Neutrino Backgrounds to Dark Matter Searches and Directionality

Neutrino Backgrounds to Dark Matter Searches and Directionality

Neutrino Backgrounds to Dark Matter Searches and Directionality

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DirectionalityDrukier, Freese, Spergel,Phys. Rev. D33:3495(1986)If DAMA/LIBRA annual modulation(1-2%) due to WIMP wind...Bernabei @ NO-VE, arXiv:0804.2741… search for much larger(30-100%) diurnal oscillationsin WIMP directionSpergel, Phys. Rev. D37:1358 (1988)need to measure bothrecoil energy and angleJocelyn Monroe May 30, 2008

Directionality PotentialS. Henderson, JM, P. Fisher,arXiv:0801.1624(i) sensitivity in the presence ofbackgrounds better for 2D vs. 1D1D, Poisson1D, Gap2D, Patch(ii) search for dark matter sky anisotropy,90% CL detection requires 5-100 eventsA. M. Green, B. Morgan, astro-ph/0609115Jocelyn Monroe May 30, 2008

Dark Matter TPC CollaborationBoston UniversityS. Ahlen, D. Avery*, M. Lewandowska,K. Otis, A. Roccaro, H. TomitaMITO. Bishop, B. Cornell * 1) , D. Dujmic,W. Fedus * , P. Fisher, S. Henderson,A. Kaboth, J. Monroe, T. Sahin * ,G. Sciolla, R. Vanderspeck,R. Yamamoto, H. Yegoryan *Brandeis UniversityH. Wellenstein. N. Skvorodnev*) undergraduate student, 1) Harvard U.Jocelyn Monroe May 30, 2008

DM-TPC: 2nd Generation PrototypeSurface operation at BU:• 256 um mesh pitch• 30 um wire diameter• 79% transparency23 cm11Apogee U2 CCDJocelyn Monroe May 30, 2008

Particle ID:Range vs. EnergyNuclear recoils fromCf-252 exposureRange vs. ionization energyvery different for electronsvs. nuclear recoilsMCdataγ e - ➙γe - rejection>1e6 from Cs137 calibration(MC)(MC)13 keV electrons40 keVnuclearrecoils15 keValphas(MC)Jocelyn Monroe May 30, 2008

Spin-Dependent Dark Matter Cross Section ReachFluorine spin factor:λ 2 J(J+1) ~ 0.65PRELIMINARYSENSITIVITY0.1kg-y improves limits100kg-y tests MSSMAssumes background of 1 ev/kg/100 daysnext steps: 1 m 3 detector + low backgroundmaterials = basic module for large detector,R&D undergroundJocelyn Monroe May 30, 2008

Directionality FutureEventually: large detector, 10 -46 cm 2 sensitivity,sited at DUSEL?MiniBooNE:6 x 6 x 6 m 3DMTPC:16 x 16 x 16 m 3 MINOS:1 ton of CF 4@50Torr13 x 15 x 30 m 3 SNO:21 x 21 x 34 m 3SuperK:40 x 40 x 40 m 3detector size for 100 kg CF 4 @ 50 Torr10 -39 cm 2 spin-dependent sensitivity (tests MSSM)10 -44 cm 2 spin-independent sensitivity (current SI experiments)Jocelyn Monroe May 30, 2008

Directional detection is a powerfulnew way to search for dark matter.Backgrounds make directional detection very attractive.Coherent scattering of solar νs is an irreducible backgroundto ton-scale, O(keV) threshold dark matter searches without direction.Huge progress experimentally in last few years:first directional experiment (DRIFT), first directional limit (NEWAGE),first observation of vector direction in low-energy nuclear recoils (DMTPC)Dark matter telescope:transition from discovery to observatory.Jocelyn Monroe May 30, 2008

BackupJocelyn Monroe May 30, 2008

Dark Matter Windkinetic energy dissipationby baryons+conservation ofangular momentum L = m (v x r)=a difference in velocity betweenbaryons and dark matter...appearsto “blow”fromCygnusJocelyn Monroe May 30, 2008

OptimizationNumber of events to detect thedark matter wind:how many events to detectthe dark matter wind?No background, 3-d vector read-out, ET = 20 keVDetector Properties:detector resolutionenergy thresholdbackgroundreconstruction(2D vs. 3D)vector or axialreconstructionA. M. Green, B. Morgan, astro-ph/0609115Jocelyn Monroe May 30, 2008

Signals in Directional Detectors1)distribution of signal events determined by:1. angular resolution of elastic scattering2. dark matter velocity dispersion+2)=Jocelyn Monroe November 8, 2007

DRIFTOperating in Boulby (UK),wire readout, 40 torr CS 2 gas,negative ion drift,16 kg-day exposurehead-tail for ~5 MeV alphasJocelyn Monroe November 8, 2007

DRIFTCurrently radon limited(~10 3 events/kg/day)can distinguish differentparts of the Rn222 decaychain by rangeDrift Collaboration, accepted forpublication in AstroPart. Phys.expected nuclearrecoil signalrange ~mmJocelyn Monroe November 8, 2007

NEWAGEOperating in Kamioka (Japan),μ-pattern gas detector readout,100 torr CF 4 gas, e - drift,e- rejection: < 2E-4100 keV recoil thresholddemonstratedaxial 3D trackreconstructionwith 252 Cf sourceJocelyn Monroe November 8, 2007

