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Dark Matter Detection AAPCOS 2015 DARK MATTER DETECTION Viktor Zacek, Université de Montréal Saha Institute of Nuclear Physics October 2015 • Most probably there are 10 Mio DM particles in this room • They swirl around with a speed of 500 000 km/h • About 1012 particles traverse you during this presentation • Nevertheless we do not feel them because they interact super weakly & super rarely Sun • And yet: they dominate the structure and future of the Universe! • …but what is DM and how to detect it ? Lecture I • Evidences for Dark Matter • Present knowledge of the matter content of the Universe • Dark Matter and structure of the Universe • What Dark Matter can and cannot be Lecture II • DM detection – rates and limits • Backgrounds and their mitigation • A guided tour through SNOLAB • Status of direct search experiments Lecture III • Status of indirect search experiments • Accelerator searches • Other candidate searches • Future directions THE DARK MATTER PROBLEM - FIRST INDICATIONS • Studies kinetic energies of 8 galaxies of the Coma Cluster . finds velocities are much larger than expected (virial theorem) Fritz Zwicky, 1937 . apparently Coma cluster contains 200 x more mass than is visible in form of galaxies The “hidden mass” problem becomes a “key problem” of modern cosmology DARK MATTER & GALACTIC ROTATION CURVES v2 GM(r) rot r r 2 Vera Rubin, 1974 1 v r ퟏ 풗 ∝ 풓풐풕 풓 Doppler shift of star light and of HI distribution DARK MATTER & GALACTIC ROTATION CURVES v2 GM(r) rot r r 2 Vera Rubin, 1974 ퟏ 풗 ∝ 풓풐풕 풓 For vrot = ct. M (r) must increase linearly with r For large r halos of galaxies start to overlap Doppler shift of star light and of HI distribution Mhalo > 10 x (Mlum + Mgas) DARK MATTER IN OUR MILKY WAY 1kpc = 3.259 103 Ly 2 vrotr 0.3 m /cm3 M (r) DM p G 2MASS two Micron All Sky Survey …only 5-10% of matter visible! DARK MATTER FURTHER OUT . Size of Local group 2.2 MLy . MW & M31 dominate Local Group V= 3x105 km/h . Enormous gravit. pull between the two galaxies . Invisible mass > 10 x MMW . Local group at fringe of Virgo cluster Virgo cluster v 1.6x106 km/h v 2 x 106 km/h . Size of Virgo cluster 50MLy . Local group pulled towards Virgo cluster . invisible mass > 10 x Mvis Virgo Cluster pulled towards an invisible “Great Attractor” VIRGOHI21: A GALAXY OF DARK MATTER ! (50 M Ly) Visible spectrum RF-hydrogen emission 1000 x more Dark Matter than hydrogen! M 0.1 MMW (Feb. 2005) DARK MATTER AROUND CLUSTERS OF GALAXIES Stellar mass 15% of galaxy masses Abell 2029 ( 100 Mpc) . a cluster of thousands of galaxies . surrounded by gigantic clouds of hot gas DM mass 95% of 6 . T 10 K cluster mass DARK MATTER AT AT LARGER SCALES Gravitational lensing . grav. potential causes time delay 2 of light (Shapiro) refractive index n 풏 = ퟏ − ퟐ흋/풄ퟐ 2 2 ∆ = − 훻 푛푑푙 = − 훻 휑푑푙 푐2 푐2 HST CL0024+1654 • provides evidence of large masses between source and MW • recently 3D reconstruction of clusters of Dark Matter Mdark>50 Mvis THE BULLET CLUSTER IE0657-56 ( 1 Gpc) High velocity merger of clusters of galaxies 4500 km/s 108K DM: “collision less” Mdark > 49 Mvis M. Markewitch et al: HST, Magellan, Chandra (August 2006) THE CETUS CLUSTER MACSJ0025.4 (6x109 LY) HST, Chandra (August 2008) DARK MATTER & DYNAMICS OF THE UNIVERSE m 2 E R m M = mass of Universe kin 2 R = radius of Universe mM R E G m = mass of a border pot R M galaxy v m 4 3 E pot G (v R ) R 3 Energy density of vacuum 2 v = c /8G Ekin + Epot = Etot m . GMm 1 R 2 ( mc2 R2 ) E 2 R 6 tot « Friedmann equation » adds to gravitation! THE FRIEDMANN EQUATION 1 8G A. Einstein: R g R T g 2 c4 m . GMm 1 mc2 R 2 ( mc2R2 ) E k 2 R 6 tot 2 dE pot Mm 1 2 k : curvature of space! F G 2 mc R dR R 3 k = 0: flat k > 0: closed k < 0 open attractive repulsive (Robertson-Walker metric) HUBBLES LAW & CRITICAL DENSITY v = H R Hubbles law! R(t) H(t)R(t) 0 H = 72 km s-1Mpc-1 (today!) 