Rare Event Searches and the Underground

Transcription

1 Rare Event Searches and the Underground session intro cosmogenics signal background > 1

2 but...begin to see your environment! session intro direct DM detection : measurement of nuclear RECOIL events in DM-nucleus elastic scattering U,Th, K : fission, (α,n) primordials dr de R = ρ halo 2 2 v ( mt + mw ) σ 0 2 F 2 T ( m m ) m T W W v max min f ( v) v d 3 v R = N recoil WIMP N recoil neutron reduce, eliminate

3 PHASE III (AND MAYBE IV) OF THE SIMPLE DARK MATTER SEARCH EXPERIMENT AT THE LSBB TA Girard Centro de Física Nuclear & Department of Physics Universidade de Lisboa

4 Phase II - GESA 2 arrays, 15 SDDs each, ~100 day per cm water shielding

5 superheated liquids Χ superheated freon droplet gas 25 µm 1 mm ( Seitz : Phys. Fluids 1 (1979) 2 ) (i) E > E c = 4πr 2 c σ ( σ T ) + T 4 πr 3 3 c ρ v h lv 4 πr 3 3 c p (ii) de/dx > E c / Λ r c de / dx 176 kev/µm (C 2 ClF 5 ) intrinsic BG rejection

6 MOST Wanted Gallery recoil - α discrimination Power [db] Hz particle-induced event PSD [db] mhz Fenwick GESA door closed normalized event number (%) neutron calibrations gap α calibrations Frequency [Hz] Frequency [Hz] 20 Fenwick motion Human noise in GESA 10 Ventilation on ln (A 2 ) mhz mhz Water bubbles in the bath PSD [db] Hz PSD [db] khz PSD [db] X: 1488 Y: Frequency [Hz] human noise Frequency [Hz] ventilation Frequency [Hz] water bubbles Hz Hz khz Power [db] Power [db] Power [db] Frequency [Hz] fracture Frequency [Hz] trapped N2 gas Frequency [Hz] microleak

7 Phase II 2014 : spin-independent results 1E-3 (a) PICASSO dr de DAMA/LIBRA R ρ 2m halo 2 T σ M N W A 2 T F v 2 T v max min f ( v) v d 3 v 1E-4 (b) CoGeNT ( SIMPLE-2012 ) σ SI (pb) N 1E-5 1E-6 SIMPLE-2014 KIMS COUPP ZEPLIN-III EDELWEISS CDMS-II 1E-7 CRESST-II XENON M W (GeV/c 2 )

8 Phase II 2014 : spin-dependent (proton) 10 0 dr de COUPP 2012 PICASSO kg, 437 kgd 0.9 kg, 114 kgd R ρ σ halo = 2 2µ M p, n W S T 2 F v 2 T v max min f ( v) v d 3 v 10-1 KIMS kg, kgd (SIMPLE 2012) σ SD (pb) p IceCube 10-2 SIMPLE kg, 18.3 kgd SuperK M W (GeV/c 2 )

9 SIMPLE C 2 ClF 5, or C 3 F 8, C 4 F 10, C 4 F 8, CF 3 I gel: < 0.5 evts/kgf/day glass, etc: < 0.5 evts/kg/d ~ 100 d lifetime cost : ~ 50 instrumentation: ~10 k (16 chnl) ~ g C 2 ClF 5 per device too small filling factor

10 SIMPLE Phase III ( bubble chambers to increase active mass ) ( BDC: J. Puibasset, 2000 ) gel glycerol superheated liquid

11 Prototype BDC nº 1 ( ~0.5 kg ) (with piston recompression) distribution of BDC recompression time intervals recompression frequency time interval between recompressions (min)

12 acoustic check (2012) mhz khz khz khz khz khz khz khz khz khz x x 10 4

13 Prototype BDC nº 2 ( ~ 1 kg ) gas bubble drift chamber V liquid

14 recompression system C & C (= 2 hydraulics) hydraulics pistons

15 Prototype BDC nº2

16 Prototype BDC nº3 ( ~ 0.8 kg)

17 recompression performance prototype BDC nº3, C 4 F 8 recomp distance = 5 m trigger threshold = 100 mbar

18 pressure acoustic correlation raw filter d x khz FFT x 10 4

19 Phase III concept (in GESA) HDPE water (pure) waterbox (pure) waterbox (normal) wood 3.1 m BDC temperature pressure acoustic instr m

20 TABLE 2: materials radioassays material 232 Th (Bq/kg) 238 U (Bq/kg) BC contribution (evt/kgd) rock concrete x 10-3 steel/metal 1.3 x x 10-3 ~ 0 water (dirty) 5.0 x x x 10-4 water (clean) 5.0 x x x 10-5 wood 3.0 x x x 10-5 PE 2 x x x 10-5 plastics x 10-3 paraffin < 0.41 < x 10-5

21 Radio-assays, chamber plastics: Results for U impurities: inequalities denote upper limits on the measurements; Bg = background contribution to an experiment, estimated from Phase II construct. replace

22 Production BDC nº4 ( ~ 0.7 kg ) C 2 ClF 5 (12ºC, 2 bar) E min = 5 kev C 3 F 8 (10ºC, 1 bar) E min = 3 kev

23 Neutron Shield installation in GESA initiation construction raising the walls inner waterboxes: purified H20 outer waterboxes: tap water

24 HOW ever problems: recompression and acoustic readout. fixed +/- fixed

25 ... a SIMPLE Phase IV?? 20x 50 liter BDC 2m surrounding purified water => 1200 m 3 ~ 20 GESA s BG ~ 1 recoil event/ year, people, site?? ~ 3 M

26 ... e.g. in the LSBB Capsule?... remove cabine flood to ~ ½ Ø (5 m) 10 6 more neutron suppression 10x recomp systems - 2x 20x LF acoustic (2 pc) - 1-2x temp. controller -.?

27 SUMMARY : SIMPLE Phase III - has working BDCs - 4 to be installed underground, w/ new shielding (1 1.5m water thickness 4π, inner 2 ton resin-purified) - expected turn-on (depends on, team) SIMPLE Phase IV - 20x 50 liter BDC + 2m purified water 4π - site? proposal to ERC not funded 2013 initiation proposal (Portugal) not funded -..??