1. SNO+ Mark Chen Queen’s University Neutrino Geophysics, Honolulu, Hawaii December 15, 2005

2. 1000 tonnes D 2 O 12 m diameter Acrylic Vessel 18 m diameter support structure; 9500 PMTs (~60% photocathode coverage) 1700 tonnes inner shielding H 2 O 5300 tonnes outer shielding H 2 O Urylon liner radon seal depth: 2092 m (~6010 m.w.e.) ~70 muons/day Sudbury Neutrino Observatory

3. Depth Matters!

4. SNO Timeline 199819992000200120022003200420052006 commissioning Pure D 2 O Salt Pure D 2 O and desalination 3 He Counters NOW added 2 ton of NaCl pure D 2 O phase discovers active solar neutrino flavors that are not e salt phase moves to precision determination of oscillation parameters; flux determination has no spectral constraint (thus can use it rigorously for more than just the null hypothesis test) – day/night and spectral shape are studied as well as the total active 8 B solar neutrino flux NCDs installed and taking production data; final SNO configuration offers CC and NC event-by-event separation, for improved precision and cleaner spectral shape examination ?

5. Fall 04 to Dec 06: SNO Phase III – 3 He proportional counter array dedicated Neutral Current Detectors (NCDs) taking production data –data taking end date: 31 Dec 2006 will bring total uncertainty on 8 B solar NC signal below 5% –physics with heavy water will be complete –heavy water will be returned to AECL in 2007 what should be done next? Beyond SNO

6. SNO plus liquid scintillator → physics program –pep and CNO low energy solar neutrinos tests the neutrino-matter interaction, sensitive to new physics –geo-neutrinos –240 km baseline reactor oscillation confirmation –supernova neutrinos –double beta decay? Fill with Liquid Scintillator

7. SNO+ Technical Issues  liquid scintillator selection compatibility with acrylic vessel compatibility with acrylic vessel high light yield, long attenuation length high light yield, long attenuation length  reversing the acrylic vessel mechanics SNO: AV contains heavy water, must hold up SNO: AV contains heavy water, must hold up SNO+: AV contains scintillator,  < 1 g/cm 3, must hold down SNO+: AV contains scintillator,  < 1 g/cm 3, must hold down  liquid scintillator purification

8. Acrylic Vessel Hold-down “rope net” being designed to hold down 15% density difference (buoyancy) SNOSNO+

9. Scintillator Wish List high density (>0.85 g/cm 3 ) chemical compatibility with acrylic high light yield, long attenuation and scattering lengths high flash point low toxicity low cost

10. Linear Alkylbenzene

11. LAB Advantages 1 1 0 compatible with acrylic (e.g. Bicron BC-531 is 95% LAB) –“BC-531 is particularly suited for intermediate sized detectors in which the containers are fabricated with common plastic materials such as PVC and acrylics. The scintillator provides over twice the light output of mineral oil based liquids having similar plastic compatibility.” high flash point 130 °C low toxicity (pseudocumene 2 4 0) cheap, (common feedstock for LAS detergent) plant in Quebec makes 120 kton/year, producer has been very accommodating high purity

12. SNO+ Monte Carlo light yield simulations KamLAND scintillator in SNO+ 629 ± 25 pe/MeV above no acrylic711 ± 27 pe/MeV KamLAND scintillator and 50 mg/L bisMSB 826 ± 24 pe/MeV above no acrylic 878 ± 29 pe/MeV KamLAND (20% PC in dodecane, 1.52 g/L PPO) ~300 pe/MeV for 22% photocathode coverage SNO+ has 54% PMT coverage; acrylic vessel only diminishes light ouput by ~10%

13. LAB Scintillator Optimization “safe” scintillators LAB has 75% greater light yield than KamLAND scintillator

14. Light Attenuation Length Petresa LAB as received attenuation length around ~20 m @ 420 nm preliminary measurement

15. Default Scintillator Identified LAB has the smallest scattering of all scintillating solvents investigated LAB has the best acrylic compatibility of all solvents investigated density  = 0.86 g/cm 3 acceptable …default is Petresa LAB with 4 g/L PPO, wavelength shifter 10-50 mg/L bisMSB because solvent is undiluted and SNO photocathode coverage is high, expect light output (photoelectrons/MeV) ~3× KamLAND

16. Geo-Neutrinos  can we detect the antineutrinos produced by natural radioactivity in the Earth? Image by: Colin Rose, Dorling Kindersley radioactive decay of heavy elements (uranium, thorium) produces antineutrinos assay the entire Earth by looking at its “neutrino glow” e

