DMTPC: A Directional Dark Matter Experiment Asher Kaboth NDM, 1 - - PowerPoint PPT Presentation

NDM, 1 Sept 2009

DMTPC: A Directional Dark Matter Experiment

Asher Kaboth

NDM, 1 Sept 2009

Why Directionality?

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Cygnus Solar System Wimp `Wind’ Galaxy Dark Matter Halo

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Signal Modulation

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z x z x 00:00 h 12:00 h Cygnus

Spergel, Phys.Rev. D37 (1988) 1353

Cygnus

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Dark Matter Recoils

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χ χ

θ

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Wire TPCs

(DRIFT)

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๏ `Grandfather’ of directional

experiments

๏ Uses negative ion drift with

CS2

๏ Has operated underground

underground at Boulby in England for several years

• !"#$ structure

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Micropattern Detectors

(NEWAGE, MIMAC)

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!"#$%&'()#*+,$-#./0&(1203

๏ Small pixelization for excellent 3D-angle

resolution

๏ Readout can be bulky and expensive ๏ Method is to use

electronic readout

• f small pixels to

reconstruct recoils

๏ NEWAGE uses

μpics; MIMAC uses micromegas

+""#$% &') !3",%-.#/+"",012!

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Emulsions

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๏ Old technology repurposed

for dark matter

๏ AgBr and gelatin emulsion

with highly improved resolution

๏ Use emulsion expansion and

• ptical microscope scanning

for track recognition

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DMTPC Collaboration

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Boston University Brandeis University Massachusetts Institute of Technology

• S. Ahlen (PI) , A. Inglis, H. Tomita
• A. Dushkin, S. Goyal, F. Golub, B. N. Skvorodnev, H. Wellenstein (PI)
• P. Fisher (PI), G. Sciolla, R. Yamamoto, D. Dujmic, R. Vanderspek,
• J. Battat, J. Monroe, S. Henderson, A. Kaboth, J. Lopez, T. Caldwell,
• A. Lee, T. Sahin, I. Wolfe, H. Yegorian

Detector Papers

• D. Dujmic et al. [DMTPC] NIMA 584 (2007)
• A. Kaboth et al. [DMTPC] NIMA 592 (2008)
• D. Dujmic et al. [DMTPC] Astropart. Phys 30 (2008)
• T. Caldwell et al. [DMTPC] arXiv:0905.2549 (2009)

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Detector Concept

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CF4 Gas

~0.1 atm

• V

+V Gnd

Drift Region 20 cm Amplification Region 0.5 mm

E

CCD PMT PMT

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Detector Concept

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• V

+V Gnd χ χ F

CCD PMT PMT

Primary Ionization and Scintillation

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Detector Concept

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• V

+V Gnd

CCD PMT PMT

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Detector Concept

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• V

+V Gnd

CCD PMT PMT

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Detector Concept

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• V

+V Gnd

CCD PMT PMT

Wavelength (nm)

200 300 400 500 600 700 800

Intensity (a.u.)

0.002 0.004 0.006 0.008 0.01 0.012 0.014 0.016

0.34 γ/e-

ACK et al. [DMTPC] NIMA 592 (2008)

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Prototype Detector

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20

• F

e-

• V

Charge readout Light readout (CCD) Light readout (CCD)

• V

Sketch of recoil length is not to scale!

0V +V 0V TAUP 2009, Rome 6

~28c

CCD readout area

cm

Minimal Materials: copper, G10, nylon, steel, fishing wire

D/µ~0.05

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Gas Measurements with CF4

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๏ Measure diffusion consistent

with previous data

๏ Drift length of 20cm for 1mm

diffusion

๏ No attenuation over 20 cm!

๏ Measure both diffusion and

attenuation with varying height sources

!

!"#"$%&

;/-$7,%1(*-$-(%/01+< :.=:>$!"#$"%&"& *1/74$3-*%8 NDM, 1 Sept 2009

Directionality

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!"#"$%& !"#"$%&

*+,-(

Bragg Peak

Total energy is given by amount of light deposited Angle and sense are given by knowledge of the energy deposition

Incident neutrons

6 mm 935 keV 550 keV 530 keV 475 keV 365 keV 313 keV

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Nuclear Head-Tail

15 Dujmic et al. Astropart. Phys. 30 (2008) arXiv:0804.4827

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Skewness

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• NDM, 1 Sept 2009

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Recoil Distribution

θ

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Exposure ~ 44 g·day Mass~3.3g (3 weeks)

Surface Background Run

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๏ Basement lab at MIT ๏ Triggerless, remote

• peration

๏ 5s CCD exposures ๏ Refill gas every 24

hours

๏ 70% live time ๏ 1% gain stability

Alphas Worms C recoils F r e c

• i

l s

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Data Without Cuts

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Preliminary

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Alphas Background

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Alpha

๏ From U, Th decays

in materials

๏ Efficiently remove

with edge cuts, range/energy

๏ Reduce with

radiopure materials

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U/Th Decay and Radon

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CF4 No data CF4 No data Rn+CF4 CF4

T1/2~4d

Constant 10 mHz rate from steel drift rings 5x reduced rate from Cu rings Radon introduced into chamber

Worm

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Worms

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μ, n γ ?

๏CCD effect ๏Remove most in

software with energy density cut

๏Reduce by going

underground, new hardware

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Preliminary Background Rate

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๏ Observe 7 recoil events in 110-200 keV range ๏ 10.8 day live-time ๏ 3.3 g detector mass

Preliminary Preliminary

! !

!"#$%&'( )*+,-./0 /)123-1/0,4+0 5046)/+7/80 /7/91):0 ;'06<=0 />?/.1/80 0@AA=B8-C: DE&&'</F0G

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Expected Sensitivity

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MSSM

!

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Going Underground

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Waste Isolation Pilot Plant

๏New 10L detector with purer materials and four cameras ๏~1600 m.w.e passive shielding and active neutron monitoring ๏Low radon contamination, < 7 Bq/m3

Site of DMTPC

Camera (1 of 4) Active Region Gas System PMT

WIMP Mass [GeV/c2] Cross-section [cm2] (normalised to nucleon)

090709085401

http://dmtools.brown.edu/ Gaitskell,Mandic,Filippini

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1

10

2

10

3

10

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• 40

10

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10

• 36

10

• 34

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Projected Sensitivity

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Xenon10 KIMS DMTPC 10 L with 50 keV threshold underground for 1 year at 100 torr MSSM CMSSM

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Scaling to 1 m3

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Four drift regions 1.2 m

Four drift regions 1.2 m camera lens pmt

WIMP mass (GeV)

2

10

3

10

)

2

(cm

p

• 41

10

• 40

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D M T P C . 1 k g

• y

C O U P P ( 2 8 ) K I M S ( 2 7 ) P I C A S S O ( 2 9 ) MSSM CMSSM

D M T P C 1 k g

• y

! !

14'5%.67"%."&'#&8%$9:;:<4:::= NDM, 1 Sept 2009

Ongoing and Future Work

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๏Use secondary detection (PMTs, charge readout) to improve

reconstruction

๏Different gas mixtures (e.g. Xe/CF4 mixes) ๏Incorporate inelastic dark matter models

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Summary

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๏ The field of directional dark matter is

expanding quickly

๏ Demonstrated operation of a CCD-

based gas detector with directional sensitivity

๏ Collected and analyzed surface run

background data

๏ Plans for underground operation at

WIPP