Listening for the Dark Harry Nelson UCSB

Plan Massive Dark Matter Direct Detection Xenon CDMS Future 9/15/05 Penn State Colloquium

`We Declare a New Order’ (Joel Primack) Metals (us) 0.01% Visible Baryons 0.5% Dark Baryons 5% Cold Dark Matter (WIMPs?) 25% Cosmological Constant  70% `We Declare a New Order’ (Joel Primack) 9/15/05 Penn State Colloquium

Point out r, v, they tell you about central force and hence mass distribution. Use astrojax to demonstrate: 2 points: v up, F up; can study by v(r). v; = v/c r 9/15/05 Penn State Colloquium

Identfy axes… for the eight planets inner planet… just grabbed velocity data, nothing special. Equation assumes all mass is concentrated at the center. 9/15/05 Penn State Colloquium

The power law indicates all mass in Solar System is indeed all concentrated at center. *Level* indicates value of the mass at the center. b = 0.488 ± 0.009 a  M = (1.85 ± 0.06) 1030 kg 9/15/05 Penn State Colloquium

Stars w/r Galaxy Center: v/c =  constant  0.7 10-3 Repeat for other systems… moons of Saturn, all mass at center by power law, mass of saturn much less by level… Galaxy power law wrong, showing mass not at center. Use Gauss’s law to fix up, assume spherical symmetry. Level gives local mass *density*, about 2/3 p/cm^3, ½ luminous, ½ dark. Msun = (1.85 ± 0.06) 1030 kg Planets about sun MSaturn = (5.5 ± 0.2) 1026 kg Moons about Saturn 9/15/05 Penn State Colloquium

Galactic Dark Matter R is the distance from center v v is the speed (tangential) R is the distance from center 9/15/05 Penn State Colloquium

What about our home galaxy (Milky Way)?  v R  220 km/s Honma and Sofue, 1996 :v0=180 km/s Without the Dark Halo (Binney & Tremaine) 9/15/05 Penn State Colloquium

Milky Way: mainly a dark cloud Bulge Disk Sun: moves in plane of disk v/c =  0.7 10-3 Maxwellian/Gaussian (simple) v/c =  0.7 10-3 Particles in `halo’: 3-d  = mc2  n  1/3 GeV/cm3 (1/2 of total mass density) Use Bowling Ball. Our galaxy like a fried egg, rotating like a compact disk inside, at 0.7/1000 speed of light. Dark matter at rest on average; we plow through. Mass density is product of mass/particle * number density… raise mass/particle, lower needed number density. DM must move so as not to collapse at center… simplest is Maxwellian, *helps* experimentation. 9/15/05 Penn State Colloquium

Design a Particle and an Experiment 0 v/c =  0.7 10-3 v/c =  0.7 10-3 We use Germanium, A=73, mc2=67.6 GeV; others: Si, S, I, Xe, W Neutral: cool particles neutral – , n, , K0, Z0, H0… Chi^2… lightest superpartner… although not the only possibility. Weak scale is about the mass of the W and Z bosons, some new physics keeps the Higgs light. 100 GeV is `Massive’ ER½ mGec2 2  ½ 68 GeV  ½  10-6  20 keV  x-ray energy ! Easy! Massive: Mc2100 GeV hinted at by accelerator data `Weak Scale’ 9/15/05 Penn State Colloquium

Arguments for  characteristic of weak interaction Particle physics… chose Mc2  100 GeV, `Weak Scale’ Big Bang… independently implies weak cross section as well… Coincidence(s)… or Clues ??? *Big Bang*… weak cross section is just what needed to describe observed ratio of luminous to dark matter, if luminous and dark were once in thermal equilibrium. 9/15/05 Penn State Colloquium

What is the weak interaction cross section? Donald H. Perkins, 1987 Note that this is cross section per proton for inverse beta decay. Note the 100 light years! 9/15/05 Penn State Colloquium

Rate governed by scattering cross section,  Flux… get from density and velocity. Cross section converts the rest into an observable rate.. 9/15/05 Penn State Colloquium

Coherence, density of states enormous bonus! Scattering off a proton…. …. Hopeless! 0 Indistinguishable A = # neutrons + # protons Back to rate… traditional to quote cross section per *nucleon* (either proton or neutron). Really use a bag of nucleons, so must add up effects of all… add amplitudes *then* square. Also win due to density of states (for very massive wimps). Huge bonus!! Now doable. Density of States: 9/15/05 Penn State Colloquium

