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Results (and Expectations) from SNO, the Sudbury Neutrino Observatory

Results (and Expectations) from SNO, the Sudbury Neutrino Observatory. Richard L. Hahn. Solar-Neutrino & Nuclear-Chemistry Group * Chemistry Department, BNL. PRC-US Workshop Beijing, June 2006. * Research sponsored by the Office of Nuclear Physics,

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Results (and Expectations) from SNO, the Sudbury Neutrino Observatory

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  1. Results (and Expectations) from SNO, the Sudbury Neutrino Observatory Richard L. Hahn Solar-Neutrino & Nuclear-Chemistry Group * Chemistry Department, BNL PRC-US Workshop Beijing, June 2006 *Research sponsored by the Office of Nuclear Physics, Office of Science, U.S. Department of Energy

  2. Predicted Energy Spectra of Solar Neutrinos from the Standard Solar Model (SSM) Super-K, SNO LENS  71Ga  37Cl Water   SNO+ Arrows  Denote Experimental Thresholds Brookhaven Science AssociatesU.S. Department of Energy

  3. >40 Years of Neutrino R&D @ BNL Chemistry Dep’t. • Done:HOMESTAKERadiochemical Detector • C2Cl4; 37Cl + ne 37Ar+ e- (~40 years) • Done: GALLEX Radiochemical Detector • Ga;71Ga + ne 71Ge + e- (1986 - 1998) • Now:SNO Water ČerenkovReal-timeDetector • Ultra-pure D2O(1996 -  2006) • New : #1 Focus for the FutureTHETA-13 High-PrecisionExperiments at Daya Bay Nuclear ReactorsReal-time Detector (R&D) • Gd in Liquid Scintillator, Gd-LS(began 2004) • New: LENS Real-time Detector(R&D) • 115In-LS(began 2000),Detect pp and 7Be Solar Neutrinos • New: Very Long-Baseline Neutrino Oscillations • Neutrino Beam from Accelerator (R&Dbegan 2002) • New:SNOLab, SNO+ (R&D) with LS(began 2005) Note: Hahn became Leader of BNL Group in 1986: GALLEX, SNO, 13

  4. BNL’s Ray Davis and His Discoveries h • He was the first to observe neutrinos from the Sun. • This was a very significant result, confirming our ideas of how stars produce energy. • This was the basis of his 2002 Nobel Physics Prize. • But, in a sense, we scientists expected that result. • More exciting for us, he observed an unexpected result, too few neutrinos compared to the SSM. • This anomaly became known as the Solar Neutrino Problem, and led to several important experiments; some were done by the BNL Solar-Neutrino Group. • Ray Davis died May 31, 2006, at age 91+. Brookhaven Science AssociatesU.S. Department of Energy

  5. Solar Neutrino Problem-”Disappearance” SOLAR FUSION: 4p 4He + 2e++ 2e + 26 MeV PRE-SNO: Either Solar Models are Incomplete and/or Incorrect, e.g., temperature of core is lower than expected, Or Neutrinos undergo Flavor Changing Oscillations (or other “New Physics”).

  6. Matter Enhanced n Oscillations MSW gives a dramatic extension of oscillation sensitivity to potential regions in Dm2 LMA Solar n data are consistent with the MSW hypothesis. SMA • But prior to SNO, only had circumstantial evidence from Cl, Ga, Kamiokande, S-K; i.e., • we knew the ne disappeared. • Needed definitive proof: * Appearance measurement * Independent of SSM LOW

