new results from the salt phase of sno kathryn miknaitis center for experimental nuclear physics and...
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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
The SNO Detector
Acrylic vessel (AV), 12 m diam.
1700 tonnes H2O inner shielding
1000 tonnes D2O
6800 feet (~2km) underground
5300 tonnes H2O outer shielding
~9500 PMTs, 54% coverage
SNO’s Three Reactions
-eppd (CC) eCharged Current:
Neutral Current:
npd (NC) xx
Elastic Scattering:
-- ee (ES) xx
•Detect the e-
• energy spectrum
• Weak directional sensitivity
e
•Detect the n through secondary capture
• No directional or neutrino energy info
•Detect the e-
•Mainly sensitive to
•Highly directional
e
-- ee (ES) xx
npd (NC) x x
-eppd (CC) e
NCx
CCESCCx
)154.0/1()(
Solar Neutrino Physics with SNO (I)
Measurement of the 8B Solar Neutrino Flux:
Flavor change:
)(154.0
e
e
ES
CC
e
e
NC
CC
Solar Neutrino Physics with SNO (II)
Spectrum
6 MeV 13 MeV
No.
of
CC
eve
nts
Increasing Δm2
Day
Night
ee
eee DN
DNA
)(2
Day-Night Asymmetry:
MSW Signatures MSW Parameter Constraints
hep-
ph/0
4063
28 J
uly
21 2
004
Ban
dyop
adhy
ay,
Cho
ubey
, Gos
wam
i, P
etco
v, a
nd R
oy
Global analysis of solar neutrino and KamLAND data from 2004
SNO measurements of CC/NC, spectrum, and day-night
asymmetry contribute to MSW constraints
“LMA region”
Pure D2O
Salt 3He
Nov. 99 - May 01 July 01 - Sep. 03 Nov 04 - Dec. 06
γγ
γ
35Cl 36Cl
36Cl*
nγ
2H 3H
3H*
n
n captures on deuterium
σ = 0.0005b
6.25 MeV γ
n captures on chlorine
σ = 44b
8.6 MeV multiple γs
n captures on 3He in discrete prop.
counter array
σ = 5330b
0.764 MeV
n + 3He p + 3H
p3H
5 cm
n
3HePRL 87, 071301, 2001PRL 89, 011301, 2002PRL 89, 011302, 2002
PRL 92, 181301, 2004(for first 254 days) nucl-ex/0502021391-DAY RESULTS!
npd (NC) xx Three ways to catch that neutron!
1. Higher capture cross-section means more neutrons detected
2. Boosts energy of NC events further above analysis threshold
…
3H 36Cl
2H+n
35Cl+n
6.25 MeV
= 0.0005 b = 44 b
8.6 MeVAdvantages of Salty D2O (I)
Define an “isotropy parameter” based on Legendre polynomials in θij
3. Multiple gammas for NC means light is more isotropic than for CC, ES
ij
4114 4
)(cos
jiijll P
Advantages of Salty D2O (II)
Statistical separation of CC, NC events with no constraint on the CC spectrum shape
20
Energy Isotropy
Direction Radius
Extracted Events:
391- day salt results!
4722 events, r<550cm, Teff>5.5MeV
(Patience! Energy spectrum coming up soon!)
CC: 2176 ± 78
NC: 2010 ± 85
ES: 279 ± 26
External neutrons: 128 ± 42
Backgrounds fixed in fit: 128
)syst.()stat.( 35.2
)syst.()stat.( 94.4
)syst.()stat.( 68.1
15.015.0
22.022.0
38.034.0
21.021.0
08.009.0
06.006.0
ES
NC
CC
391- day salt results!
)scm10
of units(In 126
029.0031.0)stat.(023.0340.0
NC
CC
Systematics
Dominant systematic uncertainties for the shape-unconstrained analysis:
Energy scale -0.9% +1.0%
-3.3% +3.8%
-1.6% +1.9%
β14 mean -4.0% +3.7%
-3.6% +4.5%
-1.2% +1.3%
Radial scale -2.6% +2.5%
-3.0% +3.3%
-2.6% +3.0%
Angular Res. -0.4% +0.4%
-0.2% +0.2%
-5.1% +5.1%
CC NC ES
For spectrum analysis:
Systematic uncertainties evaluated
in each extracted CC energy bin
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
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 D2OH2O radioactivity - uranium and thorium in the H2OAV radioactivity - radioactive decays in the acrylicPMT beta - gammas from decays in the PMTs
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)
DN
DNA
)(2Day-Night Asymmetries (I)
ACC and ANC are correlated (ρ = -0.532)
In standard neutrino oscillations, ANC should
be zero…
Day-Night Asymmetries (II)
ACC= -0.037 ± 0.063(stat.) ±0.032(syst.)
AES= 0.153 ± 0.198(stat.) ±0.030(syst.)
Constraining ANC to be zero:
In the pure-D2O phase,
(shape constrained, ANC constrained)
013.0012.0e 049.0070.0A
DN
DNA
)(2
Combine with analogous ACC from the salt phase:
Convert Super-Kamiokande AES to Ae, and combine with SNO:
040.0037.0A OD salt 2
027.0035.0A SK SNO
MSW Constraints
Previous global analysis of solar neutrino data
Global Solar, with
new salt results
Global Solar + KamLAND 766
ton-year data
09.007.0
2256.04.0
2
09.008.0
2254.43.2
2
45.0tan ,eV100.8 b)
45.0tan ,eV105.6 a)
m
m
Detection Principle
2H + x p + n + x - 2.22 MeV (NC)
3He + n p + 3H + 0.76 MeV
x
n
40 Strings on 1-m grid
440 m total active length
NCD
PMT
SNO Phase III (NCD Phase)
3He Proportional Counters (“NC Detectors”) now installed Production data taking underway
Physics Motivation
Event-by-event separation. Measure NC and CC in separate data streams.
Different systematic uncertainties than neutron capture on NaCl.
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:
09.007.0
2256.04.0
2 45.0tan ,eV100.8
m