Carlos Hernandez Faham- The Large Underground Xenon (LUX) Dark Matter Experiment
Transcript of Carlos Hernandez Faham- The Large Underground Xenon (LUX) Dark Matter Experiment
Carlos Hernandez FahamBrown University
www.luxdarkmatter.org
BNL Forum, May 27 2010
The Large Underground Xenon (LUX)Dark Matter Experiment
The LUX Experiment, May 27 2010 Carlos Hernandez Faham, Brown University
If you only have 30 seconds...
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Large Underground Xenon
• Ultra-low background, 350 kg liquid xenon time-projection chamber
• Aims to directly detect the (potentially) rare interactions between WIMPs and us
• To be deployed underground at SUSEL (Homestake mine in SD) in 2011
• It’s big: in less than 2 days, it will surpass all current limits set today
LUX
The LUX Experiment, May 27 2010 Carlos Hernandez Faham, Brown University 3
Richard Gaitskell PI, Professor
Simon Fiorucci Postdoc
Monica Pangilinan Postdoc
Luiz de Viveiros Graduate Student
Jeremy Chapman Graduate Student
Carlos Hernandez Faham Graduate Student
David Malling Graduate Student
James Verbus Graduate Student
Brown XENON10, CDMS
Thomas Shutt PI, Professor
Dan Akerib Professor
Mike Dragowsky Research Associate Professor
Carmen Carmona Postdoc
Ken Clark Postdoc
Karen Gibson Postdoc
Adam Bradley Graduate Student
Patrick Phelps Graduate Student
Chang Lee Graduate Student
Case Western SNO, Borexino, XENON10, CDMS
Bob Jacobsen ProfessorKevin Lesko Senior PhysicistYuen-Dat Chan ScientistBrian Fujikawa ScientistMia Ihm Graduate Student
Lawrence Berkeley SNO, KamLAND
Masahiro Morii ProfessorMichal Wlasenko Postdoc
Harvard BABAR, ATLAS
Adam Bernstein PI, Leader of Adv. Detectors Group
Dennis Carr Senior Engineer
Kareem Kazkaz Staff Physicist
Peter Sorensen Postdoc
Lawrence Livermore XENON10
University of MarylandEXO
Xinhua Bai ProfessorMark Hanardt Graduate Student
Frank Wolfs ProfessorUdo Shroeder ProfessorWojtek Skutski Senior ScientistJan Toke Senior ScientistEryk Druszkiewicz Graduate Student
James White ProfessorRobert Webb ProfessorRachel Mannino Graduate StudentTyana Stiegler Graduate StudentClement Sofka Graduate Student
Mani Tripathi Professor
Robert Svoboda Professor
Richard Lander Professor
Britt Hollbrook Senior Engineer
John Thomson Engineer
Matthew Szydagis Postdoc
Jeremy Mock Graduate Student
Melinda Sweany Graduate Student
Nick Walsh Graduate Student
Michael Woods Graduate Student
SD School of Mines
Texas A&M
UC Davis Double Chooz, CMS
ZEPLIN II
Carter Hall ProfessorDouglas Leonard Postdoc
Daniel McKinsey Professor
James Nikkel Research Scientist
Sidney Cahn Research Scientist
Alexey Lyashenko Postdoc
Ethan Bernard Postdoc
Louis Kastens Graduate Student
Nicole Larsen Graduate Student
DongMing Mei ProfessorWengchang Xiang PostdocChao Zhang PostdocJason Spaans Graduate StudentXiaoyi Yang Graduate Student
University of Rochester
U. South Dakota
Yale
ZEPLIN II
Majorana, CLEAN-DEAP
XENON10, CLEAN-DEAP
IceCube
Formed in 2007, fully funded DOE/NSF in 2008
The LUX Collaboration
The MotivationWIMPs?
The LUX Experiment, May 27 2010 Carlos Hernandez Faham, Brown University
Dark Matter
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70%
25%
5%
Dark Energy
Dark Matter
Us
Supernovae Ia
CMB
G. Lensing
BBN
Dark Matter as Weakly Interacting Massive Particles (WIMPs)• Cross-sections of order of weak scale give good estimate of current relic density• Independently, SUSY predicts a massive, weakly interacting particle
RotationCurves
The LUX Experiment, May 27 2010 Carlos Hernandez Faham, Brown University
Dark Matter: Direct Detection
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χ
χ
χ
ρχ 0.3 GeV
cm3
dNdER
∝e−ER /(E0r )
E0r⎛⎝⎜
⎞⎠⎟⋅ F2 (ER ) ⋅ I( )
I ∝ A2 (for S.I. interactions)
Local Milky Way DM density
Assume Maxwell-Boltzman DM velocity distribution
Low-energy threshold is vitalL. De Viveiros
Found it!
