SNOLAB WORKSHOP OCT V. Zacek Université de Montréal Project overview Progress report Milestones and Schedule Infrastructure needs Personnel & HQP Outlook

Université de Montréal, Queen’s University, University of Alberta, Laurentian University, University of Indiana, South Bend, SNOLAB, CTU Prague, Bubble Technology Industries

Enhancement factor Neutralino interaction with matter: Depending on the type of target nucleus and neutralino composition Spin independent interaction (C A  A 2 ) Spin dependent interaction C A = (8/  )(a p + a n ) 2 (J+1)/J n3/2 131 Xe p5/2 127 I 0.084n1/2 29 Si n9/2 73 Ge 0.011p3/2 23 Na 0.863p 1/2 19 F 0.11p3/2 7 Li 2 UnpairedSpinIsotope Spin of the nucleus is approximately the spin of the unpaired proton or neutron Active Target C 4 F 10

Comparison SD and SI - searches no channel favoured largely uncorrelated destructive interference possible in SI sector Need to explore both sectors!

Spin Dependent Sector (TAUP ’07) KIMS: 3403 kgd NAIAD: kgd PICASSO: 22 kgd SM predictions O(10 -3 pb)

 Superheated droplets at ambient T & P *  150  m droplets of carbofluorides dispersed in polymerised gel  Active liquid: C 4 F 10 T b = o C)  Radiation triggers phase transition  Events recorded by piezo-electric transducers * Inspired by personal neutron Bubble Technology Industries, ON

Main Features - each droplet is an independent “clean” Bubble Chamber - keV threshold for DM induced recoils - with full efficiency for nuclear recoils - excellent gamma & MIP at E rec = 5 keV - continuous operation 30h - recompression recycles burst droplets - low cost, with potential for a large DM experiment - in house fabrication 1 st generation: 10 mL 2 nd generation : 1L 3 rd generation : 4.5L

Detector Response 226 Ra spike (200  m Ø)

Detector Response 226 Ra spike (200  m Ø) AcBe neutrons (data +MC)

Detector Response 226 Ra spike (200  m Ø) AcBe neutrons (data +MC) Recoil nuclei from 50 GeV WIMP

Detector Response Gamma & MIP rejection better above E rec = 10keV! 226 Ra spike (200  m Ø) AcBe neutrons (data +MC) Reoil nuclei from 50 GeV WIMP  & MIP response

2.6 kg PHASE Critical item at the moment: ADC boards! 20 / 32 installed 4 more ready; 8 to be debugged (soldering accident) 32 detectors  2.6 kg of C 4 F acoustic R/O channels 3D event localization 20 detectors running another 8 detectors u/g ; 4 UdeM to ship analysis in progress publication of intermediary results in prep.

Temperature & Pressure Control System (TPCS) - TPCS units - temp. precision: ± C - 4 detectors /TPCS - 40 h data taking - 15 h recompression

Data Analysis filter events (high pass) Integrate Ampl. 2 time frequency analyis spike cuts Compare to known backgrounds 

Sensitivity (22 kgd ) PRELIMINARY

’07 ’08 ’09 ’10 ’ kg 32 modules Data taking 8 –16 modules Data taking 20 modules Preamps, DAQ boards Installation + 12 modules Data taking 32 modules R&D  backg. / kg * (backg./100) Data taking 32 modules R&D 30L mod. high ldg. Phase II 25 kg 30L detector prod. Data taking Ladder Lab ? Timeline & Milestones 700 kgd 7000 kgd * Present background of cts g -1 h kgd pb pb 0.06 pb*

Scientific Reach 2.6 kg Phase (ongoing) 700 kgd Bckg cts h -1 g kg * 700 kgd Bckg: 3x10 -5 cts h -1 g kg Phase 000 kgd 30L modules Backg.: 3x10 -5 cts h -1 g -1 Spin Dependent Sector MSSM

Infrastructure needs On site support extremely helpful (I. Lawson)  short interventions, change electronics, assistance before/ after power outages measuring time at HP(Ge)  regular assays of samples || to detector fabrication Office space / cubicles  with full installation c.o.g. shifting to SNOLAB Radiochemistry and low background expertise  SNOLAB (Laurentian) radio chemistry lab for spike work Electronics maintenance support from technician (Reg, Noël) Computing support for on-line servers and network Clean lab space for sample preparation

Discrimination of Nuclear Recoils from Alpha Particles Average of peak amplitudes of nine transducers / detector High pass filter with cut-off at 15 KHz PICASSO discovered a significant difference between amplitudes of neutron and  - particle induced events ! Accepted for pub. In New Journal of Physics arXive: Signals carry information about first moment of bubble formation n-calibration  - background

Discrimination of Nuclear Recoils from Alpha Particles Are these really  events? PICASSO discovered a significant difference in amplitudes between neutron and   - particle induced events ! Accepted for pub. In New Journal of Physics arXive: Signals carry information about first moment of bubble formation  -like Temperature response!

