Direct Detection of Dark Matter CDMS and COUPP

Direct Detection of Dark Matter: CDMS and COUPP Andrew Sonnenschein September 26, 2007 CDMS and COUPP

CDMS Collaboration at Soudan DOE Laboratory Fermilab LBNL DOE University Brown Cal. Tech 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 2

CDMS-II Detectors Phonon signal From a quadrant Phonon signal from one quadrant A D B C Charge signal Direct detection of WIMP signal Nuclei recoil by elastic scattering Read both phonon signal (4 channels) and ionization signal (inner and outer electrode) From inner electrode 1 cm thick, 7. 8 cm diameter 250 g Germanium, 100 g Silicon September 26, 2007 CDMS and COUPP 3

CDMS Subsystems x 5 Detectors Ge and Si crystals, 6/tower Measure ionization and phonons Cryogenics Maintain detectors at 50 m. K Electronics/ DAQ Record signals from detectors and veto; form trigger 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 4

CDMS II Ongoing Run 814 kg-day exposure DAMA Large calibration data sets MSSM mit S li M D d. C e h s li Pub limit 0 y on 1 n e tivit i X s n se cted e p Ex High efficiency for collecting data September 26, 2007 CDMS and COUPP 5

Super. CDMS 25 kg • Proposed 25 -kg experiment based on updated 42 x 600 -g Ge ZIPs – – 120 x beyond current limits 15 x beyond CDMS-II goal Approved for space at SNOLAB Next step towards ton-scale goal • Detector fabrication and characterization underway – Detectors have 3 x fiducial volume of CDMS-II design. – Cost per kg reduced to ~1/3. September 26, 2007 CDMS and COUPP 6

Fermilab responsibilities Established roles in CDMS New roles for Super. CDMS Backgrounds 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 September 26, 2007 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 Si. Det 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 CDMS and COUPP 7

Super. CDMS 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 8

Progress on Super. CDMS New warm electronics prototype for Super. CDMS Replaces a chain of four 9 U-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 9

Super. CDMS Sensitivity DAMA 5 4+200 0 0 2 dan S Sou M D 07 C PS 20 dan Proj A 0 1 N Sou XENO CDMS Proj g k 0 0 3 LUX Proj b a L O N DMS S Super. C KIMS ST CRES WEISS EDELLIN II ZEPRP WA 1 ev/kg/month 1 ev/kg/year 1 ev/10 kg/year 1 ev/ton/year September 26, 2007 CDMS and COUPP 10

Dark Matter in Bubble Chambers WIMP Nuclear recoil E ~ 1 -100 ke. V heavy target nucleus e. g. 127 I 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 September 26, 2007 CDMS and COUPP

COUPP: Dark Matter Detection with Bubble Chambers Muon September 26, 2007 CDMS and COUPP WIMP?

The COUPP Team Principal Investigator: Juan Collar (spokesperson) Wilson Fellows: Andrew Sonnenschein Principal Investigator: Ilan Levine Graduate Students: Nathan Riley Matthew Szydagis Staff Scientists: Peter Cooper Mike Crisler Martin Hu Erik Ramberg Bob Tschirhart Undergraduates: Earl Neeley Tina Marie Shepherd Undergraduates: Luke Goetzke Hannes Schimmelpfennig KICP Fellows: Brian Odom University of Chicago Engineers: Ed Behnke Fermi National Accelerator Indiana University Laboratory South Bend Funding National Science Foundation Kavli Institute for Cosmological Physics September 26, 2007 Department of Energy CDMS and COUPP 13

1 -Liter Chamber in Nu. Mi Tunnel Design concept: September 26, 2007 CDMS and COUPP

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 September 26, 2007 CDMS and COUPP

Spatial Distribution of Bubbles Two populations: – Walls: apparently from radium contamination of quartz. – Bulk: radon dissolved in chamber liquid September 26, 2007 CDMS and COUPP

Data from 2006 Run • First physics results were shown at Fermilab last week. • Data from pressure scan at two temperatures: Energy Threshold In Ke. V Radon background Solid lines: Expected WIMP response for September 26, 2007 CDMS and COUPP SD(p)=3 pb 17

Results from 2006 Run • We have competitive sensitivity for spin-dependent scattering, despite high radon background Spin-dependent September 26, 2007 Spin-independent CDMS and COUPP 18

New Low-Background Vessel • Teflon-coated inconel seals replace Viton. Radon emanation <1% of previous design Water • Quartz etched with HF acid by vendor to remove implanted radon daughters. • All parts cleaned and assembled in Accelerator Division RF cavity cleaning facility. CF 3 I September 26, 2007 • Very high purity, well-studied water from Sudbury Neutrino Observatory. • Bellows made using non-thoriated welding electrodes. CDMS and COUPP

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. September 26, 2007 CDMS and COUPP

COUPP 60 Kg Chamber • Construction of 60 kg chamber approved by the PAC and director in Fall, 2006. Now being built. September 26, 2007 CDMS and COUPP