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Solar Neutrino Physics from SNO

Solar Neutrino Physics from SNO. Aksel Hallin SNOLAB Opening May 14, 2012. SNO physics: measure neutrinos that directly probe fusion reactions in the core of the sun. SNO sensitivity. Science in 1990:: Bahcall’s plot, neutrino oscillations.

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Solar Neutrino Physics from SNO

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  1. Solar Neutrino Physics from SNO Aksel Hallin SNOLAB Opening May 14, 2012

  2. SNO physics: measure neutrinos that directly probe fusion reactions in the core of the sun SNO sensitivity

  3. Science in 1990:: Bahcall’s plot, neutrino oscillations SNO made a direct measurement of the total flux of solar neutrinos. Without SNO, we have the standard solar model predictions but no model independent measurement of the total solar neutrino flux. Other experiments made measurements of electron neutrinos, and saw the significant depletion noted here, but were unable to distinguish between effects from an incorrect solar model and effects due to neutrino oscillations. Ray Davis and John Bahcall had observed neutrino oscillations in the 70’s; but it was a model dependent observation that was suggestive but not definitive.

  4. SNO’s Primary Measurements: Total Flux of All Neutrinos 3Phase All Data “LETA” Salt+D2O NCD Data Salt Data Pure D2O

  5. If neutrinos have mass: Using the oscillation framework: For three neutrinos: Maki-Nakagawa-Sakata-Pontecorvo matrix (Double b decay only) Solar, Reactor Atmospheric CP Violating Phase Reactor... Majorana Phases Range defined for Dm12, Dm23 For two neutrino oscillation in a vacuum: (valid approximation in many cases)

  6. SNO measurements that constrain oscillations: • Average survival probability, P. • Day/Night differences in survival probability • Energy dependence of survival probability

  7. SNO’s measurement and neutrino oscillation parameters: SNO D2O (2001) SNO 3 phase (2012)

  8. Approximate Daya Bay Result 0.0235 +/- 0.0045

  9. Some of the other SNO Measurements PRD80 021001(2009): Muon Paper Measured 1229 days, 514 event, 1.22+/- 0.09 Bartol flux prediction Periodicity Paper: PRD72, 052010 (2005) No variations between 1d and 10 years Except for eccentricity of orbit Hep neutrino measurementPreliminary fit to all SNO data. Consistent with SSM 8e3/cm**2/s +Nucleon decay, antineutrinos, spallation neutrons, …

  10. Neutral Current (NC) Sudbury Neutrino Observatory Neutrino-Electron Scattering (ES) 1000 tonnes D2O Charged Current (CC) Support Structure for 9500 PMTs, 60% coverage 12 m Diameter Acrylic Vessel 1700 tonnes Inner Shielding H2O 5300 tonnes Outer Shield H2O Urylon Liner and Radon Seal

  11. Three Phases of SNO: 3 NC reactions • Phase I: Just D2O: neutron capture on deuterium • Simple detector configuration, clean measurement • Low neutron sensitivity • Poor discrimination between neutrons and electrons • Phase II: D2O + NaCl: neutron capture on Chlorine • Very good neutron sensitivity • Better neutron electron separation • Phase III: D2O + 3He Proportional Counters • Good neutron sensitivity • Great neutron/electron separation Why three phases? Additional information to separate NC and CC Completely different systematics, which allowed us to check for consistency. Allowed us to “repeat” the measurement

  12. Advantages of (2-Phase) Low Threshold Analysis • Breaking NC/CC Covariance Phase I (D2O) “Beam Off” Phase II (D2O+Salt) “Beam On”

  13. Observables Photomultiplier tube • position • time • Charge Neutrons Alphas NCD digitized data:

  14. Reconstruction Reconstructed event • Vertex position • Electron direction • energy • Isotropy (reaction discriminator) • particle identification and counting in NCD’s History of SNO saw a continuous progression of fitters- to improve resolution, Incorporate shadowing of the NCD’s, better incorporation of correlations, etc.

  15. qij Energy & Direction b14 = b1 + 4b4 Cherenkov light and b14 Charged particle, v > c/n Hollow cone of emitted photons 43o )

  16. NEUTRINO EVENT DISPLAYED ON SNO COMPUTER SYSTEM

  17. Controlling and Measuring Systematic Uncertainties SNO spent a large fraction of the data acquisition time calibrating- which both determined the parameters for the MC and the systematic uncertainties. In most cases, measured by careful comparison of calibration data with MC at various positions, times, energies, sources The 3 single phase measurements were done with assumptions that often required increasing systematic uncertainties/thresholds. The LETA analysis included a major re-evaluation of all systematic uncertainties from charge pedestals, source positions, fitter response, background measurements. The 3Phase analysis included all the data, but used a high PMT –side energy threshold to stay away from backgrounds. It did include correlations between systematic effects in the various phases.

