Underground Searches for SUSY Dark Matter:XENON10 and Beyond

Kaixuan Ni*(XENON Collaboration)

Inaugural Conference of Institute for Gravitation and the CosmosPenn State University, Aug.9-11, 2007

* Supported by Yale University Postdoctoral Fellowship

the Dark Universe

2

beyond the Standard Model

3

✦ WIMPs (Weakly Interacting Massive Particles) as dark matter

➡ stable (formed in the big bang, freeze-out)➡ neutral (no EM interaction, only gravitational effects observed)➡ heavy (mass ~ 100 GeV to 1 TeV)

✦ a natural DM candidate from Supersymmetry: neutralino

➡ lowest mass superposition of photino, zino, higgsino➡ typical mass ~ 40 GeV to 1 TeV➡ stable (by R-parity conservation)

4

Direct Dark Matter Detection

Galactic WIMP Halo

(ρ = 0.3 GeV/cm3)

ElasticScattering

TargetNucleus

= 220 km/sRecoil Nucleus~10 - 100 keV

χχ

σW-p can be as low as 10-46 cm2

➡ neutralino can be directly detected on terrestrial target

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technical challenges

✦ Signal

➡ large mass

➡ low energy threshold

✦ background suppression

➡ deep underground

➡ passive shield

➡ low intrinsic radioactivity

➡ gamma background discrimination

6

R ≈ MdetMN

ρσ < v >

!"#$%!&''()%*+,-.-&-(/%#&0&,-%1223 45(+6%#7).5(

".8&.9%:(+;+%%?6--()%=(-(@-.;+

! "6)0(%#%AB%CDCE%0;;9%

technical challenges

✦ Signal

➡ large mass

➡ low energy threshold

✦ background suppression

➡ deep underground

➡ passive shield

➡ low intrinsic radioactivity

➡ gamma background discrimination

6

R ≈ MdetMN

ρσ < v >

!"#$%!&''()%*+,-.-&-(/%#&0&,-%1223 45(+6%#7).5(

".8&.9%:(+;+%%?6--()%=(-(@-.;+

! "6)0(%#%AB%CDCE%0;;9%

Two-phase Xenon Detector with 3-D Sensitivity

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WIMP or Neutronnuclear

recoil

electronrecoil

Gamma or Electron

Top PMT Array

The XENON10 Collaboration

Columbia University Elena Aprile (Spokesperson) , Karl-Ludwig Giboni, Maria Elena Monzani, Guillaume Plante, Roberto Santorelli and Masaki Yamashita

RWTH Aachen University Laura Baudis, Jesse Angle, Alfredo Ferella, Alexander Kish, Aaron Manalaysay and Stephan Schulte

Brown University Richard Gaitskell, Simon Fiorucci, Peter Sorensen and Luiz DeViveiros

University of Coimbra Jose Matias Lopes, Luis Coelho, Luis Fernandes and Joaquin Santos

CWRU Tom Shutt, Peter Brusov, Eric Dahl, John Kwong and Alexander Bolozdynya

Livermore National Laboratory Adam Bernstein, Norm Madden and Celeste Winant

Rice University Uwe Oberlack, Roman Gomez, Christopher Olsen and Peter Shagin

Laboratori Nazionali del Gran Sasso Francesco Arneodo and Serena Fattori

Yale University Daniel McKinsey, Louis Kastens, Angel Manzur and Kaixuan Ni

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✦ SS vessel and vacuum cryostat

✦TPC active area ~ 20 cm diameter; drift gap= 15 cm

✦ 15 kg active LXe

✦ Pulse Tube refrigerator for stable operation at –95oC

✦ 89 PMTs (R8520-06-AL): 48 in GXe and 41 in LXe

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The XENON10 Detector

Pulse tube refrigerator

15 kg LXe 89 PMTs

✦ SS vessel and vacuum cryostat

✦TPC active area ~ 20 cm diameter; drift gap= 15 cm

✦ 15 kg active LXe

✦ Pulse Tube refrigerator for stable operation at –95oC

✦ 89 PMTs (R8520-06-AL): 48 in GXe and 41 in LXe

9

The XENON10 Detector

Pulse tube refrigerator

15 kg LXe 89 PMTs

Bottom PMT Array Top PMT Array

10

The XENON10 Photo-multipliers

✦ Hamamatsu R8520-06-AL: 1-inch-square compact PMT

✦ operational at -95oC

✦ >20% QE for Xe scintillation light (175 nm)

✦ low radioactivity (U/Th/K/Co: 16/

101

102

103

104

105

106

Muo

n In

tens

ity, m

-2 y

-1

5 6 7 8 9103

2 3 4 5 6 7 8 9104

Depth, meters water equivalent

Soudan

Kamioka

Gran Sasso

Homestake (Chlorine) BaksanMont Blanc

Sudbury

WIPP

Muon flux vs overburden

NUSL - Homestake

Proposed NUSL Homestake Current Laboratories

The INFN Gran Sasso National Lab (LNGS)

(CDMS II)

(XMASS)

(XENON10)

11

3100 mwe flat overburden(surface muon flux reduced by 106)

Muo

n In

tens

ity [m

-2y-1

]

Depth [meters water equivalent]

DUSEL - Homestake

XENON10 at Gran Sasso Underground Laboratory (Italy)

12

XENON10 Detector Pb/Poly Shield

XENON10 Live-Time / Dark Matter Run Stability

13

Gamma Calibrations

Periodic Gamma Calibs

92% live

Neutron Calibration

WIMP search end

✦ High Statistics Gamma Calibs + 1 Neutron Calib

✦ NON BLIND WIMP search data ~20 live days (Sept) + 20 live days dispersed (Oct-Feb)

