The Sudbury Neutrino Observatory
First Results and Implications
Nick Jelley (University of Oxford)for the SNO Collaboration
October 18th, 2001
CERN
2
Nuclear Fusion
pep 2H + e
pp 2H + e+ +e
2H + p 3He + 3He + 3He 4He + 2p
3He + 4He 7Be +e + 7Be 7Li +e7Li + p 2 4Hep + 7Be 8B +8B 8Be* + e+ +e8Be* 2 4He
3
Angular Resolution
4
The enemy…..s and s from decays in these chains interfere with our signals at low energies
And worse, s over 2.2 MeVcause d + n + p
Design called for: D2O < 10-15 gm/gm U/Th H2O < 10-14 gm/gm U/Th Acrylic < 10-12 gm/gm U/Th
5
Sources of Activity in SNO
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Water Purification and AssayMnOx 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 PurificationDe-gassing Lucas Cells Assay of
222Rn
Reverse Osmosis conc. collection Purification liquid scintillator Assay
Ion Exchange & Ultrafiltration Purification
7
SNO Water Assays
Targets for D2O represent a 5%background from d+n+p
Targets are set to reduce - events reconstructing inside 6m
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A Neutrino Event
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Instrumental BackgroundsNote Neck Tubes Fired
Electronic Pickup
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Instrumental Background Cuts
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External -ray background
r3
u•r <1%
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How do we know this worked?
Signal loss measured withcalibration sources
Contamination measured with independent cuts
Fraction of hits in a prompt time windowM
ean
angl
e be
twee
n ph
otot
ube
hits
Number of phototubes hit
Frac
tion
of g
ood
even
ts c
ut
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Solar Neutrino Spectrum
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Signal Extraction
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Signal Extraction ResultsData resolved into CC, ES, neutron components with Monte Carlo pdfs of Teff, cossun, (R/RAV)3 With the hypothesis of no neutrino oscillations
CC 975.4 ± 39.7 eventsES 106.1 ± 15.2 events
Tail of Neutrons 87.5 ± 24.7 events
240.9 live-days between 11/99-1/01
No statistically significant differences between Blind and Open data sets (75 days/166 days)
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Radial Distribution
Fiducial Volume Cut at 550 cm
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 cos distribution
Electron Angle with respect to the direction from the Sun
ES: strongly peakedCC: 1-1/3cosNeutrons: isotropic
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SNO energy spectrum from unconstrained fit
Data points derived by fitting each energy bin independently
Monte Carlo ofundistorted 8Bspectrum normalizedto the data
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SNO CC spectrum normalised to undistorted 8B spectrum
Ratio to BP2001:0.347 ± 0.029
(Adding syst. bin by bin in quadrature give 2 of ~12 for 11 D.O.F.)
No evidence forshape distortion
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Systematic UncertaintiesSource CC (%) ES (%)Energy scale +6.1, -5.2 +5.4, -3.5Energy resolution 0.5 0.3Energy scale non-linearity 0.5 0.4Vertex accuracy 3.1 3.3Vertex resolution 0.7 0.4Angular resolution 0.5 2.2High energy +0, -0.8 +0, -1.9Low energy background 0.0 –0.2 0.0 –0.2Instrumental background +0.0, -0.2 +0.0, -0.5Trigger efficiency 0.0 0.0Live Time 0.1 0.1Cut acceptance +0.7, -0.6 +0.7, -0.6Earth orbit eccentricity 0.2 0.217O, 18O 0.0 0.0Experimental uncertainty +7.0, -6.2 +6.8, -5.7Cross section 3.0 3.0Solar model +20, -16 +20, -16
80
60
40
20
0
141210864Energy (MeV)
N(HE events): <10 events (68% CL)
21
Solar Neutrino “Fluxes” Absolute fluxes from constrained fit:
CC (8B) = 1.75 ± 0.07 ± 0.05 (stat) (sys.) (theory)ES (8B) = 2.39 ± 0.34 (stat) (sys.)
+0.12- 0.11
+0.16- 0.14
SNO:
SNO:
+0.08- 0.07ES (8B) = 2.32 ± 0.03
(stat) (sys.)