Rate of Main Background Move on to background… as example, consider radioactivity of person at 2 meters… turns out hard to beat! DAMA lives with large background, but uses a huge target mass (100 kg, now upgrading to 250 kg) to boost signal, and then looks for temporal modulation at an expected frequency. CDMS, other limit, tries to distinguish electron recoil background from nuclear recoil background… very small mass. (1-10 kg). Rate about 103 / (kg-day) !!! Shield… but that radioactive too Strategies: DAMA… huge target mass (100 kg), look for astrophysical modulation CDMS… small target mass (few kg) distinguish electron from nucl. recoil 9/15/05 Penn State Colloquium

0 Signal Shape Er MWIMP=100 GeV   10-42 cm2/nucleon A2 Nucleus Silicon, Sulphur Germanium Iodine, Xenon Nucleus Recoils Er Slope: Maxwell-Boltzmann WIMPs in Galaxy Diffraction 0 9/15/05 Penn State Colloquium

Catalog of Direct Detection Experiments Indirect Detection: Super-Kamiokande, Amanda, Ice-Cube, HEAT, GLAST, Egret… Look for astrophysical neutrinos, gammas From WIMP annihilation Mine, Name of experiment, technique… mostly particle/nuclear physics detectors, mass, status… mostly non-US world effort.. Note DAMA, NaI (they have evidence for a signal!), CDMS (us)… we operated at Stanford, not deep, for many years; now deep at Soudan. 9/15/05 Penn State Colloquium

Direct Detection: Signal and Main Background  v/c  0.3 Electron Recoils Background Sparse Energy Deposition Er Nucleus Recoils Er v/c  710-4 dense energy deposition efficiency low distinct energy scale 0 (calibrate: neutron) Differences the Basis of Particle ID 9/15/05 Penn State Colloquium

ZEPLIN II, III, MAX, XMAS, XENON IGEX, DRIFTI, II CDMS, EDELWEISS phonons H ionization Q scintillation L ZEPLIN II, III, MAX, XMAS, XENON NAIAD, ZEPLIN I, DAMA CRESST I, PICASSO, COUPP CRESST II, ROSEBUD Tim Sumner 9/15/05 Penn State Colloquium

E. Aprile et al., arXiv:astro-ph/0503621 Tim Sumner Xenon – nuclear recoils give 1/7 scintillation/energy, compared to electron recoils (``quenching’’)…. Sets recoil energy scale E. Aprile et al., arXiv:astro-ph/0503621 – Bernabei et al. – Arneodo et al. – Akimov et al. – Aprile et al. – LIP work Lindhard Hitachi Tim Sumner 9/15/05 Penn State Colloquium

Zeplin 1 – Scintillation Alone Nucl. Recoil Zeplin 1 – Scintillation Alone Electron Recoil 125 keV 30 keV 30 keV Nuclear Recoils – Faster Risetime… 3.2 kg Xe Risetime (ns) 9/15/05 Penn State Colloquium

Zeplin-I Limit- Background Weakens 300 kg-days CDMS: 100 kg-days 10-42 cm2 9/15/05 Penn State Colloquium

2-Phase (Liquid/Gas) Noble … Ar or Xe Nuclear Recoil S1 S2 S2 Electron Recoil S2 S1 S1 9/15/05 Penn State Colloquium

Preliminary Preliminary 9/15/05 Penn State Colloquium Gamma + neutron source Gamma source Zeplin-II Zeplin-II Preliminary Preliminary XENON 9/15/05 Penn State Colloquium Aprile et al. 2005

However, unforeseen backgrounds are the rule as sensitivity increases Analysis…. Appears scalable However, unforeseen backgrounds are the rule as sensitivity increases Promising… ZEPLIN-II and Xenon-10 soon deployed in deep sites 9/15/05 Penn State Colloquium

CDMS: Adapt Traditional Ionization Detector 0 ER10’s keV Holes e- Electrode Implants E  1 cm One of our detectors (now 30 in operation)… also use Silicon as a control. Key is to compare rate of expected signal and rate of expected background. Germanium (or Silicon) 7.6 cm ¼ kg (1/10 kg) What rate? (in, say, 1kg) Backgrounds? ….…. Gamma rays, neutrons, surface beta-decay 9/15/05 Penn State Colloquium

