SIMPLETom Girard

( for the SIMPLE Collaboration )

SIMPLE

gas

25 m 1 mm

WIMP

Superheatedfreon droplet

(i) E > Ec = 4rc2/3

(ii) E/x > Ec/arc

( Seitz : Phys. Fluids 1 (1979) 1 )

E/ x 150 keV/μm

intrinsic BG rejection < 10-10 v-a-v

bolometers: 10-4,-5

xenon: 10-2

argon: 10-7,-8

• key feature: selective sensitivity

tunable (P,T) double threshold device

Instrumentation

MCE-200microphone

true nucleation event

PGA2500adaptive amplifier

1 TB pcs (8 chl each), MatLab files of ~ 8 min

(~ 4 MB) each SDD

noise: 2-3 mV

Δ : 1.6 x10-2 ms

ΔV: 0.3 mV

Laboratoire Souterrain a Bas Bruit [LSBB]

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)

GESA backgrounds

232Th (Bq/kg) 238U (Bq/kg) 40K (Bq/kg)

concrete 7.7 11 57steel 0.02 1. 8 0.02water 7x10-5 10-4 --

1.09 ± 0.02 ± 0.07 evt/kgd

neutron :

:

radon : air 0.36 Bq/m3 0.0012 Bq/m3

internal: < 0.71 evt/kgd (radioassay)

water circulation ( 25 l/min ) diffusion

(,n) + sf + (,n) shielding

muon : 8.6 x 102 m-2d-1

3.26 ± 0.08 ± 0.76 evt/kgd

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

Phase II

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...)

Acoustics = ??

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

gel fractures (81 evt)

N2 release (63)

N2 escape (4%)

gel deterioration (10%) ....

internal external

“MOST Wanted” Gallery

ventilation

cap knockinghuman noise pressure release

water bubbles Fenwick motion

microleakfracture trapped N2 gas

true

RESULTS : 1828 evts total => 60 true nucleation events

0 150 300 450 600 750 900 1050 1200 1350 1500

0

100

200

300

400

500

600

700

0

100

200

300

400

500

600

700

Am

plitu

de

(mV

)

(

ms)

Frequency (Hz)

true nucleation (1.5%) gel fracture (2.0%) acoustic (54.9%) N

2 release (1.6%)

false nucleation (0.5%)

“true” : = 450-750 Hz = 5-40 ms

2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 170,0

0,2

0,4

0,6

0,8

1,0

1,2 n calibrations (Am/Be) calibrations (U308)

norm

aliz

ed e

ven

t n

umbe

r

ln (A2)

450 500 550 600 650 700 750 800 850 900 950

102

103

104

105

106

107

n calibration calibration run (n) run ()

am

plit

ud

e2 (

mV

2)

frequency (Hz)

neutron and calibrations

3.26 ± 0.48 evt/kgd

consistent with sub-water radon level, SDD radiopurity

0.99 ± 0.28 evt/kgd

consistent with MCNP 1.09 ± 0.02 ± 0.07 evt/kgd

based on material radio-assays

sound detection efficiency : 0.98 ± 0.03 Erth (9ºC) = 8.0 ± 0.1 keV

( acceptance 0.97 )

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 ± 0.99 evt

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

-2,0 -1,5 -1,0 -0,5 0,0 0,5 1,0 1,5 2,0-2

-1

0

1

2

KIMS (3.9 ky)

COUPP (52 kgd)

PICASSO (14 kgd)

SIMPLE (14 kgd)

XENON10 (136 kgd)

NAIAD (16k kgd)

CDMS-II (121 kgd)

ap

an

ZEPLIN-III (127 kgd)

MW = 50 GeV/c2

DAMA/LIBRA

SD RESULTS (stage I)SD ~ [ ap<Sp> + an<Sn> ]2 J-1(J+1)

<Sp> = 0.441 ; <Sn> = -0.109

10 100 10001E-8

1E-7

1E-6

1E-5

1E-4

SIMPLE (14 kgd)

CRESST-II(67 kgd)

WARP(97 kgd)

KIMS(3.9 kgy)

COUPP(52 kgd)

EDELWEISS(144 kgd)

XENON10(136 kgd)

NAIAD(16k kgd)

CDMS-II(195 kgd)

ZEPLIN-III(127 kgd)

S

I

N (

pb)

MW

(GeV/c2)

SI RESULTS (stage I) max

min

v

v

22 dvv

)v(fFA~

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)

signal amplitudes

neutron

“bang”

“big bang”

dE/dx

temperature (ºC)

N

droplet diameter (m)

only this region capableof providing nucleation dE/dx

xtra

SI rate :

max

min

v

v

220 dv

v

)v(fF~Rate

~ A2

p

thrmin Am2

E~vbut there’s also F2,

arXiv:astro-ph/0703543

10 1001E-8

1E-7

1E-6

1E-5

1E-4LHe (1.2)

CRESST-II/CaWO4

31 kgd

XENON/Xe

136 kgd

Al2O

3 (2)

C4F

10 (6)

C4F

10 (8)

C4F

10 (10)

C4F

10 (16)

C4F

10 (25)

C4F

10 (50)

C4F

10 (2)

Al2O

3 (8)

SI

N(p

b)

Mw (GeV/c2)

CDMS/Ge

121 kgd