Super-K*
*S. Fukuda, et al., hep-ex/0103032
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“Flux” Differences
• CC at SNO vs ES at SK
ES - CC = 0.57 ± 0.17 3.35 effectSK SNO
The hypothesis that this is a downwardstatistical fluctuation is ruled out at 99.96%
• CC at SNO vs ES at SNO
ES - CC = 0.64 ± 0.40 1.6 effect SK SNO
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CC/SSM ratios for various solutions
From Bahcall, Krastev, and Smirnov; hep-ph/0103179
SNO 3 For a Teff = 6.75 MeV threshold!
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Energy Distortion in the Sterile VAC solution
Sterile VAC predictslarge energy distortion
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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
Massive Neutrinos:
• Will contribute a small component to the Missing Dark Matter in the Universe.
Extension of Standard Model to Include Massive Neutrinos and Mixing
=e
Uml
Flavour Oscillations:
Probe of models for new physics
28
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 SNO+Cl alone expect 7Be flux ~ 0.3 SSM
29
vs. e
+1.01- 0.81SSM (8B) = 5.05 106 cm-2s-1
The StandardSolar Modelsare correct
SNO (8B) = 5.44 ±0.99 106 cm-2s-1 +SK
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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
)(14.0ESCC
e
e
0.154
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Implications for Cosmology
M(e) < 2.8 eV (Bonn et al. - Mainz)
m (atmospheric ) ~ 50 meV (assuming oscillations)(Toshito et al. Super-K)
~10-5 ≤ m (solar ) ≤ ~30 meV (SNO + Apollonio et al.)
0.001 ≤ ≤ 0.18
.05 ≤ ≤ 8.4ev
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SNO’s Immediate AnalysisNC from lower analysis threshold Shape Analysis from pure D2O data
Seasonal and other Exotica
hep-neutrino analysis
Day/Night analysis
Muons
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SNO’s Immediate Future
NC Salt (BP98)
Conductivity Measurements Taken During Salt Addition
Salt Injected28 May 2001
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SNO’s Future Analysis
The separation of CCand NC events usingthe pdfs for the mean angle betweenhit PMTs
35
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 (>99.8% c.l.) for the
appearance of or neutrinos from the Sun. Sterile and Just-So2 oscillations are excluded by
these results at >99.8% c.l. The 8B flux from the Sun is now measured to be
in agreement with the predictions of Standard Solar Models.
+Super-K+T2 decay 0.001 < < 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 Problem1968 Homestake 600 tonnes C2Cl4
e + 37Cl 37Ar+ e 1989 Kamiokande 2000 tonnes H2O e + e e + e 1990 Sage 1992 Gallex 90 tonnes Gae + 71Ga 71Ge+ e 1998 Super-K 30000 tonnes H2O e + e e + e
Solar Model, ExperimentsOr Neutrino Physics Wronge or ?
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J. Boger, R. L Hahn, J.K. Rowley, M. YehBrookhaven 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
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
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Reactions in SNO
-Good measurement of e energy spectrum-Weak directional sensitivity 1-1/3cos()- e only.
CC -eppd e
-Measure total 8B flux from the sun.- Equal cross section for all types
NCxx npd
ES -- eνeν x x
-Low Statistics -All n types but enhanced sensitivity to e
-Strong directional sensitivity
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Signals in SNO
NC Salt (BP98)
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The SNO Detector
1700 tonnes InnerShielding H2O
1000 tonnes D2O
5300 tonnes Outer Shield H2O
12 m Diameter Acrylic Vessel
Support Structure for 9500 PMTs, 60% coverage
Urylon Liner andRadon Seal
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Construction
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Signals in SNO
Charged-current spectrumis more sensitive to shape
distortions!
ES
CC
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Signals in SNO
e
e
NCCCCharged-Current to Neutral Current
ratio is a direct signature for oscillations
0
0.2
0.4
0.6
0.8
1
1.2
1.4
0.8
No oscillations
MSW oscillations
SNO’s Anticipated CC/NC Sensitivity
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Signals in SNO
)(14.0ESCC
e
e
CC/ES Could also show
significant effects! 0.154
Bahcall et al.
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Evidence for Neutrino Oscillations
3.3
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SNO CalibrationsElectronics Calibration
Electronic pulsersOptical 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 BackgroundsEncapsulated Th and U sources
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SNO Energy Calibrations
’s from 8Li ’s from 16N and t(p,)4He
252Cf neutrons
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SNO Event Reconstruction
Reconstruction position of 8Li events
Reconstruction Resolution