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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. - PowerPoint PPT Presentation
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Solar Neutrino Physics from SNO
Aksel HallinSNOLAB 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 oscillationsSNO 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 D2OSalt Data
NCD Data “LETA” Salt+D2O
3PhaseAll Data
SNO’s Primary Measurements: Total Flux of All Neutrinos
ijijijij
ii
i
τττ
μμμ
eee
li
sandcwhere
ee
cs
sc
iδecssccs
sc
UUUUUUUUU
U
sin,cos
0000001
0010
0
00010001
00
001
10000
2/
2/
1313
1313
2323
23231212
1212
321
321
321
3
2
ilil U If neutrinos have mass:
)ELΔm.(θ)νP(ν eμ
222 271sin2sin
For three neutrinos:
Solar, Reactor Atmospheric
Using the oscillation framework:
For two neutrino oscillation in a vacuum: (valid approximation in many cases)
CP Violating Phase Reactor... Majorana Phases
Range defined for Dm12, Dm23
Maki-Nakagawa-Sakata-Pontecorvo matrix
(Double b decay only)
SNO measurements that constrain oscillations:
• Average survival probability, P.• Day/Night differences in survival probability• Energy dependence of survival probability
SNO 3 phase (2012)SNO D2O (2001)
SNO’s measurement and neutrino oscillation parameters:
ApproximateDaya Bay Result0.0235 +/- 0.0045
Some of the other SNO Measurements
PRD80 021001(2009): Muon PaperMeasured 1229 days, 514 event, 1.22+/- 0.09 Bartol flux prediction
Periodicity Paper: PRD72, 052010 (2005)No variations between 1d and 10 yearsExcept for eccentricity of orbit
Hep neutrino measurementPreliminary fit to allSNO data. Consistent withSSM 8e3/cm**2/s
+Nucleon decay, antineutrinos, spallation neutrons, …
Sudbury Neutrino Observatory
1700 tonnes Inner
Shielding H2O
1000 tonnes D2O
5300 tonnes Outer
Shield H2O
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 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
Three Phases of SNO: 3 NC reactions
Why three phases?
1. Additional information to separate NC and CC2. Completely different systematics, which allowed us to
check for consistency.3. Allowed us to “repeat” the measurement
Phase I (D2O)
Phase II(D2O+Salt)
“Beam On”
“Beam Off”
Advantages of (2-Phase) Low Threshold Analysis Breaking NC/CC Covariance
Observables
-position-time-Charge
Photomultiplier tube
NCD digitized data:
Neutrons
Alphas
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 b14
) 43o
Charged particle, v > c/n
Hollow cone of emitted photons
Energy & Direction
ij
b14 b1 4b4
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 (16N source in center)• Neutron capture efficiency (252Cf, AmBe) sources
throughout volume• Position, direction and energy uncertainties• “Isotropy” (16N and 252Cf)
b’s from 8Li g’s from 16N and t(p, g)4He
252Cf neutrons
6.13 MeV19.8 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
βγβ
High charge early in timeExample:
Rayleigh Scatter
(it was good we fixed our pedestals…)
Low Energy Threshold AnalysisSystematic 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 AnalysisSystematic Uncertainties—Energy Scale
No correction With correction
16N calibration source6.13 MeV gs
Tested with: Independent 16N 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 AnalysisSystematic Uncertainties—Position
Tested with: neutron captures, 8Li, outside-signal-box s
Old New
Low Energy Threshold AnalysisSystematic Uncertainties—Isotropy (b14)
MC simulation upgrades provide biggest source of improvementTests with muon `followers’, Am-Be source, Rn spikeb14 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
NPF = e1(1-e2)Nb
NFP = (1-e1) e2Nb
NFF = (1-e1)(1-e2)Nb
NPP = e1e2Nb + Ns
NPMT= NPP – Ns = NFP * NPF /
NFF
Low Energy Threshold AnalysisPMT bg PDFs
Not enough CPUs to simulate sample of events Use data instead
In-time ratio In-time ratio
Early
cha
rge
prob
abili
ty
Early
cha
rge
prob
abili
ty
(so fixing pedestals gave us a handle on these bkds…)
`Bifurcated’ analysis
Pulse Shape Analysis in NCDs (3 Phase)
1115 ± 79 neutrons
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.
Three Phase Fit
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 SNOB. 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
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