NEWAGEfirst directional detector limit!surface run, 0.15 kg-day exposure,spin-dependent cross sectionK. Miuchi, et al., Phys.Lett.B654:58-64 (2007)Jocelyn Monroe November 8, 2007

ν Coherent ScatteringQ 2 = 2mT, low Q 2 simplifies nuclear description(to 1st order no Q 2 dependence except in form factor)()dσdT = G2 F (¯hc)2 m 2 (nucleusN − (1 − 4sin 2 θ W )Z 1 − m )nucleusT nucleus4π2Eν2 F(Q 2 ) 2N = number of target nucleonsZ = number of protonsF(Q 2 ) = nuclear form factor- cross section ~ N 2 , heavier nucleus = more events- as T nucleus increases, cross section decreasesD. Z. Freedman, PRD 9, 1389 (1974);H. T. Wong, et al., J. Phys. Conf. Ser. 39, 266 (2006);K. Scholberg, PRD 73, 033005 (2006)Jocelyn Monroe May 30, 2008

ν Fluxes (cm -2 s -1 )Considered hereSource Predicted Eν RangeSolar Total O(1E13)

Prediction vs. MeasurementSolar ν:PredictedΦ(B 8 ) = 5.86 x 10 6 cm -2 s -116% normalization uncertaintyhttp://www.sns.ias.edu/~jnb/SNdata/sndata.htmlMeasuredSNO: 1.09 x predicted (10%)SK: Φ(B 8 ) uncertainty = 3.5%Geo ν:Φ(U 238 ) = 2.34 x 10 6 cm -2 s -1Φ(Th 232 ) = 1.98 x 10 6 cm -2 s -1http://www.awa.tohoku.ac.jp/~sanshiro/geoneutrino/spectrum/index.htmlKamLAND: ~4 x predicted,76% measurement uncertaintyAtm ν:Φ(U 238 ) = 9.6 x 10 -1 cm -2 s -1(geomagnetic cutoff important)20% normalization uncertaintySuperK: normalization within10% of prediction (+ osc.) forEν

First GenerationDetector PrototypeCCD CameraKodak KAF0401 chip768x512 (9x9um)Cooled (-20C)Photographic lens (55mm)Finger Lakes InstrumentationCF 4gas100-380TorrDrift region:2.6cm, E=580V/cmAmplification region:Anode: 5mm pitch, 100μmGround: 2mm pitch, 50μmJocelyn Monroe May 30, 2008

Cf-252 CalibrationSoft energy spectrum:most neutrons below ~4 MeV alphaproduction thresholdEnergy and recoil angle distributionssimilar to dark matter induced recoils100keV recoil angleSource14.1 MeVneutronsNeutrons fromCf252200GeV WIMPneutronenergyRecoil angle80deg~57deg (avg)~43deg (avg)neutronenergyrecoil FenergyJocelyn Monroe May 30, 2008

Track AnalysiscountsXprojectionYprojectionyxxRange: count # of pixels above thresholdMeasured along track direction (+/- 3 pixels around track),background estimate from neighboring pixels.Energy: integral of light yield on the wireMeasured perpendicular to track direction, in +/- 5 pixelsaround segment, Gaussian fit above flat background.Jocelyn Monroe May 30, 2008

Amplification and GainMesh amplification planes with copper anode: gain 1-2x10 4developing transparent electrodes for double-sided readout1mCalibrate gain, energy with5.5MeV α’s from Am-241•CCD: ~15-45 counts/keV•ΔE/E: ~10%•spatial resolution: ~400 um•stability: ~1/2 day(without flowing gas)•Jocelyn Monroe May 30, 2008

Scintillation YieldA. Kaboth, et al., arXiv:0803.2195ratio of scintillation to ionizationdetermines signal amplificationcountsresult: γ/e - = 0.34 +/- 0.04= 6,000 photons/MeVCCDrangePhotonSignalOutspectrum of CF 4 scintillationdetermines CCD signal acceptanceresult: CF4 dark matter target wellmatched to CCD readoutJocelyn Monroe May 30, 2008

DiffusionCritical parameter:nuclear recoil range ~ mm0.5cm 1.05cm 1.6cm 2.05cmMeasure with alpha sourcesat different heights in driftregion (Δz)200Torrσ[µm] = 324 ⊕ 36 ΔzD. Dujmic, et al., NIM A 584:337 (2008)€340μm for Δz=1cm670μm for Δz=25cmMaximum size of drift regionJocelyn Monroe May 30, 2008

RangeCalibration280Torr of CF 45.5MeV alpha tracks340TorrBragg peak280Torrfit for endpoint280TorrData vs. SRIM300Torr320Torr340Torr360Torr380Torrrangecalibrationrelative to SRIMsimulationJocelyn Monroe May 30, 2008

Thresholdcurrently head-tail quality factor>50% above ~120 keVNow:Q HT10.8with reasonable improvements ingain, expect to lower 50% fractionto 80 keVGEANT4CFαe - 200 300 400 500E (keV)now vs. future:75 vs. 50 Torr, 25 vs. 60 ADU/keV,3x less CCD noise, 1 vs. 2-drift readoutJocelyn Monroe May 30, 2008

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