Our Hunting Ground Weakly Interacting Experiment Massive Particle Experiment CDMS (shallow) DAMA (old!) 1/10 9/10 Theory SUSY, various constraints including Big Bang Review the scales… cross section is *per nucleon* on vertical. Note WIMP acronym. Theoretical predictions are colored areas, the result of adaptation of various SUSY descriptions… until SUSY seen (if seen), lots of free parameters… lower cutoff from LEP. Experiments… DAMA is 3 sigma region… now 6 sigma. CDMS is limit, 9/10 chance below, prior to move to deep site. Nature of curve: most sensitivity when mass of target is about that of projectile (use Oddballs). Sensitivity loss at low mass from bad kinematics (demonstrate with small bouncy ball colliding with oddball). Sensitivity loss at high mass due to reduced number density needed to obtain given mass density. Gaitskell/Mandic 9/15/05 Penn State Colloquium

DAMA – Exploit Annual Modulation Signal: higher rate in June, lower in December Background: constant in time DAMA exploits the motion of earth relative to sun… sun hurtles along with galactic disk at about 7/1000 speed of light, but earth is simultaneously swining around (consider running with astrojax!). More energy available in June, more events above threshold. Background should be constant, but… is it really? 9/15/05 Penn State Colloquium

CDMS Collaboration (Mar. 2002) In the deep Soudan mine; 3 ignore DOE safety regs (MINOS under construction, hard hats required, not steel toed boots though). 9/15/05 Penn State Colloquium

CDMS Collaboration Brown University M.J. Attisha, R.J. Gaitskell, J-P. F. Thompson Case Western Reserve University D.S. Akerib, P. Brusov, C. Bailey, M.R. Dragowsky, D.D.Driscoll, S.Kamat, A.G. Manalaysay, T.A. Perera, R.W.Schnee, G.Wang University of Colorado at Denver M. E. Huber Fermi National Accelerator Laboratory D.A. Bauer, R. Choate, M.B. Crisler, R. Dixon, M. Haldeman, D. Holmgren, B. Johnson, W.Johnson, M. Kozlovsky, D. Kubik, L. Kula, B. Lambin, B. Merkel, S. Morrison, S. Orr, E.Ramberg, R.L. Schmitt, J. Williams, J. Yoo Lawrence Berkeley National Laboratory J.H Emes, R. McDonald, R.R. Ross, A. Smith Santa Clara University B.A. Young Stanford University P.L. Brink, B. Cabrera, J.P. Castle, C.L. Chang, J. Cooley, M. Kurylowicz, L. Novak, R. W. Ogburn, M. Pyle, T. Saab, A. Tomada University of California, Berkeley J. Alvaro-Dean, M.S. Armel, M. Daal, J. Fillipini, A. Lu, V. Mandic, P.Meunier, N. Mirabolfathi, M.C.Perillo Isaac, W. Rau, B. Sadoulet, D.N.Seitz, B. Serfass, G. Smith, A. Spadafora, K. Sundqvist University of California, Santa Barbara R. Bunker, S. Burke, D.O. Caldwell, D. Callahan, R.Ferril, D. Hale, S. Kyre, R. Mahapatra, J.May, H. Nelson, R. Nelson, J. Sander, C.Savage, S.Yellin University of Florida L. Baudis, S. Leclerq University of Minnesota J. Beaty, P. Cushman, L. Duong, A. Reisetter Cryogenic Dark Matter Search Bold faced names… those who have grown sufficiently unproductive. 9/15/05 Penn State Colloquium

Nuclear Recoil bad at making Ionization Holes e- Nuclear recoil goes at a velocity small compared to the typical electron velocity… electron wavefunction adiabatically distorts, about 1/3 the ionization. Electron recoil (Compton scatter) at a velocity exceeding typical electron velocity in Ge orbital wavefunction, sudden approximation, good ionization efficiency. Germanium more ionization! Need a second, `fair’ measure of deposited energy… sound!  0 Both deposit, say, 20 keV 9/15/05 Penn State Colloquium

Our Detectors `Phonon sensor (4)’ (TES) Array of Transition Edge Sensors Ionization Electrodes (2) x-y-z imaging: from timing, sharing Transition edge sensor to detect phonons (phono-cathode), read out with SQUIDS. Segmentation of 4… allows x-y imaging, parallel to face. Other side has ionization electrodes, segmented into edge and inner; allows rejection of edge events. Z from timing… `ZIP’… 50 mK. Z-coordinate, Ionization, Phonons ZIP Operate at 0.050 Kelvin 9/15/05 Penn State Colloquium

