Solar Neutrino Observations with the Sudbury Neutrino Observatory

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Solar Neutrino Observations with The Sudbury
Neutrino Observatory
George Ewan for the SNO Collaboration Beyond the
desert June 2003
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Solar Neutrinos
Experiment Exp/SSM

• Homestake 0.33
• SAGEGALLEX/GNO 0.58
• KamiokandeSuperK 0.46
• SNO CC (June 2001) 0.35

SNO NC (April 2002) 1
SNO CC vs NC implies flavor change, which can
then explain other experimental results .
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Solar Model Independent Measurements of Neutrino
Oscillations SuperKamiokande, SNO (Using 8B
Solar Neutrinos)

• MSW Effects
• - Distortion of the spectrum
• - Regeneration in the Earth (Day/Night Effects)

• Other Time Dependent Effects
• - Seasonal effects (Earth-Sun Distance,
  Neutrino Magnetic Moments ..)
• - Long Term Solar cycle (Neutrino Magnetic
  Moments )

• Charged Current to Neutral Current comparisons
• - Electron Neutrino flux compared to Total
  Active Neutrino flux

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n Reactions in SNO

• Both SK, SNO
• Mainly sensitive to ne,, less to n? and n?
• Strong directional sensitivity

• Good measurement of ne energy spectrum
• Weak directional sensitivity ? 1-1/3cos(q)

- ne ONLY

• Measure total 8B n flux from the sun.

- Equal cross section for all n types
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Figure from Scientific American April 2003
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Solar Neutrino Physics From SNO
Flavor change/oscillations
Fcc
ne
SNO
June 2001

Fes
ne 0.154(nm nt)
SK
Fcc
ne

April 2002
SNO
Fnc
ne nm nt
April 2002
Total 8B Solar Neutrino Flux
June 2001
April 2002
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SNO Run Sequence

• Neutron Detection Method
• Capture on D
• Capture on Cl
• Capture on 3He
• Event by event separation of CC and NC events

The Three Phases

• Pure D2O
• Good CC sensitivity
• Added Salt in D2O
• Enhanced NC sensitivity
• Neutral Current Detectors
• 3He proportional counters in the D2O

Nov. 1999- May 2001
n ? d ? t ? g ? e? (Eg 6.3 MeV)
Counting Since June 2001
n ? 35Cl ? 36Cl ? ?g ? e? (E?g 8.6 MeV)
n ? 3He ? p ? t
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Sudbury Neutrino Observatory
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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Signals in SNO (Monte Carlo, Renormalized)
Pure D2O
X 0.45
X 1/3
9 NHIT/MEV
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SNO Energy Calibrations
6.13 MeV
19.8 MeV
252Cf neutrons
bs from 8Li gs from 16N and t(p,g)4He
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Signal InformationMonte Carlo Simulations

• Hits and Energy

• Direction from Sun

• Radial Response

n ? d ? t ? g ? e? (Eg 6.25 MeV)
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Radioactive Backgrounds
Sources
Consequences
Low Energy Threshold

• High Energy Rock Gammas
• Uranium Chain
• Thorium Chain
• Muon spallation products
• PMT b-g
• Instrumental Backgrounds

Fiducial Volume Cut
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Measuring U/Th Content

• Ex-situ
• Ion exchange (224Ra, 226Ra)
• Membrane Degassing (222Rn)
• Count daughter product decays

• In-situ
• Low energy data analysis
• Separate 208Tl 214Bi
• Using Event isotropy

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The data set is used for a hypothesis test of no
neutrino oscillations by assuming no MSW
distortion and comparing NC and CC. rates
PRL 89 (2002) 011306
PRL 89 (2002) 011301
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Shape Constrained Signal Extraction Results
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Uncertainties in fluxes
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Charged Current Energy Spectrum
CC spectrum normalized to predicted 8B spectrum.
? no evidence for shape distortion.
CC spectrum derived from fit without constraint
on shape of 8B spectrum above 6.75 MeV
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Solar Neutrino Flux Day/Night Asymmetries
SNO Separate Spectra For Day and Night
Day-Night Flux Asymmetry
Signal Extraction in ?e, ?totalAtotal 0 ASNOe
7.0 4.9 ASKe 5.3 3.7
Signal Extraction in ?CC, ?NC, ?ES ASNOCC
14.0 6.3 ASNONC -20.4 16.9

1.3 -1.2
1.5 -1.4

2.4 -2.5
2.0 -1.7


? SNO data consistent with MSW oscillation
interpretation
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Solar Neutrino Flux (Pure D2O)

• 8B SSM Flux (BP01)

1.01
F(nx) 5.05 x106 cm-2s-1
-0.81

• 8B SSM Flux First SNO Result (SNO SK)

• Signal extraction in R3, cosqSun, Energy
  (Constrain)

