1. SNO+: SNO with Liquid Scintillator SNOLAB Workshop IV August 15, 2005 Mark Chen Queen’s University

2. Outline brief review of the science technical progress project issues –SNOLAB infrastructure –funding –collaboration –schedule

3. 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

4. complete our understanding of neutrinos from the Sun pep, CNO, 7 Be explore the neutrino-matter interaction which is sensitive to new physics 3 rd recommendation of the APS Neutrino Study Low Energy Solar Neutrinos

5. 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 transition from matter to vacuum dominance…tests the neutrino- matter interaction 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

6. 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 Guzzo, Reggiani, de Holanda, hep-ph/0302303 see also Burgess et al., hep-ph/0310366

7. 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

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

9. SNO+ pep SNOLAB is the only deep site that exists where the pep solar neutrinos could be measured with precision. pep solar neutrinos are a known source – enables a precision measurement (this is not the case with 7 Be). pp solar neutrinos are more difficult and may not reveal as much as pep (pp survival probability set by the average vacuum P ee ). First observation of the CNO solar neutrino would be important for astrophysics.

10. Real KamLAND Backgrounds external pep window

11. radiopurity requirements – 40 K, 210 Bi (Rn daughter) – 85 Kr, 210 Po (seen in KamLAND) not a problem since pep signal is at higher energy than 7 Be –U, Th not a problem if one can repeat KamLAND scintillator purity – 14 C not a problem since pep signal is at higher energy pep Solar Backgrounds

12. 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

13. Earth’s Heat Flow  models of Earth’s heat sources suggest that radioactivity contributes 40-100% towards Earth’s total heat flow the radiogenic portion is not that well known! geophysicists want to understand Earth’s thermal history H.N. Pollack, S.J. Hurter and J.R. Johnson, Reviews of Geophysics 31(3), 267-280, 1993

14. 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 the above plot is for Borexino…geo/reactor ratio at Sudbury would be twice as high KamLAND geo-neutrino detection…great start! Rothschild, Chen, Calaprice (1998)

15. Fundamental Geophysics  SNO+ geo-neutrinos: a good follow-up to KamLAND’s first detection potential to really constrain the radiogenic heat flow potential to really constrain the radiogenic heat flow potential for geochemistry (U and Th separation) potential for geochemistry (U and Th separation) tests models of Earth’s chemical origin tests models of Earth’s chemical origin

16. 1 kton organic liquid scintillator would maintain excellent supernova neutrino capability – e + p[large rate] – e + 12 C (CC) – e + 13 C (CC) [2.2 MeV threshold, 1.1% abundance] – x NC excitation of 12 C (NC) – x + p elastic scattering (NC) [large rate] see Beacom et al., PRD 66, 033001(2002) Supernova Neutrinos

17. SNO plus liquid scintillator plus double beta isotopes: SNO++ add  isotopes to liquid scintillator –dissolved Xe gas (2%) –organometallic chemical loading (Nd, Se, Te) –dispersion of nanoparticles (Nd 2 O 3, TeO 2 ) enormous quantities (high statistics) and low backgrounds help compensate for the poor energy resolution of liquid scintillator possibly source in–source out capability Double Beta Decay: SNO++

18. 150 Nd 3.37 MeV endpoint (9.7 ± 0.7 ± 1.0) × 10 18 yr 2  half-life measured by NEMO-III isotopic abundance 5.6% 1% natural Nd-loaded liquid scintillator in SNO++ has 560 kg of 150 Nd compared to 37 g in NEMO-III cost: $1/g for metallic Nd; cheaper as Nd salt…on the web NdCl 3 sold in lot sizes of 100 kg, 1 ton, 10 tons table from F. Avignone Neutrino 2004

19. 2  Background good energy resolution needed but whopping statistics helps compensate for poor resolution and… turns this into an endpoint shape distortion measure rather than a peak search

20. 0 : 1000 events per year with 1% natural Nd-loaded liquid scintillator in SNO++ Test = 0.150 eV maximum likelihood statistical test of the shape to extract 0 and 2 components…~240 units of  2 significance after only 1 year! Klapdor-Kleingrothaus et al., Phys. Lett. B 586, 198, (2004) simulation: one year of data by Alex Wright

21. Nd-carboxylate in Pseudocumene made by Yeh, Garnov, Hahn at BNL window with >6 m light attenuation length {

22. external 241 Am  Compton edge 137 Cs 207 Bi conversion electrons Nd Scintillator Works!

