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

8

A Neutrino Event

9

Instrumental BackgroundsNote Neck Tubes Fired

Electronic Pickup

10

Instrumental Background Cuts

11

External -ray background

r3

u•r <1%

12

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

13

Solar Neutrino Spectrum

14

Signal Extraction

15

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)

16

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

17

SNO cos distribution

Electron Angle with respect to the direction from the Sun

ES: strongly peakedCC: 1-1/3cosNeutrons: isotropic

18

SNO energy spectrum from unconstrained fit

Data points derived by fitting each energy bin independently

Monte Carlo ofundistorted 8Bspectrum normalizedto the data

19

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

20

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

22

“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

23

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

26

Post-SNO 2 Active Oscillation Analysis

Fogli et al. 21 June 2001

27

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

30

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

31

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

33

SNO’s Immediate Future

NC Salt (BP98)

Conductivity Measurements Taken During Salt Addition

Salt Injected28 May 2001

34

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

36

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

37

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!

38

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 ?

39

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

40

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

41

Signals in SNO

NC Salt (BP98)

42

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

44

Signals in SNO

Charged-current spectrumis more sensitive to shape

distortions!

ES

CC

45

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

46

Signals in SNO

)(14.0ESCC

e

e

CC/ES Could also show

significant effects! 0.154

Bahcall et al.

47

Evidence for Neutrino Oscillations

3.3

48

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

49

SNO Energy Calibrations

’s from 8Li ’s from 16N and t(p,)4He

252Cf neutrons

50

SNO Event Reconstruction

Reconstruction position of 8Li events

Reconstruction Resolution