The Sudbury Neutrino Observatory

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The Sudbury Neutrino Observatory
First Results and Implications Nick Jelley
(University of Oxford) for the SNO
Collaboration October 18th, 2001 CERN
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Nuclear Fusion
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Angular Resolution
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The enemy..
bs and gs from decays in these chains interfere
with our signals at low energies
And worse, gs over 2.2 MeV cause d g ? n p
Design called for D2O lt 10-15 gm/gm U/Th
H2O lt 10-14 gm/gm U/Th Acrylic lt 10-12
gm/gm U/Th
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Sources of Activity in SNO
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Water Purification and Assay

• MnOx 224Ra, 226Ra extraction ? Purification
• ? decay products counted ? Assay of
• in electrostatic counters 224Ra,226Ra
• HTiO Th, Ra, Pb extraction ? Purification
• ? chemically stripped and ? Assay of
• counted with ?? counter 224Ra,226Ra,228Th
• Vacuum Membrane Radon removal ? Purification
• De-gassing Lucas Cells
  ? Assay of 222Rn
• Reverse Osmosis conc. collection
  ? Purification
• liquid scintillator
  ? Assay
• Ion Exchange Ultrafiltration
  ? Purification

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SNO Water Assays
Targets for D2O represent a 5 background from
dg ? np
Targets are set to reduce b-g events
reconstructing inside 6m
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A Neutrino Event
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Instrumental Backgrounds
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Instrumental Background Cuts
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External g-ray background
lt1
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How do we know this worked?
Contamination measured with independent cuts
Signal loss measured with calibration sources
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Solar Neutrino Spectrum
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Signal Extraction
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Signal Extraction Results
Data resolved into CC, ES, neutron components
with Monte Carlo pdfs of Teff, cosqsun, (R/RAV)3
With the hypothesis of no neutrino
oscillations CC 975.4 39.7
events ES 106.1 15.2 events Tail of
Neutrons 87.5 24.7 events
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Radial Distribution
Nhit ? 65 (no neutrons, no low energy
backgrounds)
Edge of AV is quite sharp. ? Events from D2O
clearly identified.
Bgnd Rise
Acceptance drop
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SNO cosq? distribution
ES strongly peaked
CC 1-1/3cosq?
Neutrons isotropic
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SNO energy spectrum from unconstrained fit
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SNO CC spectrum normalised to undistorted 8B
spectrum
No evidence for shape distortion
(Adding syst. bin by bin in quadrature give c2 of
12 for 11 D.O.F.)
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Systematic Uncertainties
N(HE g events) lt10 events (68 CL)
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Solar Neutrino Fluxes

• Absolute fluxes from constrained fit

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Flux Differences
The hypothesis that this is a downward statistical
fluctuation is ruled out at 99.96
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CC/SSM ratios for various solutions
From Bahcall, Krastev, and Smirnov hep-ph/0103179
SNO 3s ? For a Teff 6.75 MeV threshold!
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Energy Distortion in the Sterile VAC solution
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SNO Ga Cl S-K
To Active Neutrinos
To Sterile Neutrinos
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Post-SNO 2? Active Oscillation Analysis
Fogli et al. 21 June 2001
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Implications of Neutrino Oscillations
Extension of Standard Model to Include Massive
Neutrinos and Mixing
Flavour Oscillations
Probe of models for new physics

• Massive Neutrinos
• Will contribute a small component to the Missing
  Dark Matter in the Universe.

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Implications for 7Be Neutrinos

• SNO 8B rate 0.347 ? 0.029 SSM

37Cl rate 0.34 ? 0.03 SSM

• 8B contribution 76
• 7Be contribution 15
• So from SNOCl alone expect
• 7Be flux 0.3 SSM

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Fmt vs. Fe
The Standard Solar Models are correct
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Ratio of CC to ES
If ?SSM 1000 produced and ?e 340
detected Then since ?? ?? ?SSM ? ?e
CC 340 ES 340 0.154(660) 442
SNO
S-K
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Implications for Cosmology
M(ne) lt 2.8 eV (Bonn et al. - Mainz) Dm
(atmospheric n) 50 meV (assuming
oscillations) (Toshito et al. Super-K) 10-5 Dm
(solar n) 30 meV (SNO Apollonio et al.)
.05 SnMn 8.4ev
0.001 Wn 0.18
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SNOs Immediate Analysis
NC from lower analysis threshold Shape Analysis
from pure D2O data
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SNOs Immediate Future
Salt Injected 28 May 2001
Conductivity Measurements Taken During Salt
Addition
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SNOs Future Analysis
The separation of CC and NC events using the pdfs
for the mean angle between hit PMTs
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SNO Schedule

• Now- Summer 2002
• Salt data
• Summer 2002- Autumn 2002
• Pure D2O run
• January 2003 - 2005
• Neutral Current detectors
• Summer 2005
• SN-2005A

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Conclusions

• The SNO detector is working and taking beautiful
  data.
• The CC rate measured in SNO is incompatible with
  the Super-K ES rate.
• This is strong evidence (gt99.8 c.l.) for the
  appearance of m or t neutrinos from the Sun.
• Sterile and Just-So2 oscillations are excluded by
  these results at gt99.8 c.l.
• The 8B n flux from the Sun is now measured to be
  in agreement with the predictions of Standard
  Solar Models.
• Super-KT2 b decay ? 0.001 lt Wn lt 0.18

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Outlook

• These results are just the first of what SNO will
  produce.
• The conclusions listed on the preceeding slide
  are systematics dominated. They will be severely
  tested by new measurements
• NC measurements in pure D2O
• Day/night in pure D2O
• The same measurements with NaCl added
• The same measurements with the NCDs
• It will be a very exciting time!

