New Results from the

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New Results from the Salt Phase of SNO
Kathryn Miknaitis Center for Experimental
Nuclear Physics and Astrophysics, Univ. of
Washington For the Sudbury Neutrino Observatory

• In this talk
• SNO overview
• Salt phase overview
• New solar neutrino flux, spectrum, and day-night
  asymmetry results from 391 days of salt data!

The Sudbury Neutrino Observatory
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The SNO Detector
6800 feet (2km) underground
Acrylic vessel (AV), 12 m diam.
1000 tonnes D2O
1700 tonnes H2O inner shielding
5300 tonnes H2O outer shielding
9500 PMTs, 54 coverage
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SNOs Three Reactions
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Solar Neutrino Physics with SNO (I)
Measurement of the 8B Solar Neutrino Flux
Flavor Change
Flavor change
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Solar Neutrino Physics with SNO (II)
MSW Signatures
MSW Parameter Constraints
hep-ph/0406328 July 21 2004 Bandyopadhyay,
Choubey, Goswami, Petcov, and Roy
Day-Night Asymmetry
LMA region
Global analysis of solar neutrino and KamLAND
data from 2004 SNO measurements of CC/NC,
spectrum, and day-night asymmetry contribute to
MSW constraints
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Three ways to catch that neutron!
Pure D2O
Salt
3He
Nov. 99 - May 01
July 01 - Sep. 03
Nov 04 - Dec. 06
n captures on deuterium s 0.0005b 6.25 MeV ?
n captures on 3He in discrete prop. counter
array s 5330b 0.764 MeV
n captures on chlorine s 44b 8.6 MeV multiple ?s
PRL 92, 181301, 2004 (for first 254 days)
nucl-ex/0502021 391-DAY RESULTS!
PRL 87, 071301, 2001 PRL 89, 011301, 2002 PRL 89,
011302, 2002
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Advantages of Salty D2O (I)
1. Higher capture cross-section means more
neutrons detected 2. Boosts energy of NC events
further above analysis threshold
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Advantages of Salty D2O (II)
qij
3. Multiple gammas for NC means light is more
isotropic than for CC, ES
Define an isotropy parameter based on Legendre
polynomials in ?ij
Statistical separation of CC, NC events with no
constraint on the CC spectrum shape
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Energy
Isotropy
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Radius
Direction
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391- day salt results!
4722 events, rlt550cm, Teffgt5.5MeV
Extracted Events
CC 2176 78 NC 2010 85 ES 279
26 External neutrons 128 42 Backgrounds fixed
in fit 128
(Patience! Energy spectrum coming up soon!)
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Systematics
Dominant systematic uncertainties for the
shape-unconstrained analysis
CC NC ES
For spectrum analysis Systematic uncertainties
evaluated in each extracted CC energy bin
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CC Spectrum
Extracted CC spectrum with statistical and
systematic uncertainties
Extracted CC spectrum with statistical
uncertainties, compared to model predictions
CC spectrum consistent with LMA, undistorted 8B
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Systematics for the Day-Night Analysis
DN Correlated Uncertainties overall energy
scale uncertainty cancel in
asymmetry ratio Differential Uncertainties
time variations (diurnal and long term)
evaluate with in-situ techniques geometric
uncertainties evaluate with
calibration data
Classes of Events Used to Limit Diurnal
Variations Muon Followers neutrons induced
by cosmic ray muons Hot Spot - radioactive spot
on the acrylic vessel (AV) D2O radioactivity -
uranium and thorium in the D2O H2O radioactivity
- uranium and thorium in the H2O AV radioactivity
- radioactive decays in the acrylic PMT beta -
gammas from decays in the PMTs
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Day-Night Asymmetries (I)
ACC -0.056 0.074 (stat.) 0.051 (syst.) ANC
0.042 0.086(stat.) 0.067 (syst.) AES 0.146
0.198(stat.) 0.032 (syst.) (CC, ES spectrum
shapes unconstrained in this analysis)
ACC and ANC are correlated (? -0.532) In
standard neutrino oscillations, ANC should be
zero
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Day-Night Asymmetries (II)
Constraining ANC to be zero
ACC -0.037 0.063(stat.) 0.032(syst.) AES
0.153 0.198(stat.) 0.030(syst.)
Combine with analogous ACC from the salt phase
Convert Super-Kamiokande AES to Ae, and combine
with SNO
In the pure-D2O phase, (shape constrained, ANC
constrained)
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MSW Constraints
Previous global analysis of solar neutrino data
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SNO Phase III (NCD Phase)

• 3He Proportional Counters (NC Detectors) now
  installed
• Production data taking underway

40 Strings on 1-m grid 440 m total active
length
Detection Principle 2H ?x ? p n ?x - 2.22
MeV (NC) 3He n ? p 3H 0.76 MeV
PMT
Physics Motivation Event-by-event separation.
Measure NC and CC in separate data streams.
Different systematic uncertainties than
neutron capture on NaCl.
NCD
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Conclusions

• Results from full 391-day salt phase available
  nucl-ex/0502021
• Solar neutrino flux results confirm and improve
  previous results
• CC spectrum presented, consistent with LMA
  prediction (also consistent with no distortion)
• Day-Night asymmetries consistent with LMA
  prediction (also with no asymmetry)
• MSW mixing parameters