Bernard Sadoulet Dept. of Physics /LBNL UC Berkeley UC Institute for Nuclear and Particle Astrophysics and Cosmology (INPAC) Dark Matter Searches Particle Cosmology Non baryonic dark matter (Axions) WIMPs: a generic consequence of new physics at TeV scale Direct Detection of WIMPs Noble Liquids Phonon Mediated Detectors DAMA 1 B.Sadoulet Dark Matter searches Neutrinos 2008 30 May 08
1. Particle Cosmology Standard Model of Cosmology 2. Noble liquids 3. Phonon mediated 4. DAMA A surprising but consistent picture Ω Λ NASA/WMAP Science Team 2006 Ω matter Not ordinary matter (Baryons) Ω m >> Ω b = 0.047 ± 0.006 from Nucleosynthesis χ WMAP + internally to WMAP Ω m h 2 ≠ Ω b h 2 ≈ 15 σ 's Mostly cold: Not light neutrinos ≠ small scale structure m v < .17 eV Large Scale structure+baryon oscillation + Lyman α 2 B.Sadoulet Dark Matter searches Neutrinos 2008 30 May 08
1. Particle Cosmology Standard Model of Particle Physics 2. Noble liquids 3. Phonon mediated 4. DAMA 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 3 B.Sadoulet Dark Matter searches Neutrinos 2008 30 May 08
1. Particle Cosmology Particle Cosmology 2. Noble liquids 3. Phonon mediated 4. DAMA 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 ≈ α 2 2 Generic Class σ A v M Cosmology points to W&Z scale EW 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 + Large Hadron Collider 4 B.Sadoulet Dark Matter searches Neutrinos 2008 30 May 08
1. Particle Cosmology Direct Detection 2. Noble liquids 3. Phonon mediated 4. DAMA 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) 5 B.Sadoulet Dark Matter searches Neutrinos 2008 30 May 08
1. Particle Cosmology Experimental Approaches 2. Noble liquids 3. Phonon mediated 4. DAMA 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 - y g r Few % of Energy e n E f o NAIAD % 0 0 1 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) 6 B.Sadoulet Dark Matter searches Neutrinos 2008 30 May 08
Status early 2007 1. Particle Cosmology 2. Noble liquids 3. Phonon mediated 4. DAMA Scalar coherent interaction ≈ A 2 -40 10 Cross-section [cm 2 ] (normalised to nucleon) 5 0 0 2 i S S S DATA listed top to bottom on plot -41 10 M S CDMS (Soudan) 2005 Si (7 keV threshold) I D E CRESST 2004 10.7 kg-day CaWO4 C W Edelweiss I final limit, 62 kg-days Ge 2000+2002+2003 limit L WARP 2.3L, 96.5 kg-days 55 keV threshold E D 5 ZEPLIN II (Jan 2007) result E 0 CDMS (Soudan) 2004 + 2005 Ge (7 keV threshold) 0 2 x x x Linear Collider Cosmology Benchmarks (preliminary) -42 e 10 Roszkowski/Ruiz de Austri/Trotta 2007, CMSSM Markov Chain Monte Carlos (mu>0): 68% contour G Roszkowski/Ruiz de Austri/Trotta 2007, CMSSM Markov Chain Monte Carlos (mu>0): 95% contour S M x x x Ellis et. al Theory region post-LEP benchmark points D Baltz and Gondolo, 2004, Markov Chain Monte Carlos C -43 10 -44 10 log sensitivity 1 2 3 10 10 10 WIMP Mass [GeV/c 2 ] Three Challenges s e sensitivity ∝ n s • Understand/Calibrate detectors i t i v i t • Be background free y MT ∝ much more sensitive than sensitivity ∝ constant M background subtraction T log(exposure=target mass M × time T) eventually limited by systematics • Increase mass while staying background free 7 B.Sadoulet Dark Matter searches Neutrinos 2008 30 May 08
