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 Predicted Energy Spectra of Solar Neutrinos from the Standard Solar Model (SSM) LENS Arrows Denote Experimental Thresholds Brookhaven Science Associates U.S. Department of Energy 71Ga 37Cl SNO+ Super-K, SNO Water >40 Years of Neutrino R&D @ BNL Chemistry Dep’t. • Done: HOMESTAKE Radiochemical Detector C2Cl4; 37Cl + ne 37Ar + e- (~40 years) • Done: GALLEX Radiochemical Detector Ga; 71Ga + ne 71Ge + e- (1986 - 1998) • Now: SNO Water Čerenkov Real-time Detector Note: Hahn became Leader of BNL Group in 1986: GALLEX, SNO, 13 Ultra-pure D2O (1996 - 2006) • New : #1 Focus for the Future THETA-13 High-Precision Experiments at Daya Bay Nuclear Reactors Real-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&D began 2002) • New: SNOLab, SNO+ (R&D) with LS (began 2005) BNL’s Ray Davis and His Discoveries 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+. h Brookhaven Science Associates U.S. Department of Energy Solar Neutrino Problem-”Disappearance” SOLAR FUSION: 4p 4He + 2e+ + 2ne + 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”). Matter Enhanced n Oscillations MSW gives a dramatic extension of oscillation sensitivity to potential regions in Dm2 Solar n data are consistent with the MSW hypothesis. LMA 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 SAGE & GALLEX Kamiokande Homestake 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 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 One million pieces transported down in the 10 foot square mine cage and re-assembled under ultra-clean conditions. Sensitive to 8B n Unique Feature: ‘Appearance’ of nx vs. ‘Disappearance’ of ne Brookhaven Science Associates U.S. Department of Energy SNO – used 3 neutron detection methods ( 3 “different detectors” with possibly different systematics) Phase I (D2O) Phase II (salt) Phase III (3He) Nov. 99 - May 01 July 01 - Sep. 03 Summer 04 - Dec. 06 Published Published 2 t NaCl. n captures on 35Cl(n, g)36Cl s = 44 b Observe multiple g’s PMT array readout Enhanced NC In Progress 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 35Cl+n 2H+n 6.25 MeV 5 cm 8.6 MeV Several g rays One g ray n 3H p 3He 3H 36Cl n + 3He p + 3H Signals in SNO (Monte Carlo, Renormalized) Pure D2O Plus Salt X 0.45 X 1/3 NC Salt (BP98) Phase 1, D2O: 2002 NC Results Phase 2, NaCl: Improved NC Signal, 2003 Results ~ 9 NHIT/MEV SNO Energy Calibrations 6.13 MeV 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 NEUTRINO EVENT DISPLAYED ON SNO COMPUTER SYSTEM Chemistry in SNO • Purify the water with respect to radioactivity and nonradioactive 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. 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+gn+p Measure U/Th Backgrounds in D2O Salt Phase Several g’s in U and Th chains will photodisintegrate deuteron • In-situ: – Low energy data via Tl & Bi isotropy • Ex-situ: – Ion exchange (224Ra, 226Ra) – Membrane degassing – Count daughter product decays Radon Calibration Radial distributions for SNO Salt Data 0 550 600 (Reconstructed radius, cm/ 600)3 700 cm Sun-angle distributions for SNO Salt Data n points: Toward sun Away from sun Energy Spectra Extracted from Salt Data Without 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 Spectral Shapes are Extracted from the Salt Data, Not Assumed to Fit 8B Shape Difference in CC Flux Between Unconstrained and 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 8B-Shape Brookhaven Science Associates U.S. Department of Energy SNO SOLVED THE SOLAR NEUTRINO PROBLEM SNO RESULTS, Salt + D2O 391 live days SNO Results from Pure D2O Results from Other Exp’ts. SNO CC Result agrees with Davis’ Cl value. Measuring Neutrino Oscillation Parameters, Narrowing the Available Phase Space Solar Neutrinos Solar Neutrinos + KamLAND 2003 (ne rate) Agreement between oscillation parameters for n and n Solar Neutrinos + KamLAND 2004 (ne rate+spectrum) ‘Discovery Era in Neutrino Physics Is Finished, Entering Precision Era’ 13 value UNKNOWN. From CHOOZ, only have limit, < 11° WHY SO SMALL? Want to measure with 1% precision. Dm232 =2.410-3 eV2 23 45 Atmospheric n (Super-K) nm nt Dm221 =7.8 10-5 eV2 12 =32 H2O Accelerator n (K2K) ne nm,t LS D2O Solar n (SNO) Reactor n (KamLAND) • Neutrinos oscillate, must have mass • Evidence for neutrino flavor conversion ne • SNO Solved Solar Neutrino Problem nm nt 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 nx Detection Principle 2H + nx p + n + nx - 2.22 MeV 3He (NC) PMT + n p + 3H + 0.76 MeV 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 n Neutron Capture in the NCDs ~ 1200 n captures per year from solar n n+ 3He p+ 3H (Q = 764 keV) 3H 3 573 keV H 764 keV p p-t track fully contained in gas hits wall p hits wall p anode wire NCD wall 3 H 191 keV End view of an NCD with representative ionization tracks Idealized energy spectrum in a 3He proportional counter. The main peak corresponds to the 764keV Q-value of the 3He(n, p)3H reaction. NCD Energy Spectrum Energy spectrum from one deployed NCD string with an Am-Be neutron source. 191-keV shoulder from proton going into the wall 764-keV peak 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 THE FUTURE OF SNO SNO finished Phase I, with Pure D 2O, 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 n from pep and CNO solar branches; see Borexino, LENS… Want to see transition from matter-dominated to vacuum oscillations. Brookhaven Science Associates U.S. Department of Energy SNOLAB 14m x 14m x 60m, Clean Area THE END Thank you for your attention.