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?


Dark Matter

5

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


Dark Matter: Direct Detection

6

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


Xenon Signal

8

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


ELiquid Xe

Gas Xe

PhotomultiplierTube

Anode Grid

Cathode Grid


e-e-e-e-e-

e- e-e-e-

S1


Δt Δt

top hit pattern:x-y localization

: z localizationx

S2e-e-e-e-e-

e- e-e-e-


The LUX Experiment

12

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 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 Tricks: Underground Operation

16

LUX

~1 / hand / s

~1 / hand / months

Shhh... it’s quiet underground


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 Tricks: Discrimination

18


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 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 Program

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2007-2009

LUX0.1 - CWRU

2010

LUX - Surface

2011+

LUX - Underground


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


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


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


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


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


Why WIMPs?

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Γ = nχ < σ Av >= H

Ωχ ≈(0.1pb)ch2 < σ Av >

Ωχ ≈ 0.2For < σ Av >~ 1pb ⋅ c


Xenon Signal Generation

30


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


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


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


LUX0.1 at Case Western: Energy Calibrations

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carlos hernandez faham- the large underground xenon (lux) dark matter experiment

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