  7. Enter The SNO Collaboration T. Kutter, C.W. Nally, S.M. Oser, C.E. Waltham University of British Columbia J. Boger, R.L. Hahn, R. Lange, M. Yeh Brookhaven National Laboratory A.Bellerive, X. Dai, F. Dalnoki-Veress, R.S. Dosanjh, D.R. Grant, C.K. Hargrove, R.J. Hemingway, I. Levine, C. Mifflin, E. Rollin, O. Simard, D. Sinclair, N. Starinsky, G. Tesic, D. Waller Carleton University P. Jagam, H. Labranche, J. Law, I.T. Lawson, B.G. Nickel, R.W. Ollerhead, J.J. Simpson University of Guelph J. Farine, F. Fleurot, E.D. Hallman, S. Luoma, M.H. Schwendener, R. Tafirout, C.J. Virtue Laurentian University Y.D. Chan, X. Chen, K.M. Heeger, K.T. Lesko, A.D. Marino, E.B. Norman, C.E. Okada, A.W.P. Poon, S.S.E. Rosendahl, R.G. Stokstad Lawrence Berkeley National Laboratory M.G. Boulay, T.J. Bowles, S.J. Brice, M.R. Dragowsky, S.R. Elliott, M.M. Fowler, A.S. Hamer, J. Heise, A. Hime, G.G. Miller, R.G. Van de Water, J.B. Wilhelmy, J.M. Wouters Los Alamos National Laboratory S.D. Biller, M.G. Bowler, B.T. Cleveland, G. Doucas, J.A. Dunmore, H. Fergani, K. Frame, N.A. Jelley, S. Majerus, G. McGregor, S.J.M. Peeters, C.J. Sims, M. Thorman, H. Wan Chan Tseung, N. West, J.R. Wilson, K. Zuber Oxford University E.W. Beier, M. Dunford, W.J. Heintzelman, C.C.M. Kyba, N. McCauley, V.L. Rusu, R. Van Berg University of Pennsylvania S.N. Ahmed, M. Chen, F.A. Duncan, E.D. Earle, B.G. Fulsom, H.C. Evans, G.T. Ewan, K. Graham, A.L. Hallin, W.B. Handler, P.J. Harvey, M.S. Kos, A.V. Krumins, J.R. Leslie, R. MacLellan, H.B. Mak, J. Maneira, A.B. McDonald, B.A. Moffat, A.J. Noble, C.V. Ouellet, B.C. Robertson, P. Skensved, M. Thomas, Y.Takeuchi Queen’s University D.L. Wark Rutherford Laboratory and University of Sussex R.L. Helmer TRIUMF A.E. Anthony, J.C. Hall, J.R. Klein University of Texas at Austin T.V. Bullard, G.A. Cox, P.J. Doe, C.A. Duba, J.A. Formaggio, N. Gagnon, R. Hazama, M.A. Howe, S. McGee, K.K.S. Miknaitis, N.S. Oblath, J.L. Orrell, R.G.H. Robertson, M.W.E. Smith, L.C. Stonehill, B.L. Wall, J.F. Wilkerson University of Washington

  8. Sudbury Neutrino Observatory, SNO 1000 tonnes D2O R E A L T I M E 12 m Diameter Acrylic Vessel 5-cm thick walls Support Structure for 9500 PMTs, 60% coverage 1700 tonnes Inner Shielding H2O 5300 tonnes Outer Shield H2O Urylon Liner and Radon Seal

  9. One million pieces transported down in the 10 foot square mine cage and re-assembled under ultra-clean conditions.

  10. Sensitive to 8B n Unique Feature: ‘Appearance’ of nx vs. ‘Disappearance’ of ne Brookhaven Science AssociatesU.S. Department of Energy

  11. 35Cl+n 5 cm 2H+n 8.6 MeV 6.25 MeV n 3H p 3He 3H n + 3He  p + 3H 36Cl SNO – used 3 neutron detection methods( 3 “different detectors” with possibly different systematics) Phase I (D2O) Nov. 99 - May 01 Published Phase II (salt) July 01 - Sep. 03 Published Phase III (3He) Summer 04 - Dec. 06 In Progress 2 t NaCl. n captures on 35Cl(n, g)36Cl s = 44 b Observe multiple g’s PMT array readout Enhanced NC 36 proportional counters 3He(n, p)3H s = 5330 b Observe p and 3H PMT-independent readout, event by event n captures on 2H(n, g)3H s = 0.0005 b Observe 6.25 MeV g PMT array readout Good CC Several g rays One g ray

  12. Signals in SNO (Monte Carlo, Renormalized) NC Salt (BP98) Phase 1, D2O: 2002 NC Results Phase 2, NaCl: Improved NC Signal, 2003 Results Plus Salt Pure D2O X 0.45 X 1/3 ~ 9 NHIT/MEV

  13. 6.13 MeV SNO Energy Calibrations 19.8 MeV 252Cf neutrons n d  t g …  e (Eg = 6.3 MeV) b’s from 8Li g’s from 16N and t(p,g)4He

  14. NEUTRINO EVENT DISPLAYED ON SNO COMPUTER SYSTEM

  15. Chemistry in SNO • Purify the water with respect to radioactivity and non-radioactive chemical impurities. • Ion Exchange & Ultrafiltration, MnOx, HTiO, Vacuum & Membrane De-gassing, Reverse Osmosis. • Assay the water for residual contamination: Need to sample 100’s of tonnes in time period short compared to radioactive decay under study to reach sensitivity. • Optical clarity. • Biological Growth. • Add or remove salt (Phase II). • Maintain stability of water system: temperature, pressure,... • Control D2O inventory and ratio of H2O/ D2O.

