5 0.5 Ionization 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 133Ba γ source Yellow points: nuclear recoils induced by a 252Cf neutron source Strategies for the Detection f Dark Matter Hanoi 10 Aug 06 13 B.Sadoulet 1. What do we know? 2. What has been achieved? 3. Strategies for the future WIMP-search data Prior to timing cuts After timing cuts, which reject most electron recoils 1.5 1.5 10.4 keV Gallium line Z2/Z3/Z5/Z9/Z11 1.0 1.0 ield ield Y Y 0.5 0.5 Ionization Ionization 1 candidate (barely) 0.0 Z2/Z3/Z5/Z9/Z11 0.0 1 near-miss 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, 34kg.days after cuts 0.05 recoils from neutrons expected Strategies for the Detection f Dark Matter Hanoi 10 Aug 06 14 B.Sadoulet 1. What do we know? 2. What has been achieved? 3. Strategies for the future CDMS II (2005) 10 times more sensitive than Scalar couplings any other 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 Adding 1st Soudan run, 53kg.day-> 19kg.day after cut territory Total 53 kg.day after cut Strategies for the Detection f Dark Matter Hanoi 10 Aug 06 15 B.Sadoulet 1. What do we know? 2. What has been achieved? 3. Strategies for the future CDMS II Reach Large background rejection margin Used for this analysis Current methods Surface events Nuclear recoils 5 Towers 5 Kg Ge, 2kg Si 5x ⇒ Run through December 2007 -44 2 2 => X 10 further 2 10 cm @ 60GeV/c Strategies for the Detection f Dark Matter Hanoi 10 Aug 06 16 B.Sadoulet 1. What do we know? 2. What has been achieved? 3. Strategies for the future Other Phonon Mediated Detectors EDELWEISS II Mounting 21x350g Ge +NTD detectors in new cryostat Most detectors: no athermal phonon rejection of surface events 7x350g Nb/Ge fast phonon CRESST II CaWO4 Scintillation + phonons Excellent rejection, no dead layer Insensitive to W recoil scintillation Strategies for the Detection f Dark Matter Hanoi 10 Aug 06 17 B.Sadoulet 1. What do we know 2. What has been achieved? 3. Strategies for the future Goals: Cover Supersymmetry ZEPLIN I EDELWEISS DAMA World-best limit today ZEPLIN 2 CDMS II 2007 XENON 10 SuperCDMS 25kg 25 kg of Ge 2011 SuperCDMS Phase B 150 kg of Ge 10-45 cm2 SuperCDMS Phase C 1000 kg of Ge 10-46cm2 10-45 cm2 next step 10-47cm2 Requires depth ≥ Gran Sasso 25-100kg Ultimate 10-47 cm2 2-8 tons ≈ No background! Strategies for the Detection f Dark Matter Hanoi 10 Aug 06 18 B.Sadoulet Requires depth≥ SNOlab 1.
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