Signal extraction in R3, cosqSun only
F(nx) 6.42 (stat.) (syst.) x106
cm-2s-1
1.57
0.55
-1.57
-0.58
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log (tan2 Q) lt 0 implies m2 gt m1
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Holanda and Smirnov Phys.Rev D66 (2002) 113005
Less than Maximal Mixing at 3 s
SOLAR LMA
Best Fit Dm2 6.2 x 10 -5 eV2 tan2 q
0.40 Flux/SSM 1.06
3 s Bounds Dm2 lt 3.3 x 10-4 tan2 q lt 0.80
tan2 Q lt 1 implies m2 gt m1
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Improved SNO CC/NC and Day/Night will improve
precision
Day Night Contours ()
CC/NC Contours
Holanda, Smirnov JACP 0302 (2003) 001
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4 - Neutrino Models
LSND
2 2
If there are only 3 neutrinos then
does not work with LSND included. Therefore
4 or more n if LSND confirmed by MiniBoone
Either Atm. or Solar n flavor changes, or both,
must produce a sterile neutrino with significant
probability. (Peres and Smirnov)
)
ns
ns
(
(
)
1

ne nt ns
ne nt ns
ATM
SOL
lt 0.19 _at_ 90 (SK)
lt 0.13 _at_ 1 s
Uncertainty on solar Sterile component can be
Reduced further By future SNO and
Kamland Results.
3 1
Neither Atm. or Solar flavor changes need
produce many sterile neutrinos.
But P (nm --gt ns)LSND Um4 Ue4 2
Is strongly limited by Um4 and Ue4 upper
bounds from other experiments (reactor,
accelerator, atmos.).
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Bound on Sterile Neutrinos Solar/Kamland data
ne -gt (cos h) nx (sin h) ns
fB 8B Total Flux/SSM (BP00)
Fit to fB and h
c2 min
sin2 h 0, fB 1.00
lt 0.13 (1 s) lt 0.52 (3 s)
sin2 h
Bahcall, Gonzales-Garcia, Pena-Garay, JHEP 0302
(2003) 009
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SUMMARY OF SNO SOLAR NEUTRINO MEASUREMENTS

• SNO shows 5.3 s evidence for neutrino flavor
  change to active neutrinos.
• Result is consistent with previous SNO-SK
  comparison that gave
• 3.3 s evidence.
• MSW analysis of all experiments strongly favors
  LMA solution.
• Transformation solely to sterile neutrinos ruled
  out at more than 5 s.
• Possible Sterile component (particularly 22)
  strongly restricted by
• comparison with Kamland reactor, SK Atmospheric
  n.
• No evidence of regeneration in Earth.

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Signals in SNO (Monte Carlo, Renormalized)
Pure D2O
Plus Salt
X 0.45
X 1/3
9 NHIT/MEV
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Neutron Response
Factor of 3-4 increase in stats - larger capture
cross-section - energy response peaks higher
Pure D2O
Volume weighted efficiency 14.38 /- 0.53

• Systematics Include
• vertex reconstruction
• source position
• 252Cf source strength
• burst selection
• background
• energy scale and resolution

Salt
Total aPercent Level
Preliminary
Preliminary
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Statistical Separation of CC and NC by Pattern
Recognition of Events In Salt Data
CC
Single Electron
NC
Multiple Gammas
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Salt Phase data
Preliminary
Higher E and capture s reduces background problem
Event isotropy helps break signal covariances
Data is being analyzed with a blindness parameter
added. We are Completing the final calibrations
and will be removing the salt soon.
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Summary

• Pure D2O Phase
• Flavour Transformation
• Neutrinos Massive
• SSM working well
• Combined n Results
• g MSW Model g LMA Favoured Region
• Salt
• Increased NC statistics Additional
  Isotropy Separation
• Precision Fluxes with No Shape Constraint
• Improved CC/NC Measurement
• Day/Night and Spectral Shape
• gimproved precision in MSW space
• Next Phase NCDs in shortly
• 3He counters
• event-by-event separation

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Pure D2O
Signals in SNO (Monte Carlo, Renormalized)
Plus 3He Detectors for NC

• Phase 3
• Independent
• Signals for NC
• Capture in 3He
• Suppresses
• 6.25 MeV
• Gammas from
• Capture on D

9 NHIT/MEV
NHIT will be lower by 15
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New International Underground Science Facility At
the Sudbury site SNOLAB

• To build on the underground science being done
• by SNO and pursue further measurements of
• Neutrinos from Astrophysical sources
• A next generation SNO experiment (Wavelength
  Shifter ?)
• Lower Energy Solar Neutrinos
• Other Forms of Dark Matter (WIMPS)
• PICASSO (Bubble Detectors)
• Double Beta Decay
• Low Background Counting Test Facility

