DMTPC: A Directional Dark Matter Experiment Asher Kaboth NDM, 1 Sept 2009
Why Directionality? Dark Matter Halo Galaxy Solar System Cygnus Wimp `Wind’ NDM, 1 Sept 2009 2
Signal Modulation z 12:00 h x Cygnus z x 00:00 h Spergel, Phys.Rev. D37 (1988) 1353 NDM, 1 Sept 2009 3
Dark Matter Recoils Cygnus χ χ θ NDM, 1 Sept 2009 4
Wire TPCs (DRIFT) ๏ `Grandfather’ of directional experiments ๏ Uses negative ion drift with CS 2 ๏ Has operated underground underground at Boulby in England for several years NDM, 1 Sept 2009 5
� � � � � � � � � � � Micropattern Detectors � � � � � � � � � � � � � � �� � �� � � � � � � � � � �� � �� � � � � � � � �� � � � � � � � � (NEWAGE, MIMAC) !"#$ structure ๏ Method is to use electronic readout of small pixels to reconstruct recoils ๏ NEWAGE uses μ pics; MIMAC uses micromegas ๏ Small pixelization for excellent 3D-angle resolution ๏ Readout can be bulky and expensive !"#$%&'()#*+,$-#./0&(1203 NDM, 1 Sept 2009 6
Emulsions ๏ Old technology repurposed &' ) !3",%-.#/+"",012 ! for dark matter ๏ AgBr and gelatin emulsion with highly improved resolution +""#$% ๏ Use emulsion expansion and optical microscope scanning for track recognition NDM, 1 Sept 2009 7
DMTPC Collaboration Boston University S. Ahlen (PI) , A. Inglis, H. Tomita Brandeis University A. Dushkin, S. Goyal, F. Golub, B. N. Skvorodnev, H. Wellenstein (PI) Massachusetts Institute of Technology P. Fisher (PI), G. Sciolla, R. Yamamoto, D. Dujmic, R. Vanderspek, J. Battat, J. Monroe, S. Henderson, A. Kaboth, J. Lopez, T. Caldwell, A. Lee, T. Sahin, I. Wolfe, H. Yegorian Detector Papers D. Dujmic et al. [DMTPC] NIMA 584 (2007) A. Kaboth et al. [DMTPC] NIMA 592 (2008) D. Dujmic et al. [DMTPC] Astropart. Phys 30 (2008) T. Caldwell et al. [DMTPC] arXiv:0905.2549 (2009) NDM, 1 Sept 2009 8
Detector Concept PMT CCD PMT -V CF 4 Gas Drift Region E ~ 0.1 atm 20 cm Gnd Amplification Region +V 0.5 mm NDM, 1 Sept 2009 9
Detector Concept PMT CCD PMT -V χ χ F Primary Ionization and Scintillation Gnd +V NDM, 1 Sept 2009 10
Detector Concept PMT CCD PMT -V Gnd +V NDM, 1 Sept 2009 11
Detector Concept PMT CCD PMT -V Gnd +V NDM, 1 Sept 2009 11
Detector Concept PMT CCD PMT -V ACK et al. [DMTPC] NIMA 592 (2008) Intensity (a.u.) 0.016 0.34 γ /e - 0.014 0.012 0.01 0.008 0.006 0.004 Gnd 0.002 +V 0 200 300 400 500 600 700 800 Wavelength (nm) NDM, 1 Sept 2009 11
Prototype Detector Minimal Materials: Light readout copper, G10, (CCD) nylon, steel, fishing wire -V � F e - 0V +V Charge 0V readout CCD ~28c -V readout cm area Light readout (CCD) Sketch of recoil length is not to scale! 20 TAUP 2009, Rome 6 NDM, 1 Sept 2009 12
Gas Measurements with CF 4 ๏ Measure both diffusion and attenuation with varying height sources D/ µ ~0.05 ๏ Measure diffusion consistent with previous data ๏ Drift length of 20cm for 1mm diffusion ๏ No attenuation over 20 cm! NDM, 1 Sept 2009 13