Discrimination of Nuclear Recoils from Alpha Particles PICASSO discovered a significant difference between amplitudes of neutron and  - particle induced events ! Accepted for pub. In New Journal of Physics arXive: Why not observed earlier? Previous detector had smaller droplets! now 200  m compared to < 10  m range of nuclear recoils < L c but range of alphas >> L c many bubbles can form on  track (depend on temperature)

Nuclear recoil: point like, strong ionisation  -particles: ionization on 35  m track  # prim. bubbles Poisson distributed !  - n Discrimination: a tentative explanation # of primary bubbles = 1 = 4 = 8 # of bubbles created T = 30 0 C T = 40 0 C T = 50 0 C LcLc LcLc LcLc (in MIP sensitive region: T = 60 0 C  > 20 bubbles) 1

 - n Discrimination: Temperature Dependence Strong saturation of raw signals above 30 0 C!

From bubble chamber operation:  bubble density  dE/dx   bubble density strongly increases with T  Plesset-Zwick theory:  bubble growth   pressure amplitude  acceleration & temperature   first 50  s of signal preserve  m resolution of prim. event  - n Discrimination: Discussion Next: increase discrimination by controlling gain  new pulser increase resolution by using 3D info eliminate saturation effects by reducing gain run at one temperature only ! (45 0 ?) Very exciting!

Ultra Pure Water system (18.2 MΩ ⇔ 0.2ppb) Detector Fabrication Well organized, timed and rapid! Chain production of 3 –4 detectors / working day Large droplets (  200  m Ø) CsCl loaded matrix replaced by hydrocarbon based version  intrinsically much cleaner in U/Th !!  performance issues under investigation

3. Imaging the sample Determination of Droplet Size (L.U.) Tracing the droplets Droplet size distribution (volume) 2400 droplets gel sample: 0.7 mL Analyze gel from more detectors and compare Continue development of nondestructive method

 Calibration with mono-energetic neutrons  neutron induced nuclear recoils similar to WIMPS  n-p reactions on 7 Li and 51 V targets at 6 MV UdeM-Tandem  threshold measurements in the sev. keV region Progress in Test Beam Calibration Detection efficiency (T)Neutralino response (T)

Lithium ( 7 Li) Vanadium ( 51 V) 528 keV 40 keV Previous measurements: 7 Li target 200 keV < E n < 5000 keV. New measurements: 51 V target 5 keV < E n < 90 KeV Target selection

Check of resonance in V-target Five 51 V resonances: 97, 61, 50, 40 and 5 keV

Improved Calibration of the Detector Response 51 V resonances 7 Li data Theory

Monte Carlo Simulations Response at threshold not a step function!  - increases with neutron energy! Test beam New! AmBe source (u/g calib.)

COLLABORATION DEMOGRAPHY Present compostion MSc students: 5 PhD students: 1 Ugrad. lab students 2 (IUSB) Postdocs: 3 Researchers and faculty: 10 (4 FTE) Engineers (electr.) 1 Technicians 4 Careers & Training: completed MSc theses: 11 (4 in ’08) completed PhD theses: 4 (2 in ’08) RA  faculty: 2 U. Wichoski (UdeM  L.U.) C. Krauss (Q.U.  U.A.) > 30 summer students during the last six years > 6 “stage” students from France (région Rhône Alpes)

Distribution of Tasks Montréal: - electronics, DAQ, analysis - detector fabrication + R&D - calibration, quality control Queen’s: - slow control (T&P), u/g install. + coordination - on-line monitoring, DAQ, analysis - detector fabrication, purification +R&D Alberta: - slow control, u/g install., electronics - analysis + coordination Laurentian: - det. characterization, purification, u/g install. SNOLAB: - HP(Ge) assays, on-site support (I. Lawson) Indiana: - piezo transducer fabrication, quality control Prague: - detector container fabrication / Monte Carlo

PICASSO - COUPP - MOU

SD SI PICASSO/COUPP  Joint Strategy for 100kg Detector? PICASSO / COUPP eventually also SI interactions?

Summary 2.6 kg Phase with 32 detectors nearly completed 20 of 32 detectors installed; 28 u/g; 31 modules ready Upgrade gradually with cleaner detectors  “saltless” detectors New discovery of n -  discrimination Physics results to be published soon Complete Phase 1 with 700 kgd in 2009 R&D on purification (1/100) and 30L detectors prepare 25 kg phase  7000 kgd

1952 Donald Glaser: “Some Effects of Ionizing Radiation on the Formation of Bubbles in Liquids” (Phys. Rev. 87, 4, 1952) 1958 G. Brautti, M. Crescia and P. Bassi: “A Bubble Chamber Detector for Weak Radioactivity” ( Il Nuovo Cimento, 10, 6, 1958) 1960 B. Hahn and S. Spadavecchia “Application of the Bubble Chamber Technique to detect Fission Fragments” (Il Nuovo Cimento 54B, 101, 1968) 1993 “Search for Dark Matter with Moderately Superheated Liquids” (V.Z., Il Nuovo Cimento, 107, 2, 1994) Superheated Liquids For Particle Detection Superheated Liquids & Dark Matter: SIMPLE, COUPP, PICASSO

Detector Response  neutrons WIMPS MIPS

Detector Response B. Hahn, Il Nuovo Cimento, 1961, Vol. 22, 650