current status of lux dark matter experiment
TRANSCRIPT
PANIC11, 7/24/2011 LUX Experiment A. Lyashenko
Current status of LUX Dark Matter Experiment
by A. Lyashenko
Yale UniversityOn behalf of LUX collaboration
PANIC11, 7/24/2011 LUX Experiment A. Lyashenko
LUX – Large Underground Xenon experiment
LUX Collaboration:Yale, CWRU, UC Santa Barbara,Brown, TAMU, UC Davis, Harvard,LLNL, LIPP Coimbra, Rochester, LBNL, Maryland, South Dakota SMT
PANIC11, 7/24/2011 LUX Experiment A. Lyashenko
WIMP Dark matter
ρχ=0.3±0.1GeV∙cm-3
~3 WIMPs in 1L
Local Milky Way DM density:
Xe
Low Energy Threshold is vital
0-80keVR Recoil Energy
Assuming ΩDM = Ωχ WIMP DM
WIMP: stable, non-barionic, non-relativistic, el. neutral
mχ=10 GeV-few TeV scatter preferably from nuclei
PANIC11, 7/24/2011 LUX Experiment A. Lyashenko
WIMP direct detection: two phase Xe
WIMP
S2/S1Gamma>>S2/S1WIMP
Gamma
Drift time
Top PMT Array
Bottom PMT Array
PANIC11, 7/24/2011 LUX Experiment A. Lyashenko
LUX Detector
Top PMT Array
Bottom PMT Array
• 350 kg LXe (100 kg fiducial)• Ed=2kV/cm, Eextr=5kV/cm, Esc=10kV/cm• 122 PMTs (QE~30% @ 175nm)• Low Radioactivity Materials• >1kW Cooling Power (Thermosyphons)
Titanium Cans
Field Cage andTeflon ReflectorPanels
Thermosyphon
2” Hamamatsu R8778 PMTs
Water Tank
Detector Stand
59cm
49cm
PANIC11, 7/24/2011 LUX Experiment A. Lyashenko
Challenge: Backgrounds
Goal: few events/100kg/year !!!
• Sea level total muon flux: 55.2 m-2∙sec-1 (threshold 300 MeV)
• Ambient radioactivity: ~100 evts/kg/sec
• Human gamma activity 40K: ~4000 gammas/sec
• Walls (U/Th/K): - concrete 25/5.5/640 Bq/kg- rhyolite rock 100/45/900 Bq/kg
• Internal radioactivity
WIMP
Where isWIMP?
PANIC11, 7/24/2011 LUX Experiment A. Lyashenko
Trickery: Going Deep
LUX
4850 feet (1478 m)underground
HomestakeMine
55.2 m-2∙sec-110-5 m-2∙sec-1
~107 fold muon flux suppression
Sanford Underground Research Facility (SURF)
PANIC11, 7/24/2011 LUX Experiment A. Lyashenko
Trickery: Water Shield
Gamma suppression: ~10-7
Neutron suppression (>10 MeV): ~10-3
Neutron suppression (<10 MeV): <10-9
d = 8 m
6 m
20 Tonnesinverted steel pyramid
• 300 Tonnes of Water• Cherenkov ‘Muon Veto’ 20 Ø10” PMTs
PANIC11, 7/24/2011 LUX Experiment A. Lyashenko
Trickery: Understanding internal backgrounds
PMTs: 10/2/65 mBq/PMT (U/Th/K) and 2 n/year/PMTDominant source of background!!!
Titanium cryostat: <0.4 mBq/kg U+Th (very low!)