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The New SNOLAB
NEW 14m x 14m x 60m, Clean Area
SNO
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The SNO Collaboration
S. Gil, J. Heise, R.L. Helmer, R.J. Komar, T.
Kutter, C.W. Nally, H.S. Ng, Y.I. Tserkovnyak,
C.E. Waltham University of British Columbia J.
Boger, R.L. Hahn, J.K. Rowley, M. Yeh Brookhaven
National Laboratory R.C. Allen, G. Bühler, H.H.
Chen University of California at Irvine I.
Blevis, F. Dalnoki-Veress, J. Farine, D.R. Grant,
C.K. Hargrove, I. Levine, K. McFarlane, H. Mes,
C. Mifflin, A.J. Noble, V.M. Novikov, M. O'Neill,
M. Shatkay, D. Sinclair, N. Starinsky Carleton
University G. Milton, B. Sur Chalk River
Laboratories T.C. Andersen, K. Cameron, M.C.
Chon, P. Jagam, J. Karn, J. Law, I.T.
Lawson, R.W. Ollerhead, J.J. Simpson, N.
Tagg, J.-X. Wang University of Guelph J. Bigu,
J.H.M. Cowan, E.D. Hallman, R.U. Haq, J. Hewett,
J.G. Hykawy, G. Jonkmans, S. Luoma, A. Roberge,
E. Saettler, M.H. Schwendener, H. Seifert, R.
Tafirout, C.J. Virtue Laurentian University Y.D.
Chan, X. Chen, K.T. Lesko, A.D. Marino, E.B.
Norman, C.E. Okada, A.W.P. Poon, A. Schuelke,
A.R. Smith, R.G. Stokstad Lawrence Berkeley
National Lab T.J. Bowles, S.J. Brice, M.R.
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
J.D. Anglin, M. Bercovitch, W.F. Davidson, R.S.
Storey National Research Council of Canada J.C.
Barton, S. Biller, R.A. Black, R.J. Boardman,
M.G. Bowler, J. Cameron, B. Cleveland, X. Dai,
G. Doucas, J. Dunmore, H. Fergani, A.P. Ferraris,
K. Frame, H. Heron, N.A. Jelley, A.B. Knox, M.
Lay, W. Locke, J. Lyon, S. Majerus, N.
McCauley, G. McGregor, M. Moorhead, M. Omori,
N.W. Tanner, R.K. Taplin, P. Thornewell, M.
Thorman, 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.M.
Oser, V.L. Rusu, R.G. Van de Water, R. Van Berg,
P. Wittich University of Pennsylvania R. Kouzes,
M.M. Lowry Princeton University E.Bonvin, M.G.
Boulay, Y. Dai, M. Chen, E.T.H. Clifford, , F.A.
Duncan, E.D. Earle,H.C. Evans, G.T. Ewan, R.J.
Ford, A.L. Hallin, P.J. Harvey, R. Heaton, J.D.
Hepburn, C. Jillings, H.W. Lee, J.R. Leslie, H.B.
Mak, A.B. MacDonald, W. McLatchie, B.A. Moffat,
B.C. Robertson, T.J. Radcliffe, P.
Skensved Queen's University Q.R. Ahmad, M.C.
Browne, T.V. Bullard, T.H. Burritt, G.A. Cox,
P.J. Doe,C.A. Duba, S.R. Elliott, J.V. Germani,
A.A. Hamian, R. Hazama, K.M. Heeger, M. Howe, R.
MeijerDrees, J.L. Orrell, R.G.H.
Robertson,K.K. Schaffer, M.W.E. Smith, T.D.
Steiger, J.F. Wilkerson University of Washington
Deceased
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SNO Data Taking Phases
Phase II (dissolved salt)
Phase III (3He n counters)
Phase I (pure D2O)
n ? 3He ? p ? t
Neutron capture on Cl
Neutron capture on D
Multiple g s, 8.6 MeV
Single 6.25 MeV g
Statistical separation (Energy, radius)
Statistical separation (Isotropy)
Independent channel
NC uncorrelated to CC
High CC-NC correlation
Better CC-NC separation
Future
Present
Past
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Constraints on Sterile Neutrinos

• If oscillation with mixing solely to a sterile
  neutrino is occurring the SNO CC - derived 8B
  flux above a threshold of 6.75 MeV will be
  essentially identical with the integrated
  Super-Kamiokande ES - derived 8B flux above a
  threshold of 8.6 MeV.
• ? Correcting for the ES threshold the flux
  difference is
• 0.53 0.17, or 3.1 ?
• ? Therefore the hypothesis of oscillations
  solely to sterile neutrinos is excluded at the
  3.1 ? level.

• Oscillations to a combination of active and
  sterile neutrinos are still allowed.
• A partial flux of sterile neutrinos would not be
  observed by ES, CC or NC.
• Such a partial sterile component is restricted
  by the agreement between
• the extracted 8B flux (assuming active
  neutrinos) and the calculated SSM flux.
• 
  
  (lt 35)
• ( Also see Barger et al hep-ph/0106207, Bahcall
  et al hep-ph/0204194)

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Neutrino Reactions in SNO


?

n
CC
e-
p
p
d
e

• Q 1.445 MeV
• good measurement of ne energy spectrum
• some directional info ? (1 1/3 cosq)
• ne only

• Q 2.22 MeV
• measures total 8B n flux from the Sun
• equal cross section for all n types

?

e-
n
e-
n
ES
x
x

• low statistics
• mainly sensitive to ne, some n? and n?
• strong directional sensitivity

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Example 10 On CC/NC
Holanda and Smirnov JACP 0302
) 001
SNO
CC/NC Contours