Current status of LUX Dark Matter Experiment

PANIC11, 7/24/2011 LUX Experiment A. Lyashenko

Current status of LUX Dark Matter Experiment

by A. Lyashenko

Yale UniversityOn behalf of LUX collaboration


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


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


WIMP direct detection: two phase Xe

WIMP

S2/S1Gamma>>S2/S1WIMP

Gamma

Drift time

Top PMT Array

Bottom PMT Array


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


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?


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)


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


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


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


Trickery: ER/NR Discrimination

WIMPregion

XENON10 data

Electron Recoils

Nuclear Recoils

Cut 2-3 keVee

High energies 99.5%

Low energies 99.9%


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)


LUX Program Timeline

LUX 0.1

LUX Surface Run LUX DM Search Run

2007 - 2009

2010 - 2011

NOW!!!

2012+


Sanford Lab Surface Facility


May 2011 first cooldown

Held Target Temperature 180K

Flexible Temperature Control


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)


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


• 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


Extra Slides


Xe signal generation


Why WIMPs?


NR scintillation efficiency

Eee

A. Manzur et al., arXiv:0909.1063v4 and references therein


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


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

Current status of LUX Dark Matter Experiment

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