DARK MATTER SEARCH
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Transcript of DARK MATTER SEARCH
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DARK MATTER DARK MATTER SEARCHSEARCH
Carter Hall, University of MarylandCarter Hall, University of Maryland
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Direct detection of WIMP dark matter
00 proton massesper 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
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It’s not difficult to shield at 10 keV
typical WIMP recoil energies
Gamma interaction cross section
Only MeV ’s can penetrate,but only keV ’s can
fake a WIMP
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Self-shielding of liquid xenon is extremely powerful
Fiducial volume cut rejects most backgrounds
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Sensitivity improves quickly as target mass increases!Self-shielding effect
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Particle ID: nuclear recoil discrimination
Ionization-to-scintillation ratio allows discrimination between common radioactivity and WIMP events.
Background rejection factor of ~180
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The Hunters HutThe Hunters Hut Homestake (SD)Homestake (SD)
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Davis Cavern @ Homestake, 9/21/09
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Gaitskell - Brown University / LUX
LUX Detector - Overview
Titanium Vessels
Dodecagonal field cage+ PTFE reflector panels
PMT holding copper plates
Counterweight
Feed-throughs for cables / pipesLN bath column
Radiation shield
49 cm
59 cm
Cathode grid
Anode grid
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LUX 350 kg detector under construction
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Test fit of detector inside the titanium cryostat
Assembly & commissioning in a new laboratory on the surface at Homestake
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Xenon Purity measured in a 60 kg test run
• ~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
0.2 tonnes circulation per day
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Heat Exchanger Operates >96% EfficientDemonstrated - 18 W required to circulate 0.4 tonnes of Xe a
dayEvaporate Liquid > Gas / Purification -> Re-condense Liquid
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LUX dark matter sensitivity
Status: LUX is being now being assembled on the surface at Homestake.Expect to move underground in December 2010.
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Collaboration meeting @ Homestake mine, March 1, 2009Collaboration meeting @ Homestake mine, March 1, 2009