Transition-Edge Sensor (TES) The Phonon Sensor Al quasiparticle trap Al Collector W Transition-Edge Sensor (TES) Ge or Si quasiparticle diffusion phonons Cooper Pair Phonon impinge on thick aluminum, bust cooper pairs, quasiparticles diffuse to edge, where they heat a tiny piece of W kept on edge between normal and superconducting. Resistance goes up, read off current change. superconducting normal T (mK) Tc ~ 80mK RTES () 4 3 2 1 ~ 10mK R. Schnee 9/15/05 Penn State Colloquium

Pulses 20 KeV Phonon (4) Charge (2) Pulse readout…2 charge electrodes, 4 phonon. Phonon pulses slower, use intercomparison of pulseheights to image. Lots of information in timing. 300 300 Time (s) Time (s) 30 -30 -30 30 -30 30 9/15/05 Penn State Colloquium

Separation of the types of recoils (electron recoils) Neutrons cause nuclear recoils too! Another background… Hold up gamma source, vertical scale is ionization/phonons, vertical just phonons. Then hold up neutron source, making nuclear recoils… see the difference. But realize, neutrons are irreducible background! Go deep underground to evade! (nuclear recoils) Sound 9/15/05 Penn State Colloquium

SUF Run 21 Germanium – Low Threshold 1.3 keV x-ray, L-shell Capture Shallow Site Neutron Background 10.4 keV Ga x-rays from 71Ge K-shell Capture R. Bunker 9/15/05 Penn State Colloquium

Background Neutrons from Cosmic Ray Muons Muons from cosmic rays bust up nucleus, eject neutrons which go a long way, hard to shield with local shielding… go deep. Limited our earlier results…moved to a deep mine 9/15/05 Penn State Colloquium

Go Deep Underground to Evade Muons Vertical… muons/m^2/year, two horizontals, depth in feet for rock, meters water equivalent. Soudan shallow among deep sites… DUSEL… 6500 mwe… San Jacinto attractive. 9/15/05 Penn State Colloquium

Deep Facility Can take a canoe to Canada from Soudan. Soudan Mine Hosts: State of Minn., U Minn., Fermilab 690 meters underground 2090 meters water equivalent 9/15/05 Penn State Colloquium

Down deep in the Soudan mine General view of our cavern… electronics above clean room. HVAC Mechanical RF-shielded Clean room Shield Fridge Front-end Electronics Mezzanine Detector Prep DAQ/Electronics Clean Benches Icebox Pumps, Cryogenics Soudan II MINOS connecting tunnel 9/15/05 Penn State Colloquium

Outside In lead plastic scintillators Inside clean room… surrounded by scintillators to detect and allow removal of any particles that might have induced background… WIMPs totally silent. Cross section, photo during assembly. outer polyethylene ancient lead inner polyethylene 9/15/05 Penn State Colloquium

A Cold Heart Results from first… ZIP 1 (Ge) ZIP 2 (Ge) ZIP 3 (Ge) ZIP 4 (Si) ZIP 5 (Ge) ZIP 6 (Si) 4 K 0.6 K 0.06 K 0.04 K SQUID cards FET cards 14C The very heart… lots of copper cans at various temperatures. poorer resolution Two `towers’ 6 detectors… 10 cm 4 Germanium (0.25 kg each), 2 Silicon (0.1 kg each) 9/15/05 Penn State Colloquium

 Calibration (133Barium) (e recoils) Phonons Ionization Hold up gamma source… Barium peak in ionization, both data and MC… phonons have less resolution. L. Baudis Energy, KeV 9/15/05 Penn State Colloquium

Better Source, Calibration Ionization Phonons 9/15/05 Penn State Colloquium

n Calib. (252Californium) (nuclear recoils) Hold up neutron source, phonon energy. Germanium on left... Reconstructed recoil energy, KeV S. Kamat 9/15/05 Penn State Colloquium

Soudan Data First Run Second Run Two runs! 92 calendar days 53 live days, 1 kg Germanium Tower 1 Second Run Two runs! 140 calendar days 74 live days, 1.5 kg Germanium 0.6 kg Silicon Double `Exposure’ 9/15/05 Penn State Colloquium

