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SIMPLE

SIMPLE. Tom Girard ( for the SIMPLE Collaboration ). SIMPLE. WIMP. Superheated freon droplet. gas. 25 m. 1 mm. ( Seitz : Phys. Fluids 1 (1979) 1 ). (i) E > E c = 4 p r c 2 g /3 e (ii)  E/  x > E c / a r c.  E/  x  150 keV/ μ m. key feature: selective sensitivity

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SIMPLE

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  1. SIMPLE Tom Girard ( for the SIMPLE Collaboration )

  2. SIMPLE WIMP Superheated freon droplet gas 25 m 1 mm ( Seitz : Phys. Fluids 1 (1979) 1 ) (i) E > Ec= 4prc2g/3e (ii) E/x> Ec/arc  E/  x 150 keV/μm • key feature:selective sensitivity • tunable (P,T) double threshold device intrinsic BG rejection < 10-10 v-a-v bolometers: 10-4,-5 xenon: 10-2 argon: 10-7,-8

  3. Instrumentation MCE-200 microphone PGA2500 adaptive amplifier 1 TB pcs (8 chl each), MatLab files of ~ 8 min (~ 4 MB) each SDD true nucleation event noise: 2-3 mV Δ : 1.6 x10-2 ms ΔV: 0.3 mV

  4. Laboratoire Souterrain a Bas Bruit [LSBB]

  5. GESA ( 60 m3) 30-100 cm thick concrete 50-75 cm thick water (shield, pool) 20 cm thick wood 1 cm thick steel 50 cm thick concrete (floor) atmospheric radon: 20 – 3000 Bq/m3 reduction :• ventilation 10x per day • top-circulation of waterpool (25 liter/min)

  6. GESA backgrounds neutron : muon : 8.6 x 102 m-2d-1 232Th (Bq/kg) 238U (Bq/kg) 40K (Bq/kg) concrete 7.7 11 57 steel 0.02 1. 8 0.02 water 7x10-5 10-4 -- (,n) + sf + (,n) shielding 1.09 ± 0.02 ± 0.07 evt/kgd  : water circulation ( 25 l/min ) diffusion radon : air 0.36 Bq/m3 0.0012 Bq/m3 internal: < 0.71 evt/kgd (radioassay) 3.26 ± 0.08 ± 0.76 evt/kgd

  7. Phase II • stage I : 14.095 kgd ( arxiv:1003.2987v2 [astro-ph.CO] 22 Mar 2010 ) • 27 October -- 14 November 2009 : SDD installation, 1 per day ( +1.9 kgd ) • 15 November 2009 – 05 February 2010 ( 12.2 kgd ) • data losses ( -4.70 kgd ) due to weather-induced power failures • stage II : ~18 kgd • 12 April – 01 May 2010: SDD installation, 1 per day ( +1.9 kgd ) • 02 May – 22 July 2010: full complement ( +15.6 kgd ) • no data losses

  8. Signal analysis protocol: • accept all signals with amplitude > 2 mV over SDD noise (4056) ( efficiency  0.97 with 95% CL or better ) • remove 2228 coincident signals ( efficiency  0.99 with 99% CL ) • freon-less SDD • any other SDD • filter remaining 1828 signals wrt • signal waveform (amplitude, decay constant,...) • FFT structure (frequency, intensity distribution...)

  9. Acoustics =?? internal external • gel fractures (81 evt) • N2 release (63) • N2 escape (4%) • gel deterioration (10%) • .... • water inlet bubbles (40%) • SDD deck motion (15%) • electronic noise (5%) • SDD “Papa” noise (10%) • human noise (5%) • .... NONE possess signal parameters or FFTs of true nucleation events  identification efficiency  97% at 95% CL

  10. “MOST Wanted” Gallery true Fenwick motion ventilation water bubbles pressure release human noise cap knocking fracture trapped N2 gas microleak

  11. RESULTS : 1828 evts total => 60 true nucleation events “true” :  = 450-750 Hz  = 5-40 ms

  12. neutron and  calibrations sound detection efficiency : 0.98 ± 0.03 Erth (9ºC) = 8.0 ± 0.1 keV 3.26 ± 0.48 evt/kgd consistent with sub-water radon level, SDD radiopurity ( acceptance  0.97 ) 0.99 ± 0.28 evt/kgd consistent with MCNP 1.09 ± 0.02 ± 0.07 evt/kgd based on material radio-assays

  13. low amplitude sector = neutrons + WIMPS How many WIMPs possible ? neutrons observed : [14 ± 3.8 ] x (1/0.98) x (1/0.97) = 14.7 ± 4.0 evt neutrons estimated:14.1 x [1.09 ± 0.02 ± 0.07] = 15.4 ± 0.28 ± 0.99evt • so • simple diff = -0.70 ± 4.1 evts • more conservative : ( max observed – min estimated ) evts expected ( [14.7 + 4.0] – [15.4 – 1.0] ) = 4.3 evt • =>up to 8 expected WIMPs at 90% CL

  14. SD ~ [ ap<Sp> + an<Sn> ]2 J-1(J+1) <Sp> = 0.441 ; <Sn> = -0.109 SD RESULTS (stage I)

  15. SI RESULTS (stage I)

  16. status & prospects • 14.1 kgd completed ( 27/10 – 05/02, losses) >with XENON10, ~ 50% reduction in allowed SD phase space • + 18 kgd completed ( 01/05 – 22/07, no losses) – under analysis • > reduce background subtraction : • > less neutrons : • xtra 10 cm wood, PE below waterpool 0.2 n / kgd • > additional radio-assays of shielding, tank water... • > prob’ly more ’s (Summer radon  1000 Bq / m3) • > further refinements in signal analysis (hi-frequency component)

  17. signal amplitudes  only this region capable of providing nucleation dE/dx neutron “big bang” “bang” N dE/dx droplet diameter (m) temperature (ºC)

  18. xtra

  19. SI rate : arXiv:astro-ph/0703543 ~ A2 but there’s also F2,

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