SNO Update

1
SNO Review Comparisons NOW 2004 12 September
2004
Mark Chen Queens University The Canadian
Institute for Advanced Research
2
The SNO Collaboration
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 Queens 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

• 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

3
Sudbury Neutrino Observatory
1000 tonnes D2O 12 m diameter Acrylic Vessel 18 m
diameter support structure 9500 PMTs (60
photocathode coverage) 1700 tonnes inner
shielding H2O 5300 tonnes outer shielding
H2O Urylon liner radon seal depth 2092 m (6010
m.w.e.) 70 muons/day
4
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 active n flavors

?

e-
n
e-
n
ES
x
x

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

5
SNO Neutral Current Trilogy
Pure D2O Nov 99 May 01 n ? d ? t ? g (Eg 6.25
MeV) good CC PRL 87, 071301 (2001) PRL 89,
011301 (2002) PRL 89, 011302 (2002) D2O Archival
Long Paper in progress
Salt Jul 01 Sep 03 n ? 35Cl ? 36Cl ? ?g (E?g
8.6 MeV) enhanced NC and event isotropy PRL 92,
181301 (2004) Long Salt Paper soon to be
submitted
3He Counters Fall 04 Dec 06 n ? 3He ? t ?
p proportional counters s 5330 b event-by-event
separation First NCD Paper in the future
6
SNO Phase III 3He Detectors
3He Proportional Counters (NC Detectors)
Detection Principle 2H ?x ? p n ?x - 2.22
MeV (NC) 3He n ? p 3H 0.76 MeV
40 Strings on 1-m grid 398 m total active length
Physics Motivation Event-by-event separation.
Measure NC and CC in separate data streams.
Different systematic uncertainties than
neutron capture on NaCl. 3He array removes
neutrons from CC, calibrates remainder. CC
spectral shape.
7
Structure of this Talk Comparison of Phases

• signals
• backgrounds
• energy and optics
• flux
• spectral shape
• day-night analysis
• oscillation analysis

8
Cerenkov Detection
PMT Measurements

• position
• charge
• time

Reconstructed Event
-event vertex -event direction -energy -isotropy
9
Signal Extraction Pure D2O

• signal PDFs
• energy
• R3 (radius)
• cos qSun
• Monte Carlo
• maximum likelihood fit with background amplitudes
  fixed

10
Signal Extraction Salt Phase
statistical signal separation extended maximum
likelihood
energy
R3
use R3, cos qSun, b14
event isotropy
cos qSun
b14
perform signal extraction w/o any spectral shape
assumptions
11
NaCl Neutron Detection

• higher capture cross section
• higher energy release
• many gammas

s 44 b
35Cln
s 0.0005 b
8.6 MeV
2Hn
6.3 MeV
3H
36Cl
12
Neutron Capture Efficiency
35Cl(n,g)36Cl ltegt 0.399 0.010 Te 5.5 MeV
and Rg 550 cm
2H(n,g)3H ltegt 0.144 0.005 Te 5.0 MeV and
Rg 550 cm
252Cf fission neutron source
2 tonnes of NaCl added to 1000 tonnes heavy water
13
Simulated Neutron Event in D2O

• neutron events in pure D2O look very similar to
  single electrons

14
Simulated Neutron Event in Salt

• neutron events in salt are more isotropic

15
Cerenkov Light and b14
hollow cone of emitted photons
qij
e- (v gt c/n)
)
43o
sum over all pairs of PMT hits
b14 b1 4b4
16
Monte Carlo Signal Separation
17
Neutron Signals from the First NCD

• data taken on the J3 string (first 9.5 m long
  NCD) with the AmBe source on 12/02/03 at 2238
  EST
• bin 135 is about 764 keV
• total number of neutrons in the peak roughly
  matches Monte Carlo prediction

18
Comparison of Phases

• signals ?
• backgrounds
• energy and optics
• flux
• spectral shape
• day-night analysis
• oscillation analysis

19
Sources of Background

• g d ? p n, from 214Bi (U chain), 208Tl (Th
  chain)
• cosmic rays neutrons, spallation products
• atmospheric neutrinos, reactors, CNO electron
  capture
• fission (U, Cf)
• (a,n) reactions
• 24Na activation (neck, calibration,
  recirculation, muons)
• AV events
• focus is on neutron backgrounds to the NC

20
Pure D2O Water Assays
targets for D2O represent a 5 background from g
d ? n p
targets are set to reduce b-g events
reconstructing inside 6 m
21
Salt Phase Water Assays

• bottom of vessel
• 2/3 way up
• top of vessel

salted D2O radioactivity should produce 0.72
0.24 neutrons per day pure D2O radioactivity was
estimated at 1.0 0.2 neutrons per day the SSM
rate of NC events would produce 13.1 neutrons per
day

• MnOx
• HTiO

• MnOx
• HTiO

22
New Salt Phase Background

• 24Na activation
• neutrons activate 23NaClsalty D2O can be
  activated outside the detector and brought in by
  circulation