  16. An important enemy, 232Th Decay Chain….. Require 232Th content < 3.7 x 10-15 g/g in D2O bs and gs interfere with our signals at low energies g’s over 2.2 MeV from 208Tl d + g  n + p

  17. Radon Calibration Salt Phase Measure U/Th Backgrounds in D2O Several g’s in U and Th chains will photodisintegrate deuteron • In-situ: • Low energy datavia Tl & Bi isotropy • Ex-situ: • Ion exchange(224Ra, 226Ra) • Membrane degassing • Count daughter product decays

  18. Radial distributions for SNO Salt Data 550 600 700 cm 0 (Reconstructed radius, cm/ 600)3

  19. Sun-angle distributions for SNO Salt Data n points: Away from sun Toward sun

  20. Energy Spectra Extracted from Salt DataWithout Imposing known 8B Shape Flux Values (Updated 2006) (106 cm-2 s-1) nCC: 1.68(10) nES: 2.35(27) nNC: 4.94(43) Electron kinetic energy

  21. Spectral Shapes are Extracted from the Salt Data, Not Assumed to Fit 8B Shape • Difference in CC Flux Between Unconstrained and 8B-Shape Constraint = 0.11  0.05(stat) +0.06 -0.09(syst) (units are 106 cm-2 s-1) • Consistent with Hypothesis of No Spectral Distortion • CC/ NC= 0.306  0.026 (stat)  0.024 (syst) • n-e/ total  1/3,n-m,t/ total  2/3 • Result is independent of the solar model • Results from Salt Phase, LMA Is Favored • Dm2 = 7.1 X 10-5 ev2, 12 = 32.5o Brookhaven Science AssociatesU.S. Department of Energy

  22. SNO SOLVED THE SOLAR NEUTRINO PROBLEM SNO RESULTS, Salt + D2O391 live days SNO Results from Pure D2O Results from Other Exp’ts. SNO CC Result agrees with Davis’ Cl value.

  23. Solar Neutrinos + KamLAND 2003 (e rate) Solar Neutrinos + KamLAND 2004 (e rate+spectrum) Agreement between oscillation parameters for  and  Measuring Neutrino Oscillation Parameters,Narrowing the Available Phase Space Solar Neutrinos

  24. ‘Discovery Era in Neutrino Physics Is Finished,Entering Precision Era’ • • Neutrinos oscillate, must have mass • • Evidence for neutrino flavor conversion e   • SNO Solved Solar Neutrino Problem 13valueUNKNOWN. From CHOOZ, only have limit, < 11° WHY SO SMALL? Want to measure with 1% precision. H2O m232 =2.410-3 eV2 23  45 Accelerator  (K2K) Atmospheric (Super-K)   m221 =7.8 10-5 eV2 12 =32 e , LS D2O Reactor  (KamLAND) Solar  (SNO)

  25. x n SNO Phase III (NCD Phase)- Began 2004, To Finish End of 2006 • 3He Proportional Counters (“NC Detectors”) 40 Strings on 1-m grid 440 m total active length Detection Principle 2H + x p + n + x - 2.22 MeV (NC) 3He + n  p + 3H + 0.76 MeV PMT Physics Motivation Event-by-event separation. Measure NC and CC in separate data streams. Different systematic uncertainties than neutron capture on NaCl. NCD array removes neutrons from CC, calibrates remainder. CC spectral shape. NCD

  26. Neutron Capture in the NCDs ~ 1200 n captures per year from solar n n + 3He  p + 3H (Q = 764 keV) p-t track fully contained in gas 3H hits wall p hits wall Idealized energy spectrum in a 3He proportional counter. The main peak corresponds to the 764-keV Q-value of the 3He(n, p)3H reaction. End view of an NCD with representative ionization tracks

  27. NCD Energy Spectrum 764-keV peak Energy spectrum from one deployed NCD string with an Am-Be neutron source. 191-keV shoulder from proton going into the wall

  28. Other Recent Work from SNO • Are analyzing NCD data (blind analysis) • Are analyzing data on atmospheric muons and neutrinos • Set new limit on hep flux, to be released very soon • SNO is involved in SNEWS • Published Periodicity Analysis of SNO data - Did unbinned log likelihood analysis - No unknown solar period seen - Ruled out at 3.6 s level the positive claim by Sturrock et al. from their Super-K data analysis - Only variation that was seen was due to eccentricity of Earth’s orbit, measured e = 0.0143  0.0086

  29. THE FUTURE OF SNO • SNO finished Phase I, with Pure D2O, and Phase II, with NaCl + D2O; now running NCDs for ~2 years. • Will end beginning of January 2007. • All analyses done blind. • New UG facility, “SNO Lab” is funded, being built. • Are planning a relatively low-cost new experiment, “SNO+”, to use the existing SNO acrylic vessel, DAQ, and infrastructure; remove the D2O, refill with LS. • Goal of SNO+ is to detect low-energy solar from pep and CNO solar branches; see Borexino, LENS… • Want to see transition from matter-dominated to vacuum oscillations. Brookhaven Science AssociatesU.S. Department of Energy

  30. SNOLAB 14m x 14m x 60m, Clean Area

  31. THE END Thank you for your attention.

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