  18. SNO Calibrations • Determine detector response (optical parameters and time offsets): Dye-pumped laser and laser diffuser system. • Absolute Quantum efficiency (16N source in center) • Neutron capture efficiency (252Cf, AmBe) sources throughout volume • Position, direction and energy uncertainties • “Isotropy” (16N and 252Cf)

  19. SNO Energy Calibrations 6.13 MeV 19.8 MeV 0.5% LETA Energy calibrated to ~1.5 % Throughout detector volume 252Cf neutrons b’s from 8Li g’s from 16N and t(p, g)4He Optical calibration at 5 wavelengths with “Laserball”

  20. Low Energy Threshold Analysis • Background Reduction LETA energy estimator includes both `prompt’ and `late’ light Rayleigh Scatter 12% more hits≈6% narrowing of resolution ~60% reduction of internal backgrounds Fiducial Volume LETA Cuts help reduce external backgrounds by ~80% γ β Example: β High charge early in time (it was good we fixed our pedestals…)

  21. Low Energy Threshold Analysis • Systematic Uncertainties • Nearly all systematic uncertainties from calibration data-MC • Upgrades to MC simulation yielded many reductions • Residual offsets used as corrections w/ add`l uncertainties • All uncertainties verified with multiple calibration sources

  22. Low Energy Threshold Analysis • Systematic Uncertainties—Energy Scale No correction With correction 16N calibration source 6.13 MeVgs Volume-weighted uncertainties: Old: Phase I = ±1.2% Phase II = ±1.1% New: Phase I = ±0.6% Phase II = ±0.5% (about half Phase-correlated) Tested with: Independent 16N data, n capture events, Rn `spike’ events…

  23. Low Energy Threshold Analysis • Systematic Uncertainties—Position Old New Central runs remove source positioning offsets, MC upgrades reduce shifts Fiducial volume uncertainties: Old: Phase I ~ ±3% Phase II ~ ±3% New: Phase I ~ ±1% Phase II ~ ±0.6% Tested with: neutron captures, 8Li, outside-signal-box ns

  24. Low Energy Threshold Analysis • Systematic Uncertainties—Isotropy (b14) MC simulation upgrades provide biggest source of improvement Tests with muon `followers’, Am-Be source, Rn spike b14 Scale uncertainties: Old: Phase I --- , Phase II = ±0.85% electrons, ±0.48% neutrons New: Phase I ±0.42%, Phase II =±0.24% electrons, +0.38%-0.22% neutrons

  25. Low Energy Threshold Analysis • PMT b-gPDFs Not enough CPUs to simulate sample of events Use data instead PassFail Early charge probability Early charge probability PassPass FailFail FailPass In-time ratio In-time ratio `Bifurcated’ analysis NPF= e1(1-e2)Nb NFP = (1-e1) e2Nb NFF = (1-e1)(1-e2)Nb NPP = e1e2Nb + Ns NPMT= NPP – Ns = NFP * NPF / NFF (so fixing pedestals gave us a handle on these bkds…)

  26. Pulse Shape Analysis in NCDs (3 Phase) 1115 ± 79 neutrons

  27. Signal Extraction: a multiparameter fit of the data to pdf’s describing the various signals and backgrounds; including correlations between phases, and a variety of systematic parameters. In 3 phase analysis, almost 60 parameters.

  28. Three Phase Fit

  29. Analysis techniques used by SNO • Blind analysis • Independent analyses (at least two for every publication) • Extended ML minimization against Monte Carlo and analytic pdf’s of varying dimensionality. • Parameterizing and floating systematic functions • Markov chain montecarlo • Kernel estimation • Bifurcated analyses of backgrounds And many, many arguments! Some of which were fun… at least afterwards.

  30. SNO has published it’s final solar neutrino analyses. A handful of remaining papers, such as the hep paper, the antineutrino paper and neutron backgrounds from cosmic rays atSNO depth will be finalized soon.

