CLEAN: A Detector for Dark Matter and Low-Energy Solar n

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CLEAN A Detector for Dark Matter and Low-Energy
Solar ns

• Liquid neon as a target for dark
• matter and neutrino interactions
• (the CLEAN experiment)
• Position reconstruction/backgrounds
• in CLEAN
• Experimental sensitivity
• Dependence on optical and detector
• properties
• Test Bench at Yale (pico-CLEAN)

• Idea for Dark Matter with LAr

Mark Boulay
arxiv.org/astro-ph/0402007
arxiv.org/nucl-ex/0410025
Favorable review from SNOLab EAC
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GEANT4 MC of scintillation events in CLEAN

• 15000 photons/MeV
• 60 cm Rayleigh scattering at 80 nm
• 75 coverage, 1842 PMTs 15 QE
• 80 nm shifted to blue for detection

CLEAN RD Collaboration Boston University Ed
Kearns Los Alamos National Laboratory Mark
Boulay, Andrew Hime, Jeff Lidgard, Dongming
Mei NIST Kevin Coakley Yale University Hugh
Lippincott, Matthew Harrison, Benjamin Jorns, Dan
McKinsey, James Nikkel
250 keV electron at z250 cm
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Scintillation in liquid neon
Ionizing radiation leads to formation of dimers
in Neon Singlet and triplet states are produced,
decay times are 3 ns (singlet, prompt) and 2.9
ms (triplet, late) Amount of prompt and late
components depends on particle Electron recoils
promptlate 13 Nuclear recoils mostly
prompt (being measured at Yale) Allows
discrimination between electron recoils
(neutrinos, betagamma) from nuclear recoils
(WIMPs, neutrons)
This discrimination can be achieved with a simple
detector design (no need for electron drift),
possible advantage
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Backgrounds, backgrounds, backgrounds

• The CLEAN approach
• With material selection, clean target,
• sufficient depth, and appropriate cuts,
• provide a signal region which will contain
• only signal events (solar nus and WIMPs)
• (basically the SNO approach)
• Internal radioactivity-gtclean materials
• External radioactivity-gtreconstruction cuts
• Neutrino vs WIMP separation-gttiming PSD
• interesting aside SNO NC detection corresponds
  to 10-6 events/kg/day

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Time-of-flight (TOF) information for vertex
reconstruction
Tres Tpmt Tfit dpmt/vphoton
2d pdf in Tres, Revent
Scattering introduces position dependence to
Tres, and broadens the distribution, but this
info is still useful
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Likelihood surface using TOF information
Likelihood surface (in detector x,y coordinates)
for event at x 294 cm, near PMT Deep minimum
near event location In likelihood surface can be
used to precisely locate event,
improve Background rejection
X2 improvement in position resolution with TOF
information! -gtPMT data can be used for PMT
background rejection and WIMP/e discrimination
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Expected physics signals in CLEAN
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External backgrounds after fiducial cut
Commercially available ultra-low background
PMT Glass 30 ppb U, Th 60 ppm K
sample 300 cm detector with 125 cm fiducial cut
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Distinguishing WIMPs from electrons
PMT TOF spectra
Time distribution of PMT hits Are different for
electron recoils (neutrinos) and nuclear
recoils (WIMPs)
Ratio of prompt/late hits can separate
(statistically) electron and nuclear
recoils -gtFrom simulation, limit on WIMP events
is 1 events/year in solar neutrino background
for 125 cm volume of Neon
prompt ratios

• Expect improvement

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Sensitivity to WIMPs and neutrinos with liquid
neon
WIMP sensitivity
pp statistical uncertainty
10-46
lt1
300 cm
1 year livetime
Detector size
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Sensitivity to PMT backgrounds
/- factor of 10 on PMT activity
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Dependence on optical parameters
Scintillation time
Quenching factor
Rayleigh scattering
Scintillation yield
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(No Transcript)
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DD neutron generator at Yale
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pico-CLEAN at Yale for scintillation measurements
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Noble Gas Purification System at LANL
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Summary of potential advantages of Liquid Neon

• In principle can be CLEANed to levels needed for
• simultaneous Dark Matter/pp neutrino experiment
• Spherical target volume can be scaled to large
  target
• masses needed for next-generation sensitivity
• Spherical (SNO-like) design allows for
  fiducialization
• and hence mitigation of external source
  backgrounds
• Intrinsic pulse shape discrimination (e- vs
  nuclear recoils)
• allows for a simple, single-detector-system
  design
• pp neutrino sensitivity should lead to a positive
  result
• Can be complementary to WIMP search with heavier
  target

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http//arxiv.org/astro-ph/0411358
scintillation pulse-shape analysis for
discrimination of e- vs nuclear recoils -gt no
electron-drift
DEAP Dark-matter Experiment with Argon PSD
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DM with liquid argon PSD (DEAP)

• 6 pe/keV for 75 coverage, with
• 1500 Hz PMT noise
• Backgrounds from Ham. R9288 (approx. 70 mBq/PMT)
• 5 ns PMT resolution
• 20 photon detection efficiency
• 100 ns trigger window sets T0
• Fprompt Prompt hits(100 ns)/Total hits(15 us)
• 2 kg Ar with 10 keVee threshold (60 pe)

Dominant backgrounds assuming proper shielding,
depth, and clean construction.
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Effect of Form Factor Suppression
Integrated rates above threshold with 25
quenching
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Background rejection with LAr (simulation)
From simulation, rejection gt 108 _at_ 10
keV (Goal for SuperCDMS is 108 from R.
Schnee talk on Thurs.)
108 simulated e-s
100 simulated WIMPs
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DM Sensitivity with LAr, LNe with 1-year exposure
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DEAP at LANL

• LAr cryostat under construction at LANL
• Test PMTs in LAr for timing, efficiency,
  stability,
• noise rate, pulse shape (ionic afterpulsing)
• Build small 4p detector with pulse digitization
• to demonstrate PSD
• Construct shielding and move U/G to WIPP
• or SNOLab for WIMP search
• Design larger-scale (100 kg) experiment

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Conclusions
PSD in LAr, LNe looks promising due to long
triplet time (microsec) A Liquid neon experiment
may be a relatively simple DM experiment with
good sensitivity, and has sensitivity to solar
neutrinos (positive physics result even if no
WIMP signal is seen). -gt Form factors and effect
of energy thresholds, competes with large-A
coherence, so that neon is within X6 of
xenon, and argon is comparable to xenon for
reasonable thresholds pico-CLEAN in progress at
Yale for Ne scintillation parameters needed to
evaluate DM capability
Potential for PSD in liquid argon dedicated-DM
experiment -in progress at LANL (DEAP)