17. Geo-Neutrino Signal terrestrial antineutrino event rates: Borexino: 10 events per year (280 tons of C 9 H 12 ) / 29 events reactor KamLAND: 29 events per year (1000 tons CH 2 ) / 480 events reactor SNO+: 64 events per year (1000 tons CH 2 ) / 87 events reactor SNO+ geo-neutrinos and reactor backgroundKamLAND geo-neutrino detection…July 28, 2005 in Nature based on Rothschild, Chen, Calaprice Geophys. Res. Lett. 25, 1083 (1998) geo- in SNO+ KamLAND

18. distance from detector [km] fraction of total flux crust: blue mantle: black total: red SNO+ geo-neutrino source integral

19. SNO+ Geo-neutrinos a good follow-up to KamLAND’s first detection  potential to really constrain the radiogenic heat flow  potential for geochemistry (separate measurement of U and Th)  simple geological configuration old, stable, thick continental crust surrounds Sudbury smaller uncertainties?

20. Toy Example – Mantle Component 70-30: the 70 component has 10% uncertainty; that’s 7/30 = 0.23 80-20: the 80 component has 5% uncertainty; that’s 4/20 = 0.20

21. leverage existing investment in SNO to get new physics for relatively low cost SNO+ is uniquely positioned to make several measurements (due to depth, geology, appropriate distance to reactors, low backgrounds) costs are: –liquid scintillator procurement –mechanics of new configuration, AV certification –fluid handling and safety systems –scintillator purification –electronics/DAQ spares or upgrades? Extension of SNO Science

22. SNO+ in 2006 SNO+ in Fall 2005 “proof of principle” –liquid scintillator identified –preliminary design to holddown the acrylic vessel need more collaborators project management scintillator purification R&D electronics/DAQ plans… full TDR by Fall 2006 –including process engineering and AV mechanics proposals to funding agencies by Fall 2006

23. SNO+ in 2007 start of capital funding construction of hold-down net access detector after D 2 O removed scintillator procurement contracts …and on to converting SNO into an operating, multi-purpose, liquid scintillator detector with unique physics capabilities

24. p + p  2 H + e + + e p + e − + p  2 H + e 2 H + p  3 He +  3 He + 3 He  4 He + 2 p 3 He + p  4 He + e + + e 3 He + 4 He  7 Be +  7 Be + e −  7 Li +  + e 7 Be + p  8 B +  7 Li + p   +  8 B  2  + e + + e p-p Solar Fusion Chain Low Energy Solar Neutrinos complete our understanding of neutrinos from the Sun pep, CNO, 7 Be CNO Cycle 12 C + p → 13 N +  13 N → 13 C + e + + e 13 C + p → 14 N +  14 N + p → 15 O +  15 O → 15 N + e + + e 15 N + p → 12 C + 

25. best-fit oscillation parameters suggest MSW occurs but we have no direct evidence of MSW –day-night effect not observed –no spectral distortion for 8 B ’s testing the vacuum-matter transition is sensitive to new physics Neutrino-Matter Interaction from Peña-Garay vacuum-matter transition plug in  m 2 = 8 × 10 −5 eV 2,  = 34° N e at the centre of the Sun → E is 1-2 MeV

26. non-standard interactions MSW is linear in G F and limits from -scattering experiments  g 2 aren’t that restrictive mass-varying neutrinos Friedland, Lunardini, Peña-Garay, hep-ph/0402266 Barger, Huber, Marfatia, hep-ph/0502196 pep solar neutrinos are at the “sweet spot” to test for new physics New Physics NC non-standard Lagrangian CHARM limit Miranda, Tórtola, Valle, hep-ph/0406280 solar density fluctuations: Guzzo, Reggiani, de Holanda, hep-ph/0302303 see also Burgess et al., hep-ph/0310366 and also Balantekin and Yuksel, PRD 68, 013006 (2003)

27. pep SNO CC/NC  m 2 = 8.0 × 10 −5 eV 2 tan 2  = 0.45 SSM pep flux: uncertainty ±1.5% known source → precision test Survival Probability Rise sensitive to new physics: non-standard interactions solar density perturbations mass-varying neutrinos CPT violation large  13 sterile neutrino admixture improves precision on  12 observing the rise confirms MSW and that we know what’s going on stat + syst + SSM errors estimated

28. these plots from the KamLAND proposal muon rate in KamLAND: 26,000 d −1 compared with SNO: 70 d −1 11 C Cosmogenic Background

29. 3600 pep/year/kton >0.8 MeV 2300 CNO/year/kton >0.8 MeV 7 Be solar neutrinos using BS05(OP) and best-fit LMA Event Rates (Oscillated) resolution with 450 photoelectrons/MeV