High-energy physicists:
TeV is far, far away
The PlanThe LUX Detection Mechanism
The LUX Experiment, May 27 2010 Carlos Hernandez Faham, Brown University
Xenon Signal
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Electron Recoil
Nuclear Recoil
e-e-e-e-e-
e-e-
e-e-
e-
e-
e-e-e- e-
175 nm photons Electrons
S1 S2Two signals:
Electron Recoil
Nuclear Recoil
The LUX Experiment, May 27 2010 Carlos Hernandez Faham, Brown University 9
ELiquid Xe
Gas Xe
PhotomultiplierTube
Anode Grid
Cathode Grid
The LUX Experiment, May 27 2010 Carlos Hernandez Faham, Brown University 10
e-e-e-e-e-
e- e-e-e-
S1
The LUX Experiment, May 27 2010 Carlos Hernandez Faham, Brown University 11
Δt Δt
top hit pattern:x-y localization
: z localizationx
S2e-e-e-e-e-
e- e-e-e-
The LUX Experiment, May 27 2010 Carlos Hernandez Faham, Brown University
The LUX Experiment
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Thermosyphon
2’’ Hamamatsu R8778Photomultiplier Tubes (PMTs)
Titanium Vessels
PMT Holder Copper Plates
• 350 kg LXe detector• 122 PMTs (2’’ round)• Low-background Ti cryostat• PTFE reflector cage• Thermosyphon used for cooling (>1 kW)
Dodecagonal field cage+ PTFE reflector panels
The ChallengeBackgrounds
The LUX Experiment, May 27 2010 Carlos Hernandez Faham, Brown University
The Challenge: Backgrounds
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• Ambient radioactivity:• ~100 evts/kg/s
• Human gamma activity:• ~10,000 gammas/s• Ellis: “What happens if I put a cat in the detector?” - Just don’t do it
• Walls (U/Th/K):• Concrete: 25/5.5/640 Bq/kg• Rhyolite rock: 100/45/900 Bq/kg
• U/Th/K radioactivity is everywhere!
• Muons at sea level: •1/hand/s (50 Hz with >300 MeV deposited in LUX at sea level)
WIMP
We’re looking for a few events/100kg/year!
(Just to give you an idea)
Wha
t WIM
P?
The TricksUnderground / Self-shielding / Discrimination / Water shield / Material Selection
The LUX Experiment, May 27 2010 Carlos Hernandez Faham, Brown University
The Tricks: Underground Operation
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LUX
~1 / hand / s
~1 / hand / months
Shhh... it’s quiet underground
The LUX Experiment, May 27 2010 Carlos Hernandez Faham, Brown University
The Tricks: Xenon Self-shielding
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• LXe is a dense target at 3 g/cc• Self-shielding allows this technology to greatly benefit from scaling up
10 kg
300 kg
LUX Goal
It’s quiet in the middle
The LUX Experiment, May 27 2010 Carlos Hernandez Faham, Brown University
The Tricks: Discrimination
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The LUX Experiment, May 27 2010 Carlos Hernandez Faham, Brown University
The Tricks: Water Shield
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Water shield: • 8m by 6m tank with 300 tonnes of water• Reduces gamma background by 10-10
• Reduces high-energy (>10 MeV) neutrons by 10-3
• Water tank is active (Cerenkov), with 20 8-inch veto PMTs, which further reduces external backgrounds
External bg
Internal bg
The LUX Experiment, May 27 2010 Carlos Hernandez Faham, Brown University
The Tricks: Material Screening and Contaminant Reduction
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• PMTs• 10/2/65 mBq/PMT (U/Th/K) and 2 n/year/PMT• However, multiply by x122 and consider the fact that they are right next to the active region...• They are the dominant source of internal background• In 30,000 kg-days, in fiducial region and in 5-25 keVr , all PMTs would contribute:
• 0.5 gamma events• 0.1 neutron events
• Titanium Cryostat• Very low radioactivity: <0.4 mBq/kg U+Th• Largely subdominant
• Rn• Cleanroom reduces levels to < 40 Bq/m3.• Minimize exposure, increase airflow
• Kr• Present in commercial Xe at ppm level. Reduced to <2 ppt with charcoal column separation
Mor
e ra
dioa
ctiv
eLe
ss r
adio
activ
e
PMT
PTFE
The LUX Experiment, May 27 2010 Carlos Hernandez Faham, Brown University
The LUX Program
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2007-2009
LUX0.1 - CWRU