Cu: 10 ppt U / 12 ppt Th / 18 ppb K [~1% of ER BG budget]
Radon: Cleanroom reduces levels to <40 Bq/m3, Radon Cowl
Kr: present in Xe at ppm level <2 ppt level with charcoal column
PTFE: U/Th/K < 0.004/<0.001/0.053 mBq/kg 6∙10-8
events/keVee/kg/day [~1% of ER BG budget]
X 122
PANIC11, 7/24/2011 LUX Experiment A. Lyashenko
Trickery: Xe self shielding
Expect <0.5 nuclear/electron-recoils in 100 days
PMT gammas
PMT neutrons
Fiducial volume
PMTs are dominant background source
We benefit a lot from scaling up
10 kg
300 kg
PANIC11, 7/24/2011 LUX Experiment A. Lyashenko
Trickery: ER/NR Discrimination
WIMPregion
XENON10 data
Electron Recoils
Nuclear Recoils
Cut 2-3 keVee
High energies 99.5%
Low energies 99.9%
PANIC11, 7/24/2011 LUX Experiment A. Lyashenko
83mKr (half-life 1.86 hours)
• alpha source• S1 LY and keVee, e- lifetime• Fills entire fiducial volume
LUX calibrationExternal Sources Internal Sources
133Ba, 137Cs, 22Na, 208Tl (collimated):S1 LY, ER energy bands, e- lifetime241Am/Be: NR band
S1
9.4 keV 32.1 keV
Tritium (half-life 12.3 yrs)• Injected as CH3T• Beta source, up to 18.6 keV• Removed by purification system• S2/S1 ER band• Fills entire fiducial volume
L. Kastens et al., Phys. Rev. C80: 045809,2009,A. Manalaysay et al., Rev. Sci. Instr. 81, 073303 (2010)
PANIC11, 7/24/2011 LUX Experiment A. Lyashenko
LUX Program Timeline
LUX 0.1
LUX Surface Run LUX DM Search Run
2007 - 2009
2010 - 2011
NOW!!!
2012+
PANIC11, 7/24/2011 LUX Experiment A. Lyashenko
Sanford Lab Surface Facility
PANIC11, 7/24/2011 LUX Experiment A. Lyashenko
May 2011 first cooldown
Held Target Temperature 180K
Flexible Temperature Control
PANIC11, 7/24/2011 LUX Experiment A. Lyashenko
Expectations
WIMP events
LUX 4000 kg-days (MC simulation)
LUX – strong emphasis on WIMP discovery
LUX ~2days
LUX ~60days
LUX ~300days
Targeting at 7∙10-46 cm2 (@ 100GeV)
PANIC11, 7/24/2011 LUX Experiment A. Lyashenko
Future Plans: LZS/LZD ProjectsLZ = joint collaboration of LUX and ZEPLIN
LZS (Sanford) =1500 kg (1200 kg fiducial)
• LUX infrastructure designed to accommodate LZ
• Liquid scintillator veto
• Construction 2012–2013, operation 2014-2015
• σχ = 2x10-47 cm2 in 2 years
LZD = 20 ton concept
• 2 m diameter x 2 m height
• Will be in a deeper site, possibly 8000 feet
• Construction 2014–2016, operation 2017–2020
• σχ = 10-48 cm2 in 3 years
LUX
LZD
PANIC11, 7/24/2011 LUX Experiment A. Lyashenko
• Dark Matter puzzle convergence of astronomy and particle physics– Evidences point to WIMPs waiting to be discovered
• LUX experiment uses proven liquid Xe technology to reach σχ = 7x10-46 cm2
– Surface operation is in progress
– Dark Matter search run will start in 2012
– Just when the LHC will be searching for New Physics
• LZS/LZD will push the sensitivity to 10-48 cm2 by 2020
• We may know what Dark Matter is within this decade!!!
Summary
PANIC11, 7/24/2011 LUX Experiment A. Lyashenko
Extra Slides
PANIC11, 7/24/2011 LUX Experiment A. Lyashenko
Xe signal generation
PANIC11, 7/24/2011 LUX Experiment A. Lyashenko
Why WIMPs?
PANIC11, 7/24/2011 LUX Experiment A. Lyashenko
NR scintillation efficiency
Eee
A. Manzur et al., arXiv:0909.1063v4 and references therein
PANIC11, 7/24/2011 LUX Experiment A. Lyashenko
Tritiated methane (CH3T) removal experiment –Gaseous proportional tube counter
Xe proportional tubefor CH3T counting Xe purifier
• > 99.9% of CH3T removed from proportional tube in one pass through the purifier.• Liquid xenon removal test @ UMD this spring.
CH3T storage bottle
FE-55 x-raycalibration
Univ. of Maryland
PANIC11, 7/24/2011 LUX Experiment A. Lyashenko15
Case Western Reserve University
PANIC11, 7/24/2011 LUX Experiment A. Lyashenko
1.5 ppt Kr
open leak valve
New analytic technique to detect krypton at the part-per-trillion level
arXiv:1103.2714v1
GOAL: O(10) ppt 85Kr- Leads to an event rate of O(0.1) events in the 2-10 keVee regime after 104 kg-days and 99.5% rejection of e-
recoils
16
Residual Gas Analyzermass spectrometer
LN2