Results (and Expectations) from SNO,
the Sudbury Neutrino Observatory
Richard L. Hahn
Solar-Neutrino & Nuclear-Chemistry Group *
Chemistry Department, BNL
PRC-US Workshop
Beijing, June 2006
*Research sponsored by the Office of Nuclear Physics,
Office of Science, U.S. Department of Energy
Predicted Energy Spectra of Solar Neutrinos
from the Standard Solar Model (SSM)
LENS

Arrows 
Denote
Experimental
Thresholds
Brookhaven Science Associates
U.S. Department of Energy
71Ga

37Cl

SNO+

Super-K, SNO
Water
>40 Years of Neutrino R&D @ BNL Chemistry Dep’t.
• Done: HOMESTAKE Radiochemical Detector
C2Cl4; 37Cl + ne  37Ar + e- (~40 years)
• Done: GALLEX Radiochemical Detector
Ga; 71Ga + ne  71Ge + e- (1986 - 1998)
• Now: SNO Water Čerenkov Real-time Detector
Note: Hahn became Leader of BNL
Group in 1986: GALLEX, SNO, 13
Ultra-pure D2O (1996 -  2006)
• New : #1 Focus for the Future THETA-13 High-Precision Experiments
at Daya Bay Nuclear Reactors Real-time Detector (R&D)
Gd in Liquid Scintillator, Gd-LS (began 2004)
• New: LENS Real-time Detector (R&D)
115In-LS (began 2000), Detect pp and 7Be Solar Neutrinos
• New: Very Long-Baseline Neutrino Oscillations
Neutrino Beam from Accelerator (R&D began 2002)
• New: SNOLab, SNO+ (R&D) with LS (began 2005)
BNL’s Ray Davis and His Discoveries
 He was the first to observe neutrinos from the Sun.
 This was a very significant result, confirming
our ideas of how stars produce energy.
 This was the basis of his 2002 Nobel Physics Prize.
 But, in a sense, we scientists expected that result.
 More exciting for us, he observed an unexpected
result, too few neutrinos compared to the SSM.
 This anomaly became known as the Solar Neutrino
Problem, and led to several important experiments;
some were done by the BNL Solar-Neutrino Group.
 Ray Davis died May 31, 2006, at age 91+.
h
Brookhaven Science Associates
U.S. Department of Energy
Solar Neutrino Problem-”Disappearance”
SOLAR FUSION: 4p 4He + 2e+ + 2ne + 26 MeV
PRE-SNO:
Either
Solar Models are Incomplete
and/or Incorrect, e.g., temperature
of core is lower than expected,
Or
Neutrinos undergo Flavor
Changing Oscillations
(or other “New Physics”).
Matter Enhanced n Oscillations
MSW gives a dramatic
extension of oscillation
sensitivity to potential
regions in Dm2
Solar n data are consistent
with the MSW hypothesis.
LMA
SMA
But prior to SNO, only had
circumstantial evidence from
Cl, Ga, Kamiokande, S-K; i.e.,
we knew the ne disappeared.
• Needed definitive proof:
* Appearance measurement
* Independent of SSM
LOW
SAGE & GALLEX
Kamiokande
Homestake
Enter The SNO Collaboration
T. Kutter, C.W. Nally, S.M. Oser, C.E. Waltham
University of British Columbia
J. Boger, R.L. Hahn, R. Lange, M. Yeh
Brookhaven National Laboratory
A.Bellerive, X. Dai, F. Dalnoki-Veress, R.S. Dosanjh, D.R. Grant,
C.K. Hargrove, R.J. Hemingway, I. Levine, C. Mifflin, E. Rollin,
O. Simard, D. Sinclair, N. Starinsky, G. Tesic, D. Waller
Carleton University
P. Jagam, H. Labranche, J. Law, I.T. Lawson, B.G. Nickel,
R.W. Ollerhead, J.J. Simpson
University of Guelph
J. Farine, F. Fleurot, E.D. Hallman, S. Luoma,
M.H. Schwendener, R. Tafirout, C.J. Virtue
Laurentian University
Y.D. Chan, X. Chen, K.M. Heeger, K.T. Lesko, A.D. Marino,
E.B. Norman, C.E. Okada, A.W.P. Poon,
S.S.E. Rosendahl, R.G. Stokstad
Lawrence Berkeley National Laboratory