2010
LUX - Surface
2011+
LUX - Underground
The LUX Experiment, May 27 2010 Carlos Hernandez Faham, Brown University
Past: LUX0.1 at Case Western
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• Surface run at Case Western Reserve University during 2007-2009 • Full assembly of LUX subsystems:
‣ Cryogenics‣ Recirculation‣ Slow control & safety systems‣ Electronics chain‣ PMT mounts and resistor-chain bases‣ Analysis software
• 50 kg Xe total mass (260 kg Aluminum filler displacer)• 4 PMT operation, 5 cm active Xe region
• Very encouraging milestones: • Achieved electron drift length > 2 m (purification rate with 9 hr e-folding)• Gamma and neutron calibrations
The LUX Experiment, May 27 2010 Carlos Hernandez Faham, Brown University
Present: LUX at the Sanford Surface Facility
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The dress rehearsal • Full-scale LUX assembly and deployment
• Duplicate of the underground layout• Smaller water tank (3 m)• Cleanroom class 1,000 (will be relocated underground)
• LUX operations since November 2009
The LUX Experiment, May 27 2010 Carlos Hernandez Faham, Brown University
Very near future: LUX Underground (Davis Cavern)
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Two story, dedicated LUX 55’ x 30’ x 32’ facility
0.2 km
LUXMajorana
4850 ft level
The LUX Experiment, May 27 2010 Carlos Hernandez Faham, Brown University
Projected Sensitivity
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WIMP Mass [GeV/c2]
Cro
ssse
ctio
n [c
m2 ] (
norm
alis
ed to
nuc
leon
)
100504200101
http://dmtools.brown.edu/ Gaitskell,Mandic,Filippini
101 102 10310 46
10 45
10 44
10 43
10 42
LUX (30,000 kg-days)
XENON100 (6,000 kg-days)
SuperCDMS 2-ST
XENON100 (161 kg-days)
CDMS 2009
Thank you
Extra Slides
The LUX Experiment, May 27 2010 Carlos Hernandez Faham, Brown University
LUX Dark Matter Signal
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0 5 10 15 201
1.5
2
2.5
3
3.5Simulated WIMP Signal ( mWIMP = 100 GeV/c2; WN = 2.1e 45 cm2 ; 3e4 kg day
S1 [keVee] (2.2 phe/keVee)
log1
0 ( S
2/S1
)
2009 Apr 14 01:06:21
)
L. De Viveiros
The LUX Experiment, May 27 2010 Carlos Hernandez Faham, Brown University
Why WIMPs?
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Γ = nχ < σ Av >= H
Ωχ ≈(0.1pb)ch2 < σ Av >
Ωχ ≈ 0.2For < σ Av >~ 1pb ⋅ c
The LUX Experiment, May 27 2010 Carlos Hernandez Faham, Brown University
Xenon Signal Generation
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The LUX Experiment, May 27 2010 Carlos Hernandez Faham, Brown University
LUX0.1 at Case Western: Pulses
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0 5 10 15 200
50
100
150LUX 0.1 Event (Summed across all channels)
J. Chapman 01 Oct 2009 Brown Particle Astrophysics
µs
phe/
sam
ple
0.5 0 0.50
5
10S1
µs
phe/
sam
ple
17 18 190
20
40
60
S2
µs
52.8 phe
4543 phe
S1
S2
The LUX Experiment, May 27 2010 Carlos Hernandez Faham, Brown University
LUX0.1 at Case Western: LXe Purity
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0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 5.51.5
2
2.5
3
3.5
4
4.5
5
Electron Drift Length [cm]
log10
(S2)
[phe
]Comparison of Electron Drift Lengths for Different Xe Purity Levels
e!folding drift length:0.181±0.001 cme!folding drift length:12.4±0.9 cm
0 5 10 15
0
2
4
6
8
10
phe/µ
s
Time [µs]
S1 Pulse
S2 Pulse
Electron Drift Time
The LUX Experiment, May 27 2010 Carlos Hernandez Faham, Brown University
LUX0.1 at Case Western: LXe Purity
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0 20 40 60 80 100 120
10
10
100
Recirculation Time [hours]
Elec
tron
Drif
t Len
gth
[m]
Purification vs. Time, Run009
2 error bars1 error bars
• ~9 hr purification time constant at 20 slpm (LUX will run at 50 slpm)
• > 2 m electron drift length
• This is an order of magnitude faster recirculation than ever achieved before
The LUX Experiment, May 27 2010 Carlos Hernandez Faham, Brown University
LUX0.1 at Case Western: Energy Calibrations
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