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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!

  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. Davis Cavern @ Homestake, 9/21/09

  9. 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

  10. LUX 350 kg detector under construction

  11. Test fit of detector inside the titanium cryostat Assembly & commissioning in a new laboratory on the surface at Homestake

  12. 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

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

  14. LUX dark matter sensitivity Status: LUX is being now being assembled on the surface at Homestake. Expect to move underground in December 2010.

  15. Collaboration meeting @ Homestake mine, March 1, 2009

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