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Solar Neutrino Problem
Solar Model, Experiments Or Neutrino Physics Wrong
?e ? ?? or ?? ?
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S. Gil, J. Heise, R. Helmer, R.J. Komar, T.
Kutter, C.W. Nally, H.S. Ng,Y. Tserkovnyak, C.E.
Waltham. University of British Columbia T.C.
Andersen, M.C. Chon, P. Jagam, J. Law, I.T.
Lawson, R. W. Ollerhead, J. J. Simpson, N. Tagg,
J.X. Wang University of Guelph   J.C. Barton,
S.Biller, R. Black, R. Boardman, M. Bowler, J.
Cameron, B. Cleveland, X. Dai, G. Doucas, J.
Dunmore, H. Fergani, A.P. Ferraris, K.Frame, H.
Heron, C. Howard, N.A. Jelley, A.B. Knox, M. Lay,
W. Locke, J. Lyon, S. Majerus, N. McCaulay, G.
McGregor, M. Moorhead, M. Omori, N.W. Tanner, R.
Taplin, M. Thorman, P. Thornewell. P.T. Trent,
D.L.Wark, N. West, J. Wilson University of
Oxford E. W. Beier, D. F. Cowen, E. D. Frank, W.
Frati, W.J. Heintzelman, P.T. Keener, J. R.
Klein, C.C.M. Kyba, D. S. McDonald, M.S.Neubauer,
F.M. Newcomer, S. Oser, V. Rusu, R. Van Berg,
R.G. Van de Water, P. Wittich. University of
Pennsylvania   Q.R. Ahmad, M.C. Browne, T.V.
Bullard, P.J. Doe, C.A. Duba, S.R. Elliott, R.
Fardon, J.V. Germani, A.A. Hamian, R. Hazama,
K.M. Heeger, M. Howe, R. Meijer Drees, J.L.
Orrell, R.G.H. Robertson, K. Schaffer, M.W.E.
Smith, T.D. Steiger, J.F. Wilkerson. University
of Washington R.G. Allen, G. Buhler, H.H.
Chen University of California, Irvine   Deceased
J. Boger, R. L Hahn, J.K. Rowley, M.
Yeh Brookhaven National Laboratory  I. Blevis,
F. Dalnoki-Veress, W. Davidson, J. Farine, D.R.
Grant, C. K. Hargrove, I. Levine, K. McFarlane,
C. Mifflin, T. Noble, V.M. Novikov, M. O'Neill,
M. Shatkay, D. Sinclair, N. Starinsky Carleton
University   J. Bigu, J.H.M. Cowan, E. D.
Hallman, R.U. Haq, J. Hewett, J.G. Hykawy, G.
Jonkmans, A. Roberge, E. Saettler, M.H.
Schwendener, H. Seifert, R. Tafirout, C. J.
Virtue. Laurentian University   Y. D. Chan, X.
Chen, M. C. P. Isaac, K. T. Lesko, A. D. Marino,
E. B. Norman, C. E. Okada, A. W. P. Poon, A. R.
Smith, A. Schülke, R. G. Stokstad. Lawrence
Berkeley National Laboratory T. J. Bowles, S.
J. Brice, M. Dragowsky, M.M. Fowler, A.
Goldschmidt, A. Hamer, A. Hime, K. Kirch, G.G.
Miller, J.B. Wilhelmy, J.M. Wouters. Los Alamos
National Laboratory E. Bonvin, M.G. Boulay, M.
Chen, F.A. Duncan, E.D. Earle, H.C. Evans, G.T.
Ewan, R.J. Ford, A.L. Hallin, P.J. Harvey, J.D.
Hepburn, C. Jillings, H.W. Lee, J.R. Leslie, H.B.
Mak, A.B. McDonald, W. McLatchie, B. Moffat, B.C.
Robertson, P. Skensved, B. Sur. Queen's
University
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n Reactions in SNO
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Signals in SNO
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The SNO Detector
1000 tonnes D2O
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
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Construction
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Signals in SNO
ES
CC
Charged-current spectrum is more sensitive to
shape distortions!
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Signals in SNO
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Signals in SNO
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Evidence for Neutrino Oscillations
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SNO Calibrations

• Electronics Calibration
• Electronic pulsers
• Optical Calibration
• Pulsed laser 2ns (337, 365, 386, 420, 500 and
  620 nm)
• ?Attenuation, Reflection, Scattering, Relative QE
• Energy Calibration
• 16N ? 6.13 MeV ?s
• p,T ? 19.8 MeV ?s
• neutrons ? 6.25 MeV ?s
• 8Li ? ? spectrum endpoint
• Low Energy Backgrounds
• Encapsulated Th and U sources

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SNO Energy Calibrations
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SNO Event Reconstruction