Directionality *+,-( Bragg Peak Angle and sense !"#"$%& are given by knowledge of the energy deposition !"#"$%& !"#"$%& ;/-$7,%1(*-$-(%/01+< :.=:>$ !"#$"%&"& Total energy is given *1/74$3-*%8 by amount of light deposited ! NDM, 1 Sept 2009 14
Nuclear Head-Tail 935 keV 550 keV Incident neutrons 530 keV 475 keV 365 keV 313 keV 6 mm Dujmic et al. Astropart. Phys. 30 (2008) arXiv:0804.4827 NDM, 1 Sept 2009 15
Skewness NDM, 1 Sept 2009 16
Recoil Distribution θ � NDM, 1 Sept 2009 17
Surface Background Run ๏ Basement lab at MIT Exposure ~ 44 g·day ๏ Triggerless, remote Mass~3.3g operation (3 weeks) ๏ 5s CCD exposures ๏ Refill gas every 24 hours ๏ 70% live time ๏ 1% gain stability NDM, 1 Sept 2009 18
Data Without Cuts C recoils Alphas s l i o c e r F Preliminary Worms NDM, 1 Sept 2009 19
Alphas Background ๏ From U, Th decays in materials ๏ Efficiently remove with edge cuts, range/energy Alpha ๏ Reduce with radiopure materials NDM, 1 Sept 2009 20
U/Th Decay and Radon Radon introduced into chamber CF 4 No data Rn+CF4 No data CF 4 CF 4 T 1/2 ~4d Constant 10 mHz rate from 5x reduced rate steel drift rings from Cu rings NDM, 1 Sept 2009 21
Worms μ , n γ ? ๏ CCD effect ๏ Remove most in software with energy density cut Worm ๏ Reduce by going underground, new hardware NDM, 1 Sept 2009 22
Preliminary Background Rate Preliminary Preliminary ๏ Observe 7 recoil events in 110-200 keV range ๏ 10.8 day live-time ๏ 3.3 g detector mass NDM, 1 Sept 2009 23
Expected Sensitivity !"#$%&'( )*+,-./0 /)123-1/0,4+0 5046)/+7/80 /7/91):0 ;'06<=0 />?/.1/80 0@AA=B8-C: DE&&'</F0G MSSM ! ! NDM, 1 Sept 2009 24
Going Underground W aste I solation P ilot P lant Camera (1 of 4) PMT Active Region Site of DMTPC Gas System ! ๏ New 10L detector with purer materials and four cameras ๏ ~ 1600 m.w.e passive shielding and active neutron monitoring ๏ Low radon contamination, < 7 Bq/m 3 NDM, 1 Sept 2009 25
Projected Sensitivity -34 10 Cross-section [cm 2 ] (normalised to nucleon) http://dmtools.brown.edu/ Gaitskell,Mandic,Filippini Xenon10 -36 10 DMTPC 10 L KIMS with 50 keV threshold underground -38 10 for 1 year at 100 torr -40 10 MSSM CMSSM -42 10 090709085401 1 2 3 10 10 10 WIMP Mass [GeV/c 2 ] NDM, 1 Sept 2009 26
Scaling to 1 m 3 ) ) 9 0 2 0 2 ( O (cm S S A C I P -36 ) 8 0 10 0 2 ( P camera P U O C ) 7 p 0 0 2 lens ( S � M I K -37 10 pmt y - g k 1 . 0 C P T M D -38 10 Four drift Four drift regions -39 10 regions MSSM -40 10 y - g k 0 0 1 C P T M D -41 10 CMSSM 1.2 m 1.2 m 3 2 10 10 WIMP mass (GeV) NDM, 1 Sept 2009 27
Ongoing and Future Work ๏ Use secondary detection (PMTs, charge readout) to improve reconstruction ๏ Different gas mixtures (e.g. Xe/CF 4 mixes) ๏ Incorporate inelastic dark matter models 14'5%.67"%."&'#&8%$9:;:<4:::= ! ! NDM, 1 Sept 2009 28
Summary ๏ 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 NDM, 1 Sept 2009 29
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