23. new physics for relatively low cost lower energy solar neutrinos: the best (and only) game in town to test the neutrino-matter interaction SNO+ is uniquely positioned to make these measurements (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? Extending SNO Science

24. SNO+ Technical  liquid scintillator selection and design  AV engineering  cover gas, fluid handling, safety  scintillator purification  electronics/DAQ (spares, upgrade…) to be tackled next year

25. AV Hold-down  Bob Brewer working on design SNO had rope basket support for the AV in an old design (+10% density difference D 2 O- H 2 O) SNO had rope basket support for the AV in an old design (+10% density difference D 2 O- H 2 O) believes optimization of above design can hold down 15% buoyancy (scintillator density  = 0.85) believes optimization of above design can hold down 15% buoyancy (scintillator density  = 0.85)

26. Scintillator Design  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

28. LAB Advantages compatible with acrylic (e.g. Bicron BC-531 ) –“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, supplier has been very accommodating high purity 1 1 0

29. LAB Process

30. Petresa Plant – Bécancour, QC

31. Scintillating SNO Monte Carlo Alex Wright’s implementation and calculations PC+1.5 g/L PPO with KamLAND yield 629 ± 25 pe/MeV above no acrylic711 ± 27 pe/MeV PC+1.5 g/L PPO 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%

32. Light Yield “safe” scintillators high density LAB has 75% greater light yield than KamLAND scintillator Vladimir Novikov’s studies and results

33. Light Attenuation Length Petresa LAB as received ~10 m preliminary measurement

34. 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 acceptable …default is Petresa LAB with 4 g/L PPO, wavelength shifter 10-50 mg/L bisMSB for unloaded scintillator physics…light output (photoelectrons/MeV) more than 3× KamLAND

35. Still Need to Check for LAB compatibility with stressed acrylic long term stability accurately measure long attenuation lengths – for Monte Carlo input accurately measure mean scattering length – for Monte Carlo input fluorescence timing, quantum yields alpha-beta PSD (not critical, but useful)

36. Answers to LOI Questions what are the ultimate sensitivity limits for a neutrinoless double beta decay search? –this is important to investigate and we are eager to explore the potential; as the double beta decay option is a lower priority “bonus”, we have focused on developing other aspects of the project first

37. More LOI Questions existing SNO utility drift adequate for scintillator purification? power requirements? –above two questions: scintillator purification being examined and no anomalously large demands foreseen for the above items, though not yet known estimate access needs during installation? –in progress (AV mechanics, process fluids and cover gas) space and power demands change for double beta? –not foreseen to be different

38. LOI Questions cont’d what are the main challenges for scintillator purification (beyond KamLAND and Borexino)? –SNO+ pep has fewer backgrounds than Borexino and KamLAND due to higher energy ( 85 Kr, 210 Po, alphas no longer problems) – 210 Bi and 40 K stand out as “new” backgrounds more critical for SNO+ than for the others 210 Bi benefits from KamLAND 210 Pb reduction investigations 40 K will be targeted in 2006 SNO+ scintillator purification research need space for these activities? –above ground…spike tests at Laurentian or Queen’s

39. LOI Questions: Safety plans to ensure safe handling and containment –being developed…“safe” scintillator candidate LAB is favourable in this regard

40. LOI Questions: Funding and Establish Collaboration possible funding sources: NSERC, CFI, US DOE, new European collaborators actively trying to recruit collaborators current numbers: –Queen’s15 –Laurentian2 –SNOLAB4 –BNL3 –LANL1+ –LIP Lisbon1+ –TU Munich5 potential –potential interest from collaborators in Italy, Russia

41. SNO+ is an NSERC-funded R&D project goal is proof of principle by Fall 2005 –AV hold-down engineering solution demonstrated –liquid scintillator mixture selected/designed with demonstrated compatibility with acrylic and suitable optical properties –fluid handling and safety underground discussed –scientific motivation fully developed for proposal –ballpark project cost estimates inclusion in Canada’s IPP-NSERC long range plan Near Term Project Schedule

42. SNO+ in 2006 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

43. 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