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 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.
Pure D 2 O Salt Data NCD Data “LETA” Salt+D 2 O 3Phase All Data SNO’s Primary Measurements: Total Flux of All Neutrinos
If neutrinos have mass: For three neutrinos: Solar, ReactorAtmospheric Using the oscillation framework: For two neutrino oscillation in a vacuum: (valid approximation in many cases) CP Violating PhaseReactor...Majorana Phases Range defined for m 12, m 23 Maki-Nakagawa-Sakata-Pontecorvo matrix (Double decay only)
SNO measurements that constrain oscillations: Average survival probability, P. Day/Night differences in survival probability Energy dependence of survival probability
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, …
Sudbury Neutrino Observatory 1700 tonnes Inner Shielding H 2 O 1000 tonnes D 2 O 5300 tonnes Outer Shield H 2 O 12 m Diameter Acrylic Vessel Support Structure for 9500 PMTs, 60% coverage Urylon Liner and Radon Seal Neutrino-Electron Scattering (ES) Charged Current (CC) Neutral Current (NC)
Phase I: Just D 2 O: neutron capture on deuterium Simple detector configuration, clean measurement Low neutron sensitivity Poor discrimination between neutrons and electrons Phase II: D 2 O + NaCl: neutron capture on Chlorine Very good neutron sensitivity Better neutron electron separation Phase III: D 2 O + 3 He Proportional Counters Good neutron sensitivity Great neutron/electron separation Three Phases of SNO: 3 NC reactions Why three phases? 1.Additional information to separate NC and CC 2.Completely different systematics, which allowed us to check for consistency. 3.Allowed us to “repeat” the measurement
Phase I (D 2 O) Phase II (D 2 O+Salt) “Beam On” “Beam Off” Advantages of (2-Phase) Low Threshold Analysis Breaking NC/CC Covariance
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.
Cherenkov light and 14 ) 43 o Charged particle, v > c/n Hollow cone of emitted photons Energy & Direction ij
NEUTRINO EVENT DISPLAYED ON SNO COMPUTER SYSTEM
Controlling and Measuring Systematic Uncertainties 1.SNO spent a large fraction of the data acquisition time calibrating- which both determined the parameters for the MC and the systematic uncertainties. 2.In most cases, measured by careful comparison of calibration data with MC at various positions, times, energies, sources 3.The 3 single phase measurements were done with assumptions that often required increasing systematic uncertainties/thresholds. 4.The LETA analysis included a major re-evaluation of all systematic uncertainties from charge pedestals, source positions, fitter response, background measurements. 5.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.
SNO Calibrations Determine detector response (optical parameters and time offsets): Dye-pumped laser and laser diffuser system. Absolute Quantum efficiency ( 16 N source in center) Neutron capture efficiency ( 252 Cf, AmBe) sources throughout volume Position, direction and energy uncertainties “Isotropy” ( 16 N and 252 Cf)
’s from 8 Li ’s from 16 N and t(p, ) 4 He 252 Cf neutrons 6.13 MeV 19.8 MeV Energy calibrated to ~1.5 % Throughout detector volume Optical calibration at 5 wavelengths with “Laserball” SNO Energy Calibrations 0.5% LETA
Background Reduction Low Energy Threshold Analysis LETA energy estimator includes both `prompt’ and `late’ light 12% more hits≈6% narrowing of resolution ~60% reduction of internal backgrounds LETA Cuts help reduce external backgrounds by ~80% Fiducial Volume β γ β High charge early in time Example : Rayleigh Scatter (it was good we fixed our pedestals…)
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
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) Low Energy Threshold Analysis Systematic Uncertainties—Energy Scale No correctionWith correction 16 N calibration source 6.13 MeV s Tested with: Independent 16 N data, n capture events, Rn `spike’ events…
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% Low Energy Threshold Analysis Systematic Uncertainties—Position Tested with: neutron captures, 8 Li, outside-signal-box s Old New
Low Energy Threshold Analysis Systematic Uncertainties—Isotropy ( 14 ) MC simulation upgrades provide biggest source of improvement Tests with muon `followers’, Am-Be source, Rn spike 14 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
PassFail FailPass FailFail PassPass N PF = 1 ( - 2 )N b N FP = ( - 1 ) 2 N b N FF = ( - 1 )( - 2 )N b N PP = 1 2 N b + N s N PMT = N PP – N s = N FP * N PF / N FF Low Energy Threshold Analysis PMT PDFs Not enough CPUs to simulate sample of events Use data instead In-time ratio Early charge probability (so fixing pedestals gave us a handle on these bkds…) `Bifurcated’ analysis
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.
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 monte carlo Kernel estimation Bifurcated analyses of backgrounds And many, many arguments! Some of which were fun… at least afterwards.
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.
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. Orebi Gann, 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