• d ? p n
• NC background and low-energy gs

t1/2 14.95 hr
23
External 24Na Introduced
Salt Injected on May 28, 2001
24Na Background
The NaCl brine in the underground buffer tank was
activated by neutrons from the rock wall. We
observed the decay of 24Na after the brine is
injected in the SNO detector.
t1/214.95 hrs
24
External Neutrons

• light water gs photodisintegrate deuteron
• radon daughters deposited on the acrylic vessel
  during construction
• 210Pb has t1/2 22 years
• feeds 210Po which alpha decays
• (a,n) on 13C, 17O, 18O
• neutrons originate from the AV

pure D2O phase
salt phase
estimated from radioassays, 27 8 events
subtracted
fit both
was not considered
25
Fitting External Neutron Backgrounds

• efficient neutron capture on Cl

improved separation of internal and external
background neutrons
r(R cm/600)3
26
Salt Phase Backgrounds Table
Source Number of Events
deuteron photodisintegration 73.1
2H(a,a)pn 2.8 0.7
17,18O(a,n) 1.4 0.9
fission, atmospheric ns 23.0 7.2
terrestrial and reactor ns 2.3 0.8
neutrons from rock lt1
24Na activation 8.4 2.3
neutrons from CNO ns 0.3 0.3
total internal neutron background 111.3 25
internal g (fission, atmospheric n) 5.2 1.3
16N decays lt 2.5 (68 CL)
external-source neutrons (from fit) 84.5 34
Cerenkov events from PMT b-g lt14.7 (68 CL)
AV events lt 5.4 (68 CL)
24.0 -25.5
27
NCD Backgrounds Pulse Shape
current preamplifiers digitize pulse shapes for
particle identification
28
Comparison of Phases

• signals ?
• backgrounds ?
• energy and optics
• flux
• spectral shape
• day-night analysis
• oscillation analysis

29
Optical Calibrations

• manipulator positioning accuracy 2 cm
• laserball moved throughout detector (in two
  planes)
• extract optical parameters (D2O attenuation, PMT
  angular response, H2O attenuation) at various
  wavelengths

B. Moffat with dye laser and laserball
30
16N Calibration Source

• internally triggered
• used for
• energy scale
• energy drift
• detector radial response
• energy resolution
• vertex resolution
• angular resolution

M. Boulay with 16N source
31
Detector Energy Drift
32
Monitoring Detector Optics

• D2O attenuation increasing
• water chemistry analyses reveal increasing Mn and
  organics
• consistent with light absorption feature at 420
  nm

33
Salt Energy Scale Drift
energy scale drift agrees with MC
prediction coming from slight increase in D2O
photon absorption over time
34
Desalination

reverse osmosis

• started 09/09/2003
• pass 1 completed 09/14/2003100x reduction

35
Pass 1 Stratification

• salt probe conductivity measurement

salt water more dense
salt interface remained solid throughout operation
purified D2O floats
probe z position cm
36
Na and Impurities Removed
Limit Feed Permeate
Mn lt2 ppb 15 ppb 0.1 ppb
Cr lt1 ppb 0.6 ppb 0.04 ppb
Fe lt1.5 ppb lt10 ppb lt1.5 ppb
Ni lt20 ppb lt0.8 ppb lt0.08 ppb
Cu lt40 ppb lt3 ppb lt1 ppb
TOC lt10 ppb 20 ppb 3-4 ppb
feed
permeate
37
Optics Restored Confirmation!
salt phase energy drift
-1.8 per year due to D2O attenuation
desalination pass 1
Mn and/or TOC light absorption removed!
38
Optics Destroyed! in NCD Phase ?

• example of a current NCD phase optics
  calibration
• occupancy map from laserball source in the centre
  of the detector
• working now to understand the detector (PMTs and
  NCDs)

39
Comparison of Phases

• signals ?
• backgrounds ?
• energy and optics ?
• flux
• spectral shape
• day-night analysis
• oscillation analysis

40
SNO Pure D2O Results (2002)
306.4 days
12-12
neutron background 78 primarily g d ? p
n Cerenkov background 45
18-12
41
Constrained Shape Fluxes
Ethreshold gt 5 MeV
En gt2.2 MeV
Fcc(ne) 1.76 (stat.) (syst.) 106
cm-2s-1 Fes(nx) 2.39 (stat.)
(syst.) 106 cm-2s-1 Fnc(nx) 5.09
(stat.) (syst.) 106 cm-2s-1

0.05 -0.05
0.09 -0.09
Fe 1.76 (stat.) (syst.) 106 cm-2s-1 Fmt
3.41 (stat.) (syst.) 106 cm-2s-1
0.45 -0.45
0.48 -0.45
more than just ne coming from the Sun!
42
Salt Phase 254.2 neutrino live-days
Energy Spectra
Radial
Light Isotropy
Sun-angle dist.
43
SNO Salt Fluxes
shape of 8B spectrum in CC and ES not constrained
44
Uncertainties in Fluxes ()
energy scale
resolution
radial accuