1. Solar Neutrino Results from SNO
Kevin Graham
Carleton University

2. Ray Davis and John Bahcall

3. Solar Neutrino Measurements
understanding how the sun works
- solar neutrino problem
- solar neutrino flux measurements
- temporal/consistency evaluations
neutrino physics
- flavour change/oscillation
- MNSP parameters
- new physics?
2n oscillation probability
(modified by MSW for solar)

4. Solar Neutrino Spectra
8B Standard Solar Model
(5.69 ± 0.91)x106 cm2 s-1
18.77 MeV
hep SSM
(7.97 ± 1.24)x103 cm2 s-1

5. The SNO Detector 9438 Inward- Looking PMTs 2039 m to surface
91 Outward
Looking PMTs
(Veto)
12 m diameter
Acrylic vessel
Norite Rock
PMT Support
Structure (PSUP)
5300 tonnes
light water
~1000 tonnes
heavy water
1700 tonnes
light water

6. cosq = 1/(index of refraction) ~420
What We Measure
Cherenkov Light
cosq = 1/(index of refraction) ~420
PMT Measurements
position
charge
time
Reconstructed Event
-event vertex
-event direction
-energy
-isotropy

7. Neutrino Reactions in SNOCC n + d  p + p + e− e
Q = MeV
good measurement of ne energy spectrum
some directional info  (1 – 1/3 cosq)
ne only NC x n +  p d
Q = 2.22 MeV
measures total 8B n flux from the Sun
equal cross section for all n types ES n + e−  n + e− x x
low statistics
mainly sensitive to ne, some n and n
strong directional sensitivity

8. SNO Data Taking Phases Phase I (pure D2O): 306.4 live days
Te > 5 MeV
R < 550 cm
2928 events
n capture on D
Single 6.25 MeV g
High CC-NC corr.
Te constrained
Phase II (salty D2O):
391 live days
Te > 5.5 MeV
R < 550 cm
4722 events
n capture on Cl
Multiple g’s 8.6 MeV
High CC-NC corr.
Te unconstrained
Phase III
(3He n counters):
n capture on 3He
n + 3He g p + t
Channels indep.
gno correlation
Reduced NC
systematics
counters in and
collecting data
Initial Results
Recent Results
Now Running

9. Signal Extraction maximum likelihood fit of model PDF’s to data
event variables R (radial position) b14(isotropy) cosqsun and E(energy)
b14
CC-NC separation
cosqsun CC NC ES
ES separation
don’t use E g “energy-unconstrained” g fit out CC spectrum!

10. Results from Complete Phase IICC
2176+/-78 ES
279+/-26 NC
2010+/-85
#EVENTS
4722 candidate events
391 live days a
Flux Results
CC Energy Spectrum
Neutrino Flavour Change!
no significant
sterile or
NSI effects
Day/Night Asymmetry

11. Global analysis of solar and reactor data
“LMA I” only allowed
region
Maximal mixing
rejected at ~5 s
Solar + KamLAND

12. SNO Periodicity Analysis
search for sinusoidal periodicity in Phase I and Phase II data
used both a Lomb-Scargle periodogram and an unbinned maximum likelihood fit.
(see PRD , )
event arrival times are fit to:
(t) = N [1 + A cos(2pft+d)]
largest peak in combined data set occurs at a period of 2.4 days, with a significance statistic of S=8.8
Monte Carlo shows that 35% of simulated data sets give a peak at least this large.
No evidence for modulation in any of SNO's data.

13. hep < 2.3 x 104 cm-2 s-1 (90% C.L.) <2.9 SSM
Preliminary Phase I hep and Diffuse Supernova Neutrino Background
Observed: 2 events
Expected: ± 0.60 background
0.99 ± 0.09 signal
look in ‘high’ energy windows
for hep and DSNB signals 8B
hep
atm
DSNB
DSNB
for 22.9 < En/MeV < 36.9 :
flux limit: <70 cm-2s-1 (90%CL)
predicted flux: 0.2→1.5 cm-2s-1
hep < 2.3 x 104 cm-2 s-1 (90% C.L.)
<2.9 SSM

14. NCD Phase Data 3He + n  p + 3H + 0.76 MeV
event-by-event separation (pulse shape)
different systematic uncertainties
precision NC measurement

15. Characteristic 3He(n,p)t Spectrum from Calibration
Data from
3He NCD-Strings
Alpha
Background
Next adding
Pulse Shape
Discrimination
Fit
Characteristic 3He(n,p)t
Spectrum from Calibration

16. Summary So far: What is next:
8B neutrino results from first two phases
including fluxes, spectrum, D/N asymmetry
search for periodicity in data
hep and diffuse SN neutrino results
What is next:
first results from NCD phase
muon and atmospheric analysis
combined phase I and II results with lower energy threshold
supernova watch
other results to come!
flavour change
MSW effect
q12 and Dm2
solar physics

19. Solar Neutrinos 8B only tiny fraction of solar neutrinos
chlorine and gallium experiments
integrate over different chains
no real low energy spectrum
7Be interesting but large
model uncertainty
pep has small uncertainty
and at ‘right’ energy
can provide most physics

20. 2n oscillation probability <Ynm|Yne>
Neutrino Mixing
for two neutrino mixing
flavour eigenstates different
from mass eigenstates (like quark CKM)
e,m,t
1,2,3
2n oscillation probability <Ynm|Yne>
Experimental Parameters
L = distance to experiment
E = neutrino energy
Physics Parameters
Dm2=m12-m22
sin22q
appearance/disappearance

21. 3 Neutrinos + Matter Effect
3 neutrinos (at least) a4 model parameters
matter enhancement modifies oscillation amplitude (MSW effect) ne e W

22. Vacuum vs Matter Enhanced Survival Probability
start with
ne in sun
transition
region
matter
enhanced
oscillation
vacuum
oscillation ne
solar pp pep B

23. What do 8B n Measurements Tell Us?
Fluxes
- CC/NC ratio
Day/Night
- asymmetry
CC Energy Spectrum
-shape distortion
Increasing Δm2
Decreasing q
No. of CC events
6 MeV
13 MeV
hep-ph/ July Bandyopadhyay, Choubey, Goswami, Petcov, and Roy

24. Flux Results from Complete Phase IICC
2176+/-78 ES
279+/-26 NC
2010+/-85
#EVENTS
4722 candidate events
391 live days a
energy-unconstrained
results
Unconstrained Fit Key Systematics
CC NC
Energy scale
-0.9% +1.0%
-3.3% +3.8%
β14 mean
-4.0% +3.7%
-3.6% +4.5%
Radial scale
-2.6% +2.5%
-3.0% +3.3%
n capture
-2.3% +2.1%
Total
-5.4% +4.8%
-6.9% +7.7%
Neutrino Flavour Change!

25. Measured Total Flux and SSM Predictions
8B Flux
experimental
uncertainty smaller
than theoretical
for this sector of
solar neutrinos

26. Day-Night Asymmetries
ACC= ± (stat.) ± (syst.)
ANC= ± 0.086(stat.) ± (syst.)
AES= ± 0.198(stat.) ± (syst.)
Constraining ANC to be zero:
ACC= ± 0.063(stat.) ±0.032(sys.)
AES= ± 0.198(stat.) ±0.030(sys.)
Combined Pure D2O and Salt
No evidence for asymmetries from
matter effects in the earth

27. 2-n oscillation region defined by SNO
Allowed regions

28. Muon and atmospheric neutrino analysis