Reject Multiple Interactions ZIP 1 (Ge) ZIP 2 (Ge) ZIP 3 (Ge) ZIP 4 (Si) ZIP 5 (Ge) ZIP 6 (Si) 4 K 0.6 K 0.06 K 0.04 K SQUID cards FET cards 14C n,  Backgrounds often do 0 WIMPs don’t scatter twice Ignore multiple interactions. 9/15/05 Penn State Colloquium

First Run After timing cuts, which reject external electrons Prior to timing cuts Nuclear Recoils induced by a neutron source 10.4 keV Gallium line External e (address with timing cuts) B. Cabrera 9/15/05 Penn State Colloquium

External e : surface events, ionization missed  decay contamination, escaping compton recoils Ionization not collected Electrode Implants E  z `ZIP’ : `reconstruct’ z with start time, risetime Germanium 9/15/05 Penn State Colloquium

0 External e  decay contamination, escaping compton recoils Edge Induces Phonon Energy Downshift Phonon Sensors 0 Eventually energy low, pathlength long, `phonons go ballistic’ Distinct Sensor Sharing Lower Energy Phonons Have Longer Pathlength, Diffuse More Promptly Primary Phonons `High Energy,’ `Rayleigh Scatter’ so they diffuse + energy downshift 9/15/05 Penn State Colloquium

Timing rejects surface/external e Nuclear Recoils e External e 9/15/05 Penn State Colloquium

WIMP search data with Ge detectors Z2, Z3, Z5 After timing cuts, which reject external electrons Prior to timing cuts Nuclear Recoils induced by a neutron source 10.4 keV Gallium line B. Cabrera (yellow points are from neutron calibration) 9/15/05 Penn State Colloquium

All the features on one plot Z2, Z3, Z5 10.4 keV Gallium line Surface Rejection: Omitted Applied  Energy Estimate Corrected (non-blind) 10 keV threshold (1 20 keV) 0.7  0.35 external e, 0.07 recoils from neutrons expected 2/3 event expected from Barium calib 9/15/05 Penn State Colloquium

Second Run – twice the exposure After timing cuts, which reject most electron recoils Prior to timing cuts 1.5 1.0 0.5 0.0 10.4 keV Gallium line 1.5 1.0 0.5 0.0 Z2/Z3/Z5/Z9/Z11 Ionization Yield Ionization Yield 1 candidate (barely) 1 near-miss 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 0.20 (sys.)  0.15 (stat.) surface electron recoils, 0.05 recoils from neutrons expected 9/15/05 Penn State Colloquium

Limits DAMA 9/15/05 Penn State Colloquium

PRELIMINARY The Near Future Improvements 30 detectors in 5 towers of 6 Installed 3 additional towers November 2004 CDMS- Soudan CDMS -projected Edelweiss ZEPLIN-1 PRELIMINARY Improvements Cryogenics, backgrounds, DAQ Currently commissioning 30 detectors in 5 towers of 6 4.75 kg of Ge, 1.1 kg of Si to run through 2006 Improve sensitivity x10 Last fall we installed 18 additional detectors in 3 additional towers, for a total of 4 kilograms of germanium. Running these 5 towers of detectors for 9 months should improve our sensitivity by another order of magnitude. (0:15) 9/15/05 Penn State Colloquium

Sensitivity Expectations: Distant Future 9/15/05 Penn State Colloquium

Projected Sensitivies 9/15/05 Penn State Colloquium

CDMS Collaboration(March 2002) 9/15/05 Penn State Colloquium

DAMA – 100 kg of NaI Iodine, A=127 Eobs(KeVee)0.09 Erecoil (KeV) Sodium, A=23 Eobs(KeVee)0.25 Erecoil (KeV) Erecoil  Light NaI PMT Copper Lead Poly 9/15/05 Penn State Colloquium

DAMA Background and Signal Energy Spectrum Bkgd  1 cpd/kg/keV 2-6 KeV 8-24 KeV Na(23) 20-70 KeV I(127) 0.01950.031 -0.00010.019 cpd/kg/keV through 2003 … 6.3  Bernabei et al., astro-ph/0307403 through 2000 … 4 9/15/05 Penn State Colloquium

Similar Exposure… Stanford Site Nuclear Recoils Surface electrons Z1 () or Z5 (+) Neutrons!! Soudan rock filters the muons that make them (but not WIMPS) 9/15/05 Penn State Colloquium

Limits DAMA 1-4 58,000 kg-days CDMS Stanford Edelweiss Non-blind blind (10’s of kg-days) Various Models 9/15/05 Penn State Colloquium