Evidence and Motivation Dual-phase Noble Liquid Detectors Initial Work
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Transcript of Evidence and Motivation Dual-phase Noble Liquid Detectors Initial Work
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Dark Matter Searches with Dual-Phase Noble Liquid Detectors
Imperial HEP 1st Year Talks 1
‒ Evidence and Motivation‒ Dual-phase Noble Liquid
Detectors‒ Initial Work
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2Evidence for Dark Matter
‒ Astronomical Evidence– Galaxy Cluster masses– Galaxy rotation curves– Gravitational lensing
‒ Cosmological Evidence– Cosmic Microwave
Background (CMB)
‒ Want to find direct evidence, measure local dark matter in the Galaxy
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3Properties of Dark Matter
23.0%
4.6%72.4%
Dark MatterBaryonic MatterDark Energy
‒ Main properties:– Interact “weakly” with ordinary matter– Electromagnetically neutral– Massive– Stable
‒ Candidates:‒ MACHOs
– Massive Compact Halo Objects
‒ WIMPs– Weakly Interacting
Massive Particles‒ Other Particles
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4Direct Detection
‒ Signal– Nuclear recoil from WIMP
collision– Gives ionisation, scintillation
and phonons.
‒ Background– Other nuclear recoils– Electron recoils
‒ Look for interaction in detector material
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5Two-Phase Noble Liquid Detectors
‒ Discriminate electron recoils– Different amounts of ionisation and
scintillation ‒ Other recoils look like signal
– Need to minimise radioactivity
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6LUX Experiment‒ Large Underground Xenon‒ 370 kg with 100-150 kg fiducial
mass (self-shielding)‒ Two arrays of 61 PMTs
‒ My involvement– Data analysis– Simulation– Operations support
PMTsLXe
Cryostats
HV Feedthrough
Recirculation and Heat Exchanger
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7LZ Experiment‒ LUX-ZEPLIN
– Combination of LUX and ZEPLIN collaborations‒ Builds on previous LUX and ZEPLIN technology ‒ Same site – use previous infrastructure
‒ Working on R & D– Use two-phase xenon chamber at Imperial
LZ LUX
120 cm 49 cm
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8Electroluminescence Studies‒ Design work for LZ
– ZEPLIN-III achieved a high signal discrimination– Was this due to the high field, or an effect of the
geometry?
ZEPLIN-III LUX Grid‒ Simulated scenarios
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9Method
‒ Count photons and
find variance
‒ Photon emissions
‒ Propagation
Liquid
Gas
Anode Grid
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10Results
‒ Total Variance = 5.72 %
‒ Total Variance = 2.49%– Variance for each PMT array
was similar to ZEPLIN-III– Two PMT arrays improved it
ZEPLIN-III LUX Grid
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11Conclusions‒ Electroluminescence studies:
– Anode grid does not spoil resolution– Two PMT arrays improves resolution
‒ LUX is filled – now turning on‒ LZ currently being designed
WIMP Mass [GeV/c2]
Cros
s-se
ctio
n [c
m2 ]
(nor
mal
ised
to n
ucle
on)
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12Backup Slides
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13Electroluminescence Studies‒ Garfield++
– Calculates electric fields– Magboltz for properties of the gas– Drifts electrons through the chamber
‒ Drift lines for wire grid
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14Results‒ ZEPLIN-III geometry‒ 30% reflectivity from copper anode
Variance at Production Variance after Propagation
Num
ber o
f Eve
nts
Photons Emitted Photons at Bottom Tally
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15Results‒ LUX geometry with wire grid‒ 25% reflectivity from the steel wires
Num
ber o
f Eve
nts
Variance at Production Variance after Propagation
Photons Emitted Total Photon Tally
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16Results‒ LUX geometry with wire mesh‒ 25% reflectivity from the steel wires
Num
ber o
f Eve
nts
Variance at Production Variance after Propagation
Photons Emitted Total Photon Tally