Dark Matter: At the brink of a discovery? Particle Cosmology Non - PowerPoint PPT Presentation

Bernard Sadoulet Dept. of Physics /LBNL UC Berkeley UC Institute for Nuclear and Particle Astrophysics and Cosmology (INPAC) Dark Matter: At the brink of a discovery? Particle Cosmology Non baryonic dark matter WIMPs: a generic consequence of new physics at TeV scale Direct Detection of WIMPs Current status 2007 : entering the interesting region 10 -44 cm 2 /nucleon Next generation of experiments ≈ 5 years: 10 -45 cm 2 /nucleon Longer term 10 -46-47 cm 2 /nucleon: next ten years? Complementarity with accelerators and indirect Large Hadron Collider 2008-2012 critical tests of our ideas GLAST Jan 08-2013 could be smoking gun B.Sadoulet Dark Matter 100 years of Cosmology 31 August 07

1. Particle Cosmology Status of Cosmology 2. WIMPs: Recent results 3.10 -44 cm 2 /nucleon 4.10 -45 cm 2 LHC/GLAST Fantastic progress! => Successful parametrization But we do not understand the fundamental physics The nature of Dark Matter? TeV scale physics? The nature of Dark Energy? Quantum aspects of gravity? The origin of inflation? Grand Unification scale physics? The Baryon and Antibaryon asymmetry? B.Sadoulet 2 Dark Matter 100 years of Cosmology 31 August 07

1. Particle Cosmology Standard Model of Cosmology 2. WIMPs: Recent results 3.10 -44 cm 2 /nucleon 4.10 -45 cm 2 LHC/GLAST A surprising but consistent picture Non Baryonic Dark Matter Ω Λ Ω matter Not ordinary matter (Baryons) � m >> � b = 0.047 ± 0.006 from Nucleosynthesis WMAP + internally to WMAP � m h 2 � � b h 2 ��� � 15 � 's Mostly cold: Not light neutrinos ≠ small scale structure m v < .17 eV Large Scale structure+baryon oscillation + Lyman � B.Sadoulet Dark Matter 100 years of Cosmology 31 August 07

1. Particle Cosmology Standard Model of Particle Physics 2. WIMPs: Recent results 3.10 -44 cm 2 /nucleon 4.10 -45 cm 2 LHC/GLAST 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 B.Sadoulet Dark Matter 100 years of Cosmology 31 August 07

Particle Cosmology 1. Particle Cosmology 2. WIMPs: Recent results 3.10 -44 cm 2 /nucleon 4.10 -45 cm 2 LHC/GLAST Bringing both fields together: a remarkable concidence Particles in thermal equilibrium + decoupling when nonrelativistic Freeze out when annihilation rate � expansion rate Generic Class � � x h 2 = 3 � 10 -27 cm 3 / s � � A � � 2 � A v 2 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 B.Sadoulet Dark Matter 100 years of Cosmology 31 August 07

1. Particle Cosmology Direct Detection 2. WIMPs: Recent results 3.10 -44 cm 2 /nucleon 4.10 -45 cm 2 LHC/GLAST Elastic scattering Expected event rates are low dn/dE r (<< radioactive background) Small energy deposition ( ≈ few keV) Expected recoil spectrum << typical in particle physics Signal = nuclear recoil (electrons too low in energy) ≠ Background = electron recoil (if no neutrons) Signatures E r • Nuclear recoil: Basic discrimination methods • 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) B.Sadoulet Dark Matter 100 years of Cosmology 31 August 07

1. Particle Cosmology Experimental Approaches 2. WIMPs: Recent results 3.10 -44 cm 2 /nucleon 4.10 -45 cm 2 LHC/GLAST A blooming field At least two pieces of information in order to recognize nuclear recoil As much information extract rare events from background As large a signal to noise ratio as (self consistency) possible + fiducial cuts (self shielding, bad regions) B.Sadoulet 7 Dark Matter 100 years of Cosmology 31 August 07

1. Particle Cosmology The overall picture 2. WIMPs: Recent results 3.10 -44 cm 2 /nucleon 4.10 -45 cm 2 LHC/GLAST Generically: scalar interactions ≈ A 2 Current WIMP searches GLAST launched early 08 Next generation 1 generation beyond Large Hadron Collider Finer and finer tuning to get right density! B.Sadoulet 8 8 Dark Matter 100 years of Cosmology 31 August 07

