Slide 1

UK HEP Forum, May 03 UKDMC - roland lscher - RAL/PPD Double Beta Potential of Zeplin Zeplin: brief summary of DM programme Doing bb-search with a DM detector? Zeplin: brief summary of DM programme Doing bb-search with a DM detector? Can we do HDM search with CDM detectors? Very, very preliminary assessment Roland Lscher Slide 2 UK HEP Forum, May 03 UKDMC - roland lscher - RAL/PPD Direct Detection Kinematics:Kinematics: WIMP MDMD MTMT dR dE R = RoRo EorEor e -E R /E o r recoil energy incident energy kinematic factor = 4M D M T /(M D + M T ) 2 event rate per unit mass total event rate (point like nucleus) 10 8 6 4 2 -2 0 05 1015 20 25 Event Energy (keV) Event Rate (events/kg/day) Raw spectrum Noise corrected Nuclear Recoil Limits Predicted DM spectrum Background rejection tools: (1) Nuclear recoil discrimination (2) Directional signal Slide 3 UK HEP Forum, May 03 UKDMC - roland lscher - RAL/PPD Background Discrimination Nuclear recoil discriminationNuclear recoil discrimination Signal Channel Differences Ge, Si 40keV Nuclear Recoil M 200GeV v = 230km/s WIMP Scintillation Ionisation Phonon + -+ - + -+ - + -+ - + -+ - Pulse Shape Differences NaI, CsI, Xe Signal Channel Differences Xe Gamma ray (or beta decay) 40keV Electron Recoil Different dE/dX, Range, etc. Slide 4 UK HEP Forum, May 03 UKDMC - roland lscher - RAL/PPD Heavy nuclei (A~130), sensitive to spin-independent interactions (I si ~A 2 ). Isotopes with large spin-dependent factors, I sd ~0.3 for 129 Xe ( 23 Na in NaI or 73 Ge in Ge ~0.1)... as well as easier enrichement. Scintillation in UV ( =175 nm), low visible energy threshold. Large quenching factor for Xe recoils g(A)>0.2 ( I in NaI: g(A)=0.09, Na: g(A)~0.3 ), low recoil energy threshold. Low background Scintillation properties enables Pulse-Shape Discrimination (PSD) between background (electron recoil) and nuclear recoil events. Interesting ionisation properties Scale up possibilities (up to 1 ton ?) LXe: Why using it? Slide 5 UK HEP Forum, May 03 UKDMC - roland lscher - RAL/PPD ZEPLIN I Xe * +Xe Xe 2 * Triplet 27ns Singlet 3ns 2Xe 175nm Xe ** + Xe Xe 2 + +e - (recombination) Xe + +Xe Ionisation Excitation Electron/nuclear recoil Slide 6 UK HEP Forum, May 03 UKDMC - roland lscher - RAL/PPD ZEPLIN I Installation Pb shielding Top of veto Boulby stub 2 laboratory xenon purification Counts vs. time Xe temp vs. time room temp vs. time Slide 7 UK HEP Forum, May 03 UKDMC - roland lscher - RAL/PPD ZEPLIN I Energy Resolution 122 keV peak 136 keV peak (10%) 30 keV X-ray 92 keV recoil e- Linear response 1.5 - 2.5 p.e./keV ( 57 Co calibration is effective point source) Resolution 57 Co Calibration 106 keV recoil e- Slide 8 UK HEP Forum, May 03 UKDMC - roland lscher - RAL/PPD Z1 Energy Calibration Geant4 Simulation of 57 Co calibration With/without energy resolution Multi-source calibration Variation in yield commensurate with volume response matrix Slide 9 UK HEP Forum, May 03 UKDMC - roland lscher - RAL/PPD Uniformity, light collection Scan through detector girth Scan through one PMT plane Single PMT event Trigger condition is set to free-run Noise trigger Bulk events Turret events Double PMT event Fiducial volume cut Part of detector response matrixPart of detector response matrix 17% best, 14% bulk Falls to 4% below Xe delivery pipe Light collection simulations allow S3 calculationsLight collection simulations allow S3 calculations S3 cut < 0.408 (66% on 1: 0.5 + 0.5/3 )S3 cut < 0.408 (66% on 1: 0.5 + 0.5/3 ) Fiducial volume 3.1kgFiducial volume 3.1kg (excluding turrets + ~1cm below) Slide 10 UK HEP Forum, May 03 UKDMC - roland lscher - RAL/PPD cPCI DAQ system Acqiris cPCI digitizers, 1ns sampling, 8 bitsAcqiris cPCI digitizers, 1ns sampling, 8 bits Mean data rate: 2HzMean data rate: 2Hz Max rate: 800 Hz (cal)Max rate: 800 Hz (cal) Deadtime ~1 ms Dual range DAQ :Dual range DAQ : one covers high energy up to 150 keV (daily E cal) 2nd is the dark matter interval, up to 40 keV. (less digital noise at low E) Slide 11 UK HEP Forum, May 03 UKDMC - roland lscher - RAL/PPD ZEPLIN I Discrimination Using different fitting techniquesUsing different fitting techniques Exp, Mean, mean to 90%, median Fitted gamma density function in 1/Fitted gamma density function in 1/ Surface calibrations