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DARK MATTER SEARCH

DARK MATTER SEARCH. Carter Hall, University of Maryland. Direct detection of WIMP dark matter. ~ 3 00 proton masses per liter of space. If M WIMP ~ 100 GeV, then 3 WIMP/liter. Typical orbital velocity ~ 230 km/sec, or 0.1% speed of light. Coherent scaler interactions: ~ A 2.

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DARK MATTER SEARCH

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  1. DARK MATTER SEARCH Carter Hall, University of Maryland

  2. Direct detection of WIMP dark matter • ~ 300 proton masses per liter of space. If MWIMP ~ 100 GeV, then 3 WIMP/liter. Typical orbital velocity ~ 230 km/sec, or 0.1% speed of light. Coherent scaler interactions: • ~ A2 Rate < 1 event / kg / 100 days, or much, much lower

  3. It’s not difficult to shield at 10 keV Gamma interaction cross section typical WIMP recoil energies Only MeV g’s can penetrate, but only keV g’s can fake a WIMP

  4. Self-shielding of liquid xenon is extremely powerful Fiducial volume cut rejects most backgrounds

  5. Self-shielding effect Sensitivity improves quickly as target mass increases! must cross full volume without scattering again ~keV scattering event – forward scattering ~MeV g

  6. Particle ID: nuclear recoil discrimination Ionization-to-scintillation ratio allows discrimination between common radioactivity and WIMP events. Background rejection factor of ~180

  7. The Hunters Hut Homestake (SD)

  8. Homestake Solar Neutrino Experiment 2002

  9. Davis Cavern @ Homestake, September 2009

  10. Davis Cavern @ Homestake, March 2011

  11. LUX Detector - Overview LN bath column Feed-throughs for cables / pipes Radiation shield Titanium Vessels Anode grid 59 cm Dodecagonal field cage+ PTFE reflector panels PMT holding copper plates 49 cm Cathode grid Counterweight Gaitskell - Brown University / LUX

  12. LUX – Surface Facility @ Homestake

  13. LUX 350 kg detector under assembly

  14. LUX 350 kg detector under assembly

  15. Test deployment of LUX in the Surface Facility Water Tank – April 2010

  16. Test deployment of LUX in the Surface Facility Water Tank – April 2010 Cryostat successfully cooled to liquid xenon temperature – May 2010

  17. 1.5 ppt Kr open leak valve New analytic technique to detect krypton at the part-per-trillion level arXiv:1103.2714v1

  18. Detect electronegative impurities at less than a part-per-billion arXiv:1002.2742 Xe is constant due to cold trap ~few ppm Ar 18 ppb N2 5 ppb O2 0.25 ppb CH4 open leak valve, bypass gas purifier flow through gas purifier bypass gas purifier close leak valve to measure backgrounds

  19. Experiment to test removal of tritiated methane Xe proportional tube for tritium counting Xe purifier CH3T storage bottle FE-55 x-ray calibration • > 99.9% of CH3T removed in one pass • Liquid Xenon removal test in this summer

  20. Thermosyphon cooling system

  21. Xenon Purity measured in a 60 kg test run 0.2 tonnes circulation per day • ~9 hr time constant for purification • > 2 m electron drift length achieved(> 1000 us) with 60kg target • Errors dominated by use of 5 cm test cell drift within large cryostat

  22. Heat Exchanger Operates >96% Efficient Demonstrated - 18 W required to circulate 0.4 tonnes of Xe a dayEvaporate Liquid > Gas / Purification -> Re-condense Liquid

  23. LUX dark matter sensitivity Status: LUX is being now being tested on the surface at Homestake. Move underground in December 2011.

  24. The LUX Collaboration Collaboration meeting, Homestake, March 2010 Brown XENON10, CDMS Case Western SNO, Borexino, XENON10, CDMS Formed in 2007, fully funded DOE/NSF in 2008 University of Rochester SD School of Mines Harvard IceCube ZEPLIN II BABAR, ATLAS Texas A&M Lawrence Berkeley + UC Berkeley ZEPLIN II SNO, KamLAND U. South Dakota Majorana, CLEAN-DEAP UC Davis Double Chooz, CMS Lawrence Livermore XENON10 Yale XENON10, CLEAN-DEAP University of Maryland EXO

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