1. Particle Cosmology Current results 2. WIMPs: Recent results 3.10 -44 cm 2 /nucleon 4.10 -45 cm 2 LHC/GLAST 2 examples in more details Xenon 10 as generic for CDMS as generic for ZEPLIN II ,WARP, ArDM EDELWEISS & CRESST Challenges Calibration Efficiency/Threshold Background rejection B.Sadoulet 9 Dark Matter 100 years of Cosmology 31 August 07

1. Particle Cosmology 7.6 cm x 1 cm =250g Ge CDMS II 2. WIMPs: Recent results 3.10 -44 cm 2 /nucleon 4.10 -45 cm 2 LHC/GLAST Phonons+ionization large signal to noise (cf EDELWEISS, CRESST) ⇒ total energy, ionization yield: discrimination of nuclear recoils 50mK operation Athermal => large amount of information => 3D position of the event In particular, in spite of “folding”, proximity to the surface ≠ surface electrons B.Sadoulet 10 Dark Matter 100 years of Cosmology 31 August 07

1. Particle Cosmology Multidimensional Discrimination 2. WIMPs: Recent results 3.10 -44 cm 2 /nucleon 4.10 -45 cm 2 LHC/GLAST Ionization yield Timing -> surface discrimination Ionization/Recoil energy Surface Electrons Recoil Energy Newer analysis Fix cuts blind ( with calibration sources) Fix cuts blind ( with calibration sources) to get ≈ 0.5 events background to get ≈ 0.5 events background 53% nuclear recoil efficiency Expected backgrounds: 0.37 ± 0.15(stat.) ± 0.20(sys.) electron recoils, 0.05 recoils from neutrons expected B.Sadoulet 11 Dark Matter 100 years of Cosmology 31 August 07

1. Particle Cosmology CDMS II (2005) 2. WIMPs: Recent results 3.10 -44 cm 2 /nucleon 4.10 -45 cm 2 LHC/GLAST 10 times more sensitive than any other expt. in 2005 Scalar couplings Increasing tension with DAMA who claims a signal (NaI) 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 B.Sadoulet Dark Matter 100 years of Cosmology 31 August 07

1. Particle Cosmology Xenon 10 2. WIMPs: Recent results 3.10 -44 cm 2 /nucleon 4.10 -45 cm 2 LHC/GLAST S1 ≈ 8 p.e. S2 ≈ 3000 p.e. Liquid Xenon: Scintillation + ionization two photon pulses => depth Breakthrough: extraction of electrons from liquid importance of having photon detector at the bottom + high spatial resolution => better sensitivity than ZEPLIN II B.Sadoulet Dark Matter 100 years of Cosmology 31 August 07

1. Particle Cosmology Rejection Xenon 10 2. WIMPs: Recent results 3.10 -44 cm 2 /nucleon 4.10 -45 cm 2 LHC/GLAST Good rejection down to 4.5 keV nuclear recoil With 4 p.e! Why no flaring of electrons at low energy? Should be there from photoelectron statistics 6.7- 9.0 keV nuclear recoil equivalent energy Astro-ph/0706.0039 B.Sadoulet 14 Dark Matter 100 years of Cosmology 31 August 07

1. Particle Cosmology Low background running 2. WIMPs: Recent results 3.10 -44 cm 2 /nucleon 4.10 -45 cm 2 LHC/GLAST Events with depressed S2 Region where ionization is not collected After pattern recognition, 10 background events with 50% nuclear recoil efficiency Astro-ph/0706.0039 B.Sadoulet 15 Dark Matter 100 years of Cosmology 31 August 07

1. Particle Cosmology Xenon 10 Results 2. WIMPs: Recent results 3.10 -44 cm 2 /nucleon 4.10 -45 cm 2 LHC/GLAST Very nice result Large gap at small energy Demonstration of S. Yellin CDMS analysis code power of the technology • Statistically lucky? Also ZEPLIN II • Characteristics of background? • Or disguised threshold? non flaring of e recoils I I N I 5 L 0 P 0 E Z 2 S M Detector used in a region D C with no calibration 7 0 0 d Large uncertainty 2 e t 0 c 1 e CDMS estimate July 2007 p n x o e n e 7 New calibration this summer X 0 0 2 S M D C CDMS run 123+ 124 653kg days Blind analysis Expect to be background free If true, about 7 x Xenon10 3 10 -44 cm 2 /nucl @ 60GeV/c 2 discovery potential! B.Sadoulet 16 Dark Matter 100 years of Cosmology 31 August 07