data to 7keVSurface calibrations data to 7keV Surface ambient neutrons to 4 keVSurface ambient neutrons to 4 keV Gamma source Neutron source 10-20keV Slide 12 UK HEP Forum, May 03 UKDMC - roland lscher - RAL/PPD Statistical methods 91 day livetime, 280kg.days data91 day livetime, 280kg.days data calibration from veto-ed events calibration from veto-ed events -density fit (actually in 1/ ) as guide: smooth slope -density fit (actually in 1/ ) as guide: smooth slope Analysis: 2 over signal region, poisson stat on tailAnalysis: 2 over signal region, poisson stat on tail 2 Poisson Slide 13 UK HEP Forum, May 03 UKDMC - roland lscher - RAL/PPD Standard DM modelStandard DM model Nuclear physics: Quenching = 0.2, Form factorNuclear physics: Quenching = 0.2, Form factor ZEPLIN I limit Slide 14 UK HEP Forum, May 03 UKDMC - roland lscher - RAL/PPD Dual Phase Xenon e-e- Applying an electric field Electro- luminescence Active, liquid phase Gas phase Primary-Scintillation e - or nucl. recoil Prevents (part of) recombination Measure both scintillation and ionisation Slide 15 UK HEP Forum, May 03 UKDMC - roland lscher - RAL/PPD Dual phase discrimination.. but still keeping some interesting pulse shape properties on primary Active volume: 30kg LXe Slide 16 UK HEP Forum, May 03 UKDMC - roland lscher - RAL/PPD Zeplin 3 Active volume 6kg Gas phase Inverse field region 31 PMTs Slide 17 UK HEP Forum, May 03 UKDMC - roland lscher - RAL/PPD Projected limits Slide 18 UK HEP Forum, May 03 UKDMC - roland lscher - RAL/PPD Zeplin Max - towards 1t ? Zeplin-1 type Zeplin-2 type Zeplin-3 type Modular approach ? Slide 19 UK HEP Forum, May 03 UKDMC - roland lscher - RAL/PPD Low background Scintillation properties enables Pulse-Shape Discrimination (PSD) between background (alphas) and electron recoil events. Interesting ionisation properties Scale up possibilities (up to 1 ton ?) 3 candidates to look at: 136 Xe, with E 0 = 2.48 MeV, 8.9% natural abundance 134 Xe, with E 0 = 0.85 MeV, 10.4% natural abundance 124 Xe, with E 0 = 0.82 MeV, 0.1% natural abundance Phase-space factor, hence rate, is going with E 0 5 World yearly of enriched 124 Xe is 5 liters! - - ++ LXe: Why using it? Slide 20 UK HEP Forum, May 03 UKDMC - roland lscher - RAL/PPD Gotthard experiment: 5.3kg Xe TPC 62.5% 136 Xe in 136 Xe in 136 Xe Slide 21 UK HEP Forum, May 03 UKDMC - roland lscher - RAL/PPD T 1/2 = (N A /0.136) A (M/( B)) 1/2 A: Isotopic abundance 8.9% or 65% : Detector efficiency nearly 1 M: Target mass 3.1 kg, 30kg, 250kg : Energy resolution 40 keV (p.e. statistics) 60 keV (extrapol. from low E, 1.2E) B: Background rate ? ? ? What is it in Z1? Can I extrapolate to Z2? To Zmax? Limit on 136 Xe ? Slide 22 UK HEP Forum, May 03 UKDMC - roland lscher - RAL/PPD Pulse Shape analysis at high Energy gammas Alphas (from different locations) Z1: Background at high E Slide 23 UK HEP Forum, May 03 UKDMC - roland lscher - RAL/PPD Gamma-like background: ~ exponential shape Assuming a spectroscopic smearing due to the varying light collection efficiency through the active volume - a quick back of the envelope estimate: 0.05 counts/kev/kg/year T 1/2 > 1.9 x 10 24 yr (90%CL, assuming enrichment of 65%, 1yr data) => 0.9 - 2.5 eV Dama, 6.5kg LXe DM detector, 68.8% 136 Xe : T 1/2 > 1.2 x 10 24 yr PLB, 546 (2002) 23 Gotthard, 5.3kg Gxe TPC, 62.5% 136 Xe : T 1/2 > 4.4 x 10 23 yr PLB, 434 (1998) 407 Z1: possible limit on Z1: possible limit on Slide 24 UK HEP Forum, May 03 UKDMC - roland lscher - RAL/PPD Zeplin 2: 30kg, same background rate (?) > 5.9 x 10 24 yr, < 0.5 - 1.4 eV Zeplin Max: 250kg module, same background rate (?) > 1.7 x 10 25 yr, < 0.3 - 0.8 eV To be compared with : < 0.1eV (Cuore), < 0.02 eV (Genius, EXO) (for 1 ton, 1yr) 0.35 eV (Heidelberg-Moscow claim) Competitive with large scale expt. but only if we can B (factor 10) Extrapolation to Z2 and ZMax Slide 25 UK HEP Forum, May 03 UKDMC - roland lscher - RAL/PPD Conclusion Can we do HDM search with Zeplin? May be, yes! Slight problem: isotopic enrichment would be needed buy one get, one free?!? Well, what about a free cookie? WIMP spin in/dependant cross section studies - - would require some isotopic separation! 128 Xe 129 Xe 130 Xe 131 Xe 132 Xe 134 Xe 136 Xe 1.9 26.4 4.1 21.2 26.9 10.4 8.9 Odd Even