Direct Detection of Dark Matter: CDMS and COUPP Test Direct Detection of Dark Matter: CDMS and COUPP Andrew Sonnenschein

CDMS Collaboration at Soudan Test CDMS Collaboration at Soudan DOE Laboratory Fermilab LBNL DOE University Brown CalTech Florida Minnesota MIT Stanford UC Santa Barbara NSF Case Western Reserve Colorado (Denver) Santa Clara UC Berkeley Canada Queens September 26, 2007 CDMS and COUPP

CDMS-II Detectors Direct detection of WIMP signal Test CDMS-II Detectors Phonon signal From a quadrant Phonon signal from one quadrant D C A B Charge signal From inner electrode Direct detection of WIMP signal Nuclei recoil by elastic scattering Read both phonon signal (4 channels) and ionization signal (inner and outer electrode) 1cm thick, 7.8 cm diameter 250g Germanium, 100g Silicon September 26, 2007 CDMS and COUPP

CDMS Subsystems Detectors Ge and Si crystals, 6/tower Test CDMS Subsystems Detectors Ge and Si crystals, 6/tower Measure ionization and phonons Electronics/DAQ Record signals from detectors and veto; form trigger x5 Cryogenics Maintain detectors at 50 mK Shielding Layered shielding (Cu, Pb, polyethylene) reduces radioactive backgrounds and active scintillator veto is >99.9% efficient against cosmic rays. September 26, 2007 CDMS and COUPP

CDMS II Ongoing Run 814 kg-day exposure September 26, 2007 Test CDMS II Ongoing Run Expected sensitivity Xenon10 limit Published CDMS limit DAMA MSSM 814 kg-day exposure Large calibration data sets High efficiency for collecting data September 26, 2007 CDMS and COUPP

Test SuperCDMS 25 kg Proposed 25-kg experiment based on updated 42 x 600-g Ge ZIPs 120x beyond current limits 15x beyond CDMS-II goal Approved for space at SNOLAB Next step towards ton-scale goal Detector fabrication and characterization underway Detectors have 3x fiducial volume of CDMS-II design. Cost per kg reduced to ~1/3. 4x - rejection (H-si; phonon converage) 2x - analysis 5x - bkg reduction (thickness; as clean as cleanest) ->40x, but need only 20x September 26, 2007 CDMS and COUPP

Fermilab responsibilities Test Fermilab responsibilities Established roles in CDMS Project Management Operations Lead the Soudan operations Cryogenics Design, construction of the cryogenics systems Electronics, DAQ, Computing Warm electronics, event builder software, online and offline processing Infrastructure Clean rooms, control rooms, computing rooms Analysis Independent analysis chain New roles for SuperCDMS Backgrounds Collaborating with COUPP on understanding Radon, alpha screening Shield/Veto Do mechanical design and construction together with cryogenics Detectors Exploring possibilities for automated inspection and repair at SiDet May also get involved in bonding our sensors to larger crystals Systems Test Put everything together at Fermilab and test before taking to SNOLAB Need more scientist and engineering help to push forward these new areas September 26, 2007 CDMS and COUPP

SuperCDMS Cryogenics Design Test SuperCDMS Cryogenics Design Cryogen-free dilution refrigerator Much lower operations and maintenance cost Larger volume to accommodate more detectors More robust thermal connections than in CDMS II September 26, 2007 CDMS and COUPP

Test Progress on SuperCDMS New warm electronics prototype for SuperCDMS Replaces a chain of four 9U-sized boards used for CDMS II Fewer connections, lower power draw => more robust Pulse tube cryocooler under test in clean room in Lab 3 at Fermilab September 26, 2007 CDMS and COUPP

SuperCDMS Sensitivity Test SuperCDMS Sensitivity 1 ev/kg/month 1 ev/kg/year 1 ev/ton/year DAMA KIMS CRESST EDELWEISS ZEPLIN II WARP CDMS Soudan 2004+2005 XENON10 APS2007 CDMS Soudan Proj SuperCDMS SNOLab Proj LUX 300kg Proj 1 ev/10 kg/year September 26, 2007 CDMS and COUPP

Dark Matter in Bubble Chambers Test Dark Matter in Bubble Chambers Nuclear recoil E ~ 1-100 keV  heavy target nucleus e.g. 127I WIMP Recoil range < 1 micron in a liquid, so the signal is a single bubble rather than a track. Measure the rate at which single bubbles appear

COUPP: Dark Matter Detection with Bubble Chambers Test COUPP: Dark Matter Detection with Bubble Chambers Muon WIMP?

The COUPP Team Wilson Fellows: Andrew Sonnenschein Staff Scientists: Test The COUPP Team Principal Investigator: Juan Collar (spokesperson) Graduate Students: Nathan Riley Matthew Szydagis Undergraduates: Luke Goetzke Hannes Schimmelpfennig KICP Fellows: Brian Odom Wilson Fellows: Andrew Sonnenschein Staff Scientists: Peter Cooper Mike Crisler Martin Hu Erik Ramberg Bob Tschirhart Principal Investigator: Ilan Levine Undergraduates: Earl Neeley Tina Marie Shepherd Engineers: Ed Behnke Fermi National Accelerator Laboratory Indiana University South Bend Funding University of Chicago National Science Foundation Kavli Institute for Cosmological Physics Department of Energy September 26, 2007 CDMS and COUPP

1-Liter Chamber in NuMi Tunnel Test 1-Liter Chamber in NuMi Tunnel Design concept:

Test A Typical COUPP Event Appearance of a bubble causes the chamber to be triggered. Bubble positions are measured in three dimensions from stereo camera views

Spatial Distribution of Bubbles Test Spatial Distribution of Bubbles Two populations: Walls: apparently from radium contamination of quartz. Bulk: radon dissolved in chamber liquid

Data from 2006 Run SD(p)=3 pb Test Data from 2006 Run First physics results were shown at Fermilab last week. Data from pressure scan at two temperatures: Energy Threshold In KeV Radon background Solid lines: Expected WIMP response for  SD(p)=3 pb September 26, 2007 CDMS and COUPP

Test Results from 2006 Run We have competitive sensitivity for spin-dependent scattering, despite high radon background Spin-dependent Spin-independent September 26, 2007 CDMS and COUPP

New Low-Background Vessel Test New Low-Background Vessel Water CF3I Teflon-coated inconel seals replace Viton. Radon emanation <1% of previous design Quartz etched with HF acid by vendor to remove implanted radon daughters. All parts cleaned and assembled in Accelerator Division RF cavity cleaning facility. Very high purity, well-studied water from Sudbury Neutrino Observatory. Bellows made using non-thoriated welding electrodes.

New Run of 1-liter Chamber Test New Run of 1-liter Chamber Inner vessel has been entirely rebuilt with materials believed to have lower radioactivity. New run started July 30, 2007. Some radon introduced during filling, now decaying to equilibrium.

Test COUPP 60 Kg Chamber Construction of 60 kg chamber approved by the PAC and director in Fall, 2006. Now being built.