0 m . GMm 1 mc2 R 2 ( mc2R2 ) E k 2 R 6 tot 2 2 R 8 kc2 H (t)2 G( ) V 2 = c2/8G R 3 R v Friedmann equation 3H 2 “critical density” k = 0 (for =0) c 8G THE CRITICAL DENSITY = 0 3H 2 c 8G today: 1proton/m3 -26 3 c = 1.9 10 kg/m Mass parameter m = 0/ c =v/c 0: present day value tot m tot > 1 closed U. tot < 1 open U. tot = 1 flat, euclidean, critical U. ...but lum 0.01 ( 1!) HOW TO MEASURE ? Count all the components of the Universe! . Luminous matter, stars . DM from galaxies and their rotation curves . DM in clusters of galaxies . DM inferred from x-ray clouds around clusters of galaxies . DM from large scale flows of galaxies . DM by gravitational lensing + Measure the geometry of the Universe! EVOLUTION OF THE UNIVERSE Planck Phase transition @T 10-35s with factor x 1050 expansion space flat FAR AWAY IS LONG AGO J. Primack, G. Gelmini B FROM BIG BANG NUCLEOSYNTHESIS n + p D T + p 4 He 3He + n 4He p + D 3He D + D 4He n + D T He + T 7Li …well understood no elements A = 5 / 8 heavy elements @ T ~ 106 y Yi = fct( b, T, n, n , …) light el. abund. consistent over O(9) b = 0.04 0.007 c CURRENT EVIDENCE FOR 2003 SN Type Ia Redshift m = 0.3, = 0.7 …AND THERE IS A COSMIC COINCIDENCE ?! ~ m just now?? THE 2.7K COSMIC MICROWAVE RADIATION (CMB) 1965 accidental discovery by A. Penzias & R.Wilson (1978 NP) Perfect and isotropic black body spectrum of 2.725±0.001 K 8휋ℎ 푓3푑푓 휖 푓 푑푓 = 3 푐 푒푥푝 ℎ푓 푘퐵푇 − 1 Energy density Preservation of bb-spectrum if f &T scale with (1+z); Explains low temperature today matter & radiation @ 2K are not in equilibrium! Earlier U. very much hotter thermal equilibrium of matter & radiation CMB is a “relic radiation” which you could see as noise at home on a CTR TV!!! U. Is expanding! First proof of hot BB-theory …a revolution in cosmology THE ANISOTROPY OF THE COSMIC MW BACKGROUND Image of early Universe imprinted on temp. anisotropy of CMB WMAP 2001 T/T 10-5 Planck 2013 . 300 ky after BB photons decouple from matter T 6000 K . before decoupling: plasma oscill./ of photon-baryon “liquid” sound waves . CMB: snap shot of sound waves when rad. decoupled . Today light red shifted by 1/1000 2.7 K . Smallness of T/T visible Universe once causally connected Inflation! . Image of quantum fluctuation at 1019 GeV Angular diameter of the moon Expansion in spherical harmonics of CMB temp. field Multipole development angular scale . l number of cycles in the sky . = / l . lpeak = 200 / tot 0 . lpeak = 197 6 (0.9 ) ( Ang. size of moon: 0.50 ) Curvature of Universe: tot “Cosmic variance” (only one Universe) Baryon density small: b PLANCK RESULTS: Other : tot = 0.9890.02 Inflation : tot = 1 b = 0.049 0.007 BBN: b = 0.039 dm = 0.262 0.007 clusters of galaxies, grav. lensing hot x-ray gas : m = 0.3 = 0.69 0.02 SN1a –redshift : = 0.7 H0 = 67.31.2 km/sec/Mpc HST: H0 =72 4 km/sec/Mpc T0= 13.81 0.058 Gyr HST: 11 Gyr DM & DEVELOPMENT OF STRUCTURE • BB creates DM + ord. Matter • DM decouples early • DM clumps • Ordinary matter flows in • Galaxies form • Galaxies trace DM distribution DO GALAXIES TRACE THE DM DISTRIBUTION ? COSMOS EVOLUTION SURVEY: (Jan. 2007) - First large scale 3D reconstruction of DM distribution - HST, ESO VLT, Magellan, Subaru, XMM Newton Near infra red HST Grav. lensing DM > six times more abundant than ordinary matter 3 slices of red shift 6.5 By ago 5 By ago 3.5 By ago Growing clumpiness of DM & ordinary matter flowing in WHAT IS THE STRUCTURE AT LARGE SCALE SLOAN DIGITAL SKY SURVEY > 100 Mpc - 2.5m telescope Apache Point - 120 Megapixels - 2008 1.6 M galaxies - 2011 map covers 35% of sky WHAT KIND OF MATTER CAN EXPLAIN LSS? Baryonic matter @ t = 225s (BBN) cannot clump to form voids (200MLy) filaments & superclusters …structures thinned out by Hubble expansion Assume DM decouples earlier @ t < tBBN and interacts weakly • longer time to develop structure • baryons fall into grav. troughs • galaxy formation ok • Large scale structure ok LSS AND DARK MATTER SPEED COLD DM • non relativistic ∆푻 • non-baryonic (CMB ~ퟏퟎ−ퟓ) 푻 • weak interaction w. baryonic matter • clump on small scale HOT DM • smaller clusters first ∆푻 . non-baryonic (CMB ~ퟏퟎ−ퟓ) 푻 . relativistic . weak interaction with ord.matter . e.g. massive ’s . before decoupling structures washed out . superclusters form first cdm-hdm1-princeton.mpeg LSS AND DARK MATTER SPEED cdm-hdm1-princeton.mpeg LARGE SCALE STRUCTURE Best fit: 5% baryons 25% dark matter 70% dark energy (x) ikx 2 (x) (k)e P(k) k k The larger the scale we average the more uniform becomes the Universe! Convincing Evidence for Dark Matter at all Scales! Rotation curve Cluster kinematics Velocity flow Lensing Hot X-ray gas Bullet Cluster Large scale structure BB nucleosynthesis CMB anisotropy The Concordance Model .
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