  31. People of SNO B. Aharmim, Q.R. Ahmad, S.N. Ahmed, R.C. Allen, T.C. Andersen, J.D. Anglin, A.E. Anthony, N. Barros, J.C. Barton, E.W. Beier, A. Bellerive, B. Beltran, M. Bercovitch, M. Bergevin, J. Bigu, S.D. Biller, R.A. Black, I. Blevis, R.J. Boardman, J. Boger, E. Bonvin, K. Boudjemline, M.G. Boulay, M.G. Bowler, T.J. Bowles, S.J. Brice, M.C. Browne, G. Buehler, T.V. Bullard, T.H. Burritt, B. Cai, K. Cameron, J. Cameron, Y.D. Chan, D. Chauhan, M. Chen, H.H. Chen, X. Chen, M.C. Chon, B.T. Cleveland, E.T.H. Clifford, J.H.M. Cowan, D.F. Cowen, G.A. Cox, Y. Dai, X. Dai, F. Dalnoki-Veress, W.F. Davidson, H. Deng, J. Detwiler, M. DiMarco, P.J. Doe, G. Doucas, M.R. Dragowsky, P.-L. Drouin, C.A. Duba, F.A. Duncan, M. Dunford, J. Dunmore, E.D. Earle, S.R. Elliott, H.C. Evans, G.T. Ewan, J. Farine, H. Fergani, A.P. Ferraris, F. Fleurot, R.J. Ford, J.A. Formaggio, M.M. Fowler, K. Frame, E.D. Frank, W. Frati, N. Gagnon, J.V. Germani, S. Gil, A. Goldschmidt, J.TM. Goon, K. Graham, D.R. Grant, E. Guillian, S. Habib, R.L. Hahn, A.L. Hallin, E.D. Hallman, A. Hamer, A.A. Hamian, R.U. Haq, C.K. Hargrove, P.J. Harvey, R. Hazama, R. Heaton, K.M. Heeger, W.J. Heintzelman, J. Heise, R.L. Helmer, J.D. Hepburn, H. Heron, J. Hewett, A. Hime, C. Howard, M.A. Howe, M. Huang, J.G. Hykawy, M.C.P. Isaac, P. Jagam, B. Jamieson, N.A. Jelley, C. Jillings, G. Jonkmans, J. Karn, P.T. Keener, K.J. Keeter, K. Kirch, J.R. Klein, A.B. Knox, R.J. Komar, L.L. Kormos, M. Kos, R. Kouzes, C. Kraus, C.B. Krauss, T. Kutter, C.C.M. Kyba, J. Law, I.T. Lawson, M. Lay, H.W. Lee, K.T. Lesko, J.R. Leslie, I. Levine, J.C. Loach, W. Locke, M.M. Lowry, S. Luoma, J. Lyon, R. MacLellan, S. Majerus, H.B. Mak, J. Maneira, A.D. Marino, R. Martin, N. McCauley, A.B. McDonald, D.S. McDonald, K. McFarlane, S. McGee, G. McGregor, W. McLatchie, R. Meijer Drees, H. Mes, C. Mifflin, G.G. Miller, M.L. Miller, G. Milton, B.A. Moffat, B. Monreal, J. Monroe, M. Moorhead, B. Morissette, C.W. Nally, M.S. Neubauer, F.M. Newcomer, H.S. Ng, B.G. Nickel, A.J. Noble, A.J. Noble y, E.B. Norman, V.M. Novikov, N.S. Oblath, C.E. Okada, H.M. O'Keeffe, R.W. Ollerhead, M. Omori, M. O'Neill, G.D. OrebiGann, J.L. Orrell, S.M. Oser, R.A. Ott, S.J.M. Peeters, A.W.P. Poon, G. Prior, T.J. Radcliffe, S.D. Reitzner, K. Rielage, A. Roberge, B.C. Robertson, R.G.H. Robertson, J.K. Rowley, V.L. Rusu, E. Saettler, K.K. Schaer, A. Schuelke, M.H. Schwendener, J.A. Secrest, S.R. Seibert, H. Seifert, M. Shatkay, O. Simard, J.J. Simpson, D. Sinclair, P. Skensved, A.R. Smith, M.W.E. Smith, T.J. Sonley, N. Starinsky, T.D. Steiger, R.G. Stokstad, L.C. Stonehill, R.S. Storey, B. Sur, R. Tafirout, N. Tagg, N.W. Tanner, R.K. Taplin, G. Tešic, M. Thorman, P. Thornewell P.T. Trent, N. Tolich, Y.I. Tserkovnyak, T. Tsui, C.D. Tunnell, R. Van Berg, R.G. Van de Water, B.A. VanDevender, C.J. Virtue, B.L. Wall, D. Waller, C.E. Waltham, H. Wan Chan Tseung, J.-X. Wang, D.L. Wark, N. West, J.B. Wilhelmy, J.F. Wilkerson, J. Wilson, J.R. Wilson, P. Wittich, J.M. Wouters, A. Wright, M. Yeh, M. Yeh, F. Zhang, K. Zuber

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