✦ BLIND Analysis of 60 live-day (Oct-Feb) of WIMP Search data

(2006-2007)

Signals from XENON10

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S1 S2

S1

S2

Self-shielding XENON10 Detector

15 < drift time < 65 μs, r < 80 mm (5.4 kg fiducial mass out of 15 kg) Overall Background in Fiducial Volume ~0.6 event/(kg day keVee)

15

Z (15 cm total)

near top PMTs

near bottom PMTs

Fiducial Volume

XENON10 Gamma/Neutron calibration

AmBe

Cs-137

S1 threshold (4.4 pe)

Electron Recoil Mean

Nuclear Recoil Mean

S2 threshold (300 pe) ~ 99.5 % gamma events are rejected below

nuclear recoil mean

136 kg-days Exposure= 58.6 live days x 5.4 kg x 0.86 (ε) x 0.50 (50% NR)

4.5 –27 keVr

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XENON10 WIMP Search Data

~1800 events

WIMP Search Window

136 kg-days Exposure= 58.6 live days x 5.4 kg x 0.86 (ε) x 0.50 (50% NR)

4.5 –27 keVr

17

XENON10 WIMP Search Data

~1800 events

WIMP Search Windownoise event

136 kg-days Exposure= 58.6 live days x 5.4 kg x 0.86 (ε) x 0.50 (50% NR)

4.5 –27 keVr

17

XENON10 WIMP Search Data

~1800 events

WIMP Search Windownoise event

Statistical leakage from

electron recoil band

136 kg-days Exposure= 58.6 live days x 5.4 kg x 0.86 (ε) x 0.50 (50% NR)

4.5 –27 keVr

17

XENON10 WIMP Search Data

~1800 events

WIMP Search Windownoise event

Statistical leakage from

electron recoil band

Anomalous events due to non-active Xe

Anomalous Leakage Events due to non-active LXe

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E-field

S1

e-

S1

e-e-

IncomingParticle

SensitiveVolume(15 cm)

ReverseField

Region(1.2 cm)

S1 S2no S2 !

E-field

cathode

No S2

S2

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The “anomalous events”

WIMP-Nucleon Cross-Section Upper Limits (90% CL)

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XENO

N10

CDMS

II

arXiv: 0706:0039 [astro-ph]

current results based on “Max Gap” Analysis of 10 events

(NO BKG SUBTRACTION)8.8 x 10-44 cm2 at 100 GeV

4.5 x 10-44 cm2 at 30 GeV

supersymmetry models

Upgrade XENON10 to XENON100

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Bell

Top PMTs

GridsStructure

Active LXe Shield

TeflonPanels withHVRacetracks

Shield PMTs

Vacuum Cryostat

Bottom PMTs

Active LXe Target

Cathode Mesh

Active LXe target: 70 kgActive LXe shield: 80 kgTotal LXe mass: 150 kgTo be deployed in 2008x10 better sensitivity

XENON100: Expected background rate and sensitivity

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!"#$%!&''()%*+,-.-&-(/%#&0&,-%1223 45(+6%#7).5(

89+-(%$6)59%!.'&56-.9+,%9:%;(;%?(-(@-9)%

A6''6%B6@C0)9&+D

E9F()%9:%"=(%!(5:G!H.(5D.+0IJ%'D)&

!!%$)K9,-6-L"=( M(,,(5LE8N,

B(:9)(%?.,@).'.+6-.9+

A4#;NO%89D(5

=4;>;J2!"#$%!&''()%*+,-.-&-(/%#&0&,-%1223 45(+6%#7).5(

89+-(%$6)59%!.'&56-.9+,%9:%;(;%?(-(@-9)%

A6''6%B6@C0)9&+D

E9F()%9:%"=(%!(5:G!H.(5D.+0IJ%'D)&

!!%$)K9,-6-L"=( M(,,(5LE8N,

B(:9)(%?.,@).'.+6-.9+

A4#;NO%89D(5

=4;>;J2Operating the detector for one month

(~1500 kg-d exposure) will give:

XENON100: Expected background rate and sensitivity

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!"#$%!&''()%*+,-.-&-(/%#&0&,-%1223 45(+6%#7).5(

89+-(%$6)59%!.'&56-.9+,%9:%;(;%?(-(@-9)%

A6''6%B6@C0)9&+D

E9F()%9:%"=(%!(5:G!H.(5D.+0IJ%'D)&

!!%$)K9,-6-L"=( M(,,(5LE8N,

B(:9)(%?.,@).'.+6-.9+

A4#;NO%89D(5

=4;>;J2!"#$%!&''()%*+,-.-&-(/%#&0&,-%1223 45(+6%#7).5(

89+-(%$6)59%!.'&56-.9+,%9:%;(;%?(-(@-9)%

A6''6%B6@C0)9&+D

E9F()%9:%"=(%!(5:G!H.(5D.+0IJ%'D)&

!!%$)K9,-6-L"=( M(,,(5LE8N,

B(:9)(%?.,@).'.+6-.9+

A4#;NO%89D(5

=4;>;J2

~0.01 evt/kg/keVee/day with 50-kg fiducial mass

Operating the detector for one month (~1500 kg-d exposure) will give:

Towards the discovery of Supersymmetric Dark Matter

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XENON

100 (200

8-2009)

XENON

10 (2007

)

XENON

1T (2010

+)

DUSEL?