1. Particle Cosmology Current results 2. Noble liquids 3. Phonon mediated 4. DAMA 3 examples in more details Xenon 10 as generic for CDMS as generic for ZEPLIN II ,WARP, ArDM EDELWEISS & CRESST 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 - y g r Few % of Energy e n E f o NAIAD % 0 0 1 ZEPLIN I NaI, Xe, ~ CRESST I Ar, Ne DAMA CRESST II Al 2 O 3 , LiF + New ideas XMASS ROSEBUD DEAP !"#$ % &'()$ e.g. Monroe Mini-CLEAN *+#$ % &',- . $ / 0 DAMA/Libra Nygren new modulation result 8 B.Sadoulet Dark Matter searches Neutrinos 2008 30 May 08
1. Particle Cosmology The Noble Liquid Revolution 2. Noble liquids 3.Phonon mediated 4.DAMA Noble liquids are both excellent scintillators and ionization collectors => get to large mass while maintaining excellent background by self shielding and discrimination Log (Ionization/Scintillation) Liquid Xenon Ionization + scintillation 2 breakthroughs: ✴ Extraction of electrons from the liquid to the gas ✴ At low energy, separation between electron recoils and nuclear recoils increases => work down to ≈ 4.5 photo electrons with 99% electron rejection efficiency with 50% nuclear recoil efficiency Liquid Argon (or Neon) D. McKinzey For light liquids, one additional handle : rise time Triplet (long decay time) killed by nuclear recoil 9 B.Sadoulet Dark Matter searches Neutrinos 2008 30 May 08
1. Particle Cosmology Xenon 10 2. Noble liquids 3.Phonon mediated 4.DAMA S1 ≈ 8 p.e. S2 ≈ 3000 p.e. Liquid Xenon: Scintillation + ionization two photon pulses => depth Main differences with Zeplin II: Smaller Photomultipliers Photomultipliers in liquid 10 B.Sadoulet Dark Matter searches Neutrinos 2008 30 May 08
1. Particle Cosmology Noble Liquids 2. Noble liquids 3.Phonon mediated 4.DAMA Great progress! -40 10 Cross-section [cm 2 ] (normalised to nucleon) http://dmtools.brown.edu/ Gaitskell,Mandic,Filippini DATA listed top to bottom on plot CDMS (Soudan) 2005 Si (7 keV threshold) CRESST 2004 10.7 kg-day CaWO4 Edelweiss I final limit, 62 kg-days Ge 2000+2002+2003 limit -41 WARP 2.3L, 96.5 kg-days 55 keV threshold 10 ZEPLIN II (Jan 2007) result CDMS (Soudan) 2004 + 2005 Ge (7 keV threshold) P R XENON10 2007 (Net 136 kg-d) A x x x Linear Collider Cosmology Benchmarks (preliminary) W I Roszkowski/Ruiz de Austri/Trotta 2007, CMSSM Markov Chain Monte Carlos (mu>0): 68% contour I Roszkowski/Ruiz de Austri/Trotta 2007, CMSSM Markov Chain Monte Carlos (mu>0): 95% contour N x x x Ellis et. al Theory region post-LEP benchmark points I -42 L 10 Baltz and Gondolo, 2004, Markov Chain Monte Carlos P E 080318025800 Xenon 10 2007 Z -43 10 -44 10 080318025800 1 2 3 10 10 10 WIMP Mass [GeV/c 2 ] What about our 3 challenges log sensitivity ? • Understand/Calibrate detectors ? s e • Be background free sensitivity ∝ n s i t much more sensitive than i v i t background subtraction y MT ∝ eventually limited by systematics sensitivity ∝ constant M √ T • Increase mass log(exposure=target mass M × time T) 11 B.Sadoulet Dark Matter searches Neutrinos 2008 30 May 08
1. Particle Cosmology e.g. Xenon 10 2. Noble liquids 3.Phonon mediated 4.DAMA After pattern recognition, 10 background events with 50% nuclear recoil efficiency Very nice result but: Large gap at small energy Could it be disguised threshold CDMS Why no flaring of electron at low S1? Detector used in a region 0 1 n o with no calibration n e X Large uncertainty CDMS estimate July 2007 12 B.Sadoulet Dark Matter searches Neutrinos 2008 30 May 08
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