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

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

Done:HOMESTAKEDone: HOMESTAKE Radiochemical Detector C 2 Cl 4 ; 37 Cl + e  37 Ar + e - (~40 years) Done: GALLEXDone: GALLEX Radiochemical Detector Ga; 71 Ga + e  71 Ge + e - ( ) Now: SNONow: SNO Water Čerenkov Real-time Detector Ultra-pure D 2 O (  2006) New : #1 Focus for the Future THETA-13New : #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: LENSNew: LENS Real-time Detector (R&D) 115 In-LS (began 2000), Detect pp and 7 Be Solar Neutrinos New: Very Long-Baseline Neutrino OscillationsNew: Very Long-Baseline Neutrino Oscillations Neutrino Beam from Accelerator (R&D began 2002) New: SNOLab, SNO+New: SNOLab, SNO+ (R&D) with LS (began 2005) >40 Years of Neutrino BNL Chemistry Dep’t. Note: Hahn became Leader of BNL Group in 1986: GALLEX, SNO,  13

h Brookhaven Science Associates U.S. Department of Energy 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+.  Ray Davis died May 31, 2006, at age 91+.

Solar Neutrino Problem-”Disappearance” 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”). SOLAR FUSION: 4p  4 He + 2e e + 26 MeV

Matter Enhanced Oscillations LMA LOW SMA MSW gives a dramatic extension of oscillation sensitivity to potential regions in  m 2 Solar data are consistent with the MSW hypothesis. But prior to SNO, only had circumstantial evidence from Cl, Ga, Kamiokande, S-K; i.e., we knew the  e disappeared. Needed definitive proof: * Appearance measurement * Independent of SSM

Enter The SNO Collaboration 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 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

Sudbury Neutrino Observatory, SNO 1700 tonnes Inner Shielding H 2 O 1000 tonnes D 2 O 5300 tonnes Outer Shield H 2 O 12 m Diameter Acrylic Vessel 5-cm thick walls Support Structure for 9500 PMTs, 60% coverage Urylon Liner and Radon Seal REALTIMEREALTIME

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

Brookhaven Science Associates U.S. Department of Energy Unique Feature: ‘Appearance’ of x vs. ‘Disappearance’ of e Sensitive to 8 B

Phase II (salt) July 01 - Sep. 03 Published Phase III ( 3 He) Summer 04 - Dec. 06 In Progress Phase I (D 2 O) Nov May 01 Published SNO – used 3 neutron detection methods (  3 “different detectors” with possibly different systematics) n captures on 2 H(n,  ) 3 H  = b Observe 6.25 MeV  PMT array readout Good CC 36 proportional counters 3 He(n, p) 3 H  = 5330 b Observe p and 3 H PMT-independent readout, event by event 2 t NaCl. n captures on 35 Cl(n,  ) 36 Cl  = 44 b Observe multiple  ’s PMT array readout Enhanced NC 36 Cl 35 Cl+n 8.6 MeV 3H3H 2 H+n 6.25 MeV n + 3 He  p + 3 H p 3H3H 5 cm n 3 He One  ray Several  rays

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

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

NEUTRINO EVENT DISPLAYED ON SNO COMPUTER SYSTEM

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 D 2 O inventory and ratio of H 2 O/ D 2 O.

An important enemy, 232 Th Decay Chain…..  s and  s interfere with our signals at low energies  ’s over 2.2 MeV from 208 Tl  d +  n + p Require 232 Th content < 3.7 x g/g in D 2 O

Measure U/Th Backgrounds in D 2 O In-situ: –Low energy data via Tl & Bi isotropy Ex-situ: –Ion exchange ( 224 Ra, 226 Ra) –Membrane degassing –Count daughter product decays Salt Phase Several  ’s in U and Th chains will photodisintegrate deuteron Radon Calibration

Radial distributions for SNO Salt Data (Reconstructed radius, cm/ 600) cm

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

Energy Spectra Extracted from Salt Data Without Imposing known 8 B Shape Electron kinetic energy Flux Values (Updated 2006) (10 6 cm -2 s -1 ) CC : 1.68(10) ES : 2.35(27) NC : 4.94(43)

Brookhaven Science Associates U.S. Department of Energy Spectral Shapes are Extracted from the Salt Data, Not Assumed to Fit 8 B Shape  Difference in CC Flux Between Unconstrained and 8 B-Shape Constraint = 0.11  0.05(stat) (syst) (units are 10 6 cm -2 s -1 )  Consistent with Hypothesis of No Spectral Distortion   CC /  NC =  (stat)  (syst)   -e /  total  1/3,  - ,  /  total  2/3  Result is independent of the solar model  Results from Salt Phase, LMA Is Favored   m 2 = 7.1 X ev 2,  12 = 32.5 o

SNO Results from Pure D2O SNO RESULTS, Salt + D 2 O 391 live days SNO SOLVED THE SOLAR NEUTRINO PROBLEM SNO CC Result agrees with Davis’ Cl value. Results from Other Exp’ts.

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

‘Discovery Era in Neutrino Physics Is Finished, Entering Precision Era’ Solar (SNO)    e  ,  Atmospheric (Super-K) Reactor (KamLAND) Accelerator (K2K) Neutrinos oscillate, must have mass Evidence for neutrino flavor conversion e   SNO Solved Solar Neutrino Problem H2OH2O D2OD2O LS  m 2 21 =7.8  eV 2  12 =32   m 2 32 =2.4  eV 2  23  45   13 value UNKNOWN. From CHOOZ, only have limit, < 11° WHY SO SMALL? Want to measure with 1% precision.

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. Detection Principle 2 H + x  p + n + x MeV (NC) 3 He + n  p + 3 H MeV x n 40 Strings on 1-m grid 440 m total active length NCD PMT SNO Phase III (NCD Phase)- Began 2004, To Finish End of 2006  3 He Proportional Counters (“NC Detectors”)

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

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

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  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  = 

Brookhaven Science Associates U.S. Department of Energy THE FUTURE OF SNO  SNO finished Phase I, with Pure D 2 O, and Phase II, with NaCl + D 2 O; now running NCDs for ~2 years.  Will end beginning of January  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 D 2 O, 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.

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

THE END Thank you for your attention.