M.G. Boulay, T.J. Bowles, S.J. Brice, M.R. Dragowsky,
S.R. Elliott, M.M. Fowler, A.S. Hamer, J. Heise, A. Hime,
G.G. Miller, R.G. Van de Water, J.B. Wilhelmy, J.M. Wouters
Los Alamos National Laboratory
S.D. Biller, M.G. Bowler, B.T. Cleveland, G. Doucas,
J.A. Dunmore, H. Fergani, K. Frame, N.A. Jelley, S. Majerus,
G. McGregor, S.J.M. Peeters, C.J. Sims, M. Thorman,
H. Wan Chan Tseung, N. West, J.R. Wilson, K. Zuber
Oxford University
E.W. Beier, M. Dunford, W.J. Heintzelman, C.C.M. Kyba,
N. McCauley, V.L. Rusu, R. Van Berg
University of Pennsylvania
S.N. Ahmed, M. Chen, F.A. Duncan, E.D. Earle, B.G. Fulsom,
H.C. Evans, G.T. Ewan, K. Graham, A.L. Hallin, W.B. Handler,
P.J. Harvey, M.S. Kos, A.V. Krumins, J.R. Leslie,
R. MacLellan, H.B. Mak, J. Maneira, A.B. McDonald, B.A. Moffat,
A.J. Noble, C.V. Ouellet, B.C. Robertson,
P. Skensved, M. Thomas, Y.Takeuchi
Queen’s University
D.L. Wark
Rutherford Laboratory and University of Sussex
R.L. Helmer
TRIUMF
A.E. Anthony, J.C. Hall, J.R. Klein
University of Texas at Austin
T.V. Bullard, G.A. Cox, P.J. Doe, C.A. Duba, J.A. Formaggio,
N. Gagnon, R. Hazama, M.A. Howe, S. McGee,
K.K.S. Miknaitis, N.S. Oblath, J.L. Orrell, R.G.H. Robertson,
M.W.E. Smith, L.C. Stonehill, B.L. Wall, J.F. Wilkerson
University of Washington
Sudbury Neutrino
Observatory, SNO
1000 tonnes D2O
R
E
A
L
T
I
M
E
12 m Diameter
Acrylic Vessel
5-cm thick walls
Support Structure
for 9500 PMTs,
60% coverage
1700 tonnes Inner
Shielding H2O
5300 tonnes Outer
Shield H2O
Urylon Liner and
Radon Seal
One million pieces
transported down in the
10 foot square mine
cage and re-assembled under
ultra-clean conditions.
Sensitive to 8B n
Unique Feature: ‘Appearance’ of nx vs. ‘Disappearance’ of ne
Brookhaven Science Associates
U.S. Department of Energy
SNO – used 3 neutron detection methods
( 3 “different detectors” with possibly different systematics)
Phase I (D2O)
Phase II (salt)
Phase III (3He)
Nov. 99 - May 01
July 01 - Sep. 03
Summer 04 - Dec. 06
Published
Published
2 t NaCl. n captures on
35Cl(n, g)36Cl
s = 44 b
Observe multiple g’s
PMT array readout
Enhanced NC
In Progress
36 proportional counters
3He(n, p)3H
s = 5330 b
Observe p and 3H
PMT-independent
readout, event by event
n captures on
2H(n, g)3H
s = 0.0005 b
Observe 6.25 MeV g
PMT array readout
Good CC
35Cl+n
2H+n
6.25 MeV
5 cm
8.6 MeV
Several
g rays
One g ray
n
3H
p
3He
3H
36Cl
n + 3He  p + 3H
Signals in SNO (Monte Carlo, Renormalized)
Pure D2O
Plus Salt
X 0.45
X 1/3
NC Salt
(BP98)
Phase 1, D2O:
2002 NC Results
Phase 2, NaCl:
Improved NC
Signal, 2003
Results
~ 9 NHIT/MEV
SNO Energy Calibrations
6.13 MeV
19.8 MeV
252Cf
neutrons
n  d  t  g …  e
(Eg = 6.3 MeV)
b’s from 8Li
g’s from 16N and t(p,g)4He
NEUTRINO EVENT DISPLAYED
ON SNO COMPUTER SYSTEM
Chemistry in SNO
•
Purify the water with respect to radioactivity and nonradioactive chemical impurities.
•
Ion Exchange & Ultrafiltration, MnOx, HTiO, Vacuum &
Membrane De-gassing, Reverse Osmosis.
•
Assay the water for residual contamination: Need to sample
100’s of tonnes in time period short compared to radioactive
decay under study to reach sensitivity.
•
Optical clarity.
•
Biological Growth.
•
Add or remove salt (Phase II).
•
Maintain stability of water system: temperature, pressure,...
•
Control D2O inventory and ratio of H2O/ D2O.
An important enemy, 232Th Decay Chain…..
Require 232Th content
< 3.7 x 10-15 g/g in D2O
bs and gs interfere
with our signals at
low energies
g’s over 2.2 MeV
from 208Tl
 d+gn+p
Measure U/Th Backgrounds in D2O
Salt
Phase
Several g’s in U and Th chains will photodisintegrate deuteron
• In-situ:
– Low energy data
via Tl & Bi isotropy
• Ex-situ:
– Ion exchange
(224Ra, 226Ra)
– Membrane
degassing
– Count daughter
product decays
Radon
Calibration
Radial distributions for SNO Salt Data
0
550
600
(Reconstructed radius, cm/
600)3
700 cm
Sun-angle distributions for SNO Salt Data
n points:
Toward sun
Away from sun
Energy Spectra Extracted from Salt Data
Without Imposing known 8B Shape
Flux Values
(Updated 2006)
(106 cm-2 s-1)
nCC:
1.68(10)
nES:
2.35(27)
nNC:
4.94(43)
Electron kinetic energy
Spectral Shapes are Extracted from the
Salt Data, Not Assumed to Fit 8B Shape
 Difference in CC Flux Between Unconstrained and
Constraint = 0.11  0.05(stat) +0.06 -0.09(syst)
(units are 106 cm-2 s-1)
 Consistent with Hypothesis of No Spectral
Distortion
 CC / NC = 0.306  0.026 (stat)  0.024 (syst)
 n-e / total  1/3, n-m,t / total  2/3
 Result is independent of the solar model
Results from Salt Phase, LMA Is Favored
 Dm2 = 7.1 X 10-5 ev2, 12 = 32.5o
8B-Shape
Brookhaven Science Associates
U.S. Department of Energy
SNO SOLVED THE SOLAR NEUTRINO PROBLEM
SNO RESULTS, Salt + D2O
391 live days
SNO Results from Pure D2O
Results from
Other Exp’ts.
SNO CC
Result agrees
with Davis’
Cl value.
Measuring Neutrino Oscillation Parameters,
Narrowing the Available Phase Space
Solar Neutrinos
Solar Neutrinos
+ KamLAND 2003
(ne rate)
Agreement between oscillation parameters for n and n
Solar Neutrinos
+ KamLAND 2004
(ne rate+spectrum)
‘Discovery Era in Neutrino Physics Is Finished, Entering Precision Era’
13 value UNKNOWN.
From CHOOZ, only
have limit, < 11°
WHY SO SMALL?
Want to measure with
1% precision.
Dm232 =2.410-3 eV2
23  45
Atmospheric n
(Super-K)
nm  nt
Dm221 =7.8 10-5 eV2
12 =32
H2O
Accelerator n
(K2K)
ne  nm,t
LS
D2O
Solar n (SNO)
Reactor n
(KamLAND)
• Neutrinos oscillate, must have mass
• Evidence for neutrino flavor conversion ne
• SNO Solved Solar Neutrino Problem
nm
nt
SNO Phase III (NCD Phase)Began 2004, To Finish End of 2006
 3He Proportional Counters (“NC Detectors”)
40 Strings on 1-m grid
440 m total active length
nx
Detection Principle
2H
+ nx  p + n + nx - 2.22 MeV
3He
(NC)
PMT
+ n  p + 3H + 0.76 MeV
Physics Motivation
Event-by-event separation. Measure NC
and CC in separate data streams.
Different systematic uncertainties
than neutron capture on NaCl.
NCD array removes neutrons from CC,
calibrates remainder. CC spectral
shape.
NCD
n
Neutron Capture in the NCDs
~ 1200 n captures per year from solar n
n+
3He
p+
3H
(Q = 764 keV)
3H
3
573 keV
H
764 keV
p
p-t track fully
contained in
gas
hits wall
p hits wall
p
anode wire
NCD wall
3
H
191 keV
End view of an NCD with
representative ionization tracks
Idealized energy spectrum in a 3He proportional
counter. The main peak corresponds to the 764keV Q-value of the 3He(n, p)3H reaction.
NCD Energy Spectrum
Energy spectrum from
one deployed NCD string
with an Am-Be neutron
source.
191-keV shoulder from
proton going into the wall
764-keV peak
Other Recent Work from SNO
 Are analyzing NCD data (blind analysis)
 Are analyzing data on atmospheric muons and neutrinos
 Set new limit on hep flux, to be released very soon
 SNO is involved in SNEWS
 Published Periodicity Analysis of SNO data
- Did unbinned log likelihood analysis
- No unknown solar period seen
- Ruled out at 3.6 s level the positive claim by
Sturrock et al. from their Super-K data analysis
- Only variation that was seen was due to eccentricity
of Earth’s orbit, measured e = 0.0143  0.0086
THE FUTURE OF SNO
 SNO finished Phase I, with Pure D 2O, and Phase II,
with NaCl + D2O; now running NCDs for ~2 years.
 Will end beginning of January 2007.
 All analyses done blind.
 New UG facility, “SNO Lab” is funded, being built.
 Are planning a relatively low-cost new experiment,
“SNO+”, to use the existing SNO acrylic vessel, DAQ,
and infrastructure; remove the D2O, refill with LS.
 Goal of SNO+ is to detect low-energy solar n from
pep and CNO solar branches; see Borexino, LENS…
 Want to see transition from matter-dominated to
vacuum oscillations.
Brookhaven Science Associates
U.S. Department of Energy
SNOLAB
14m x 14m x 60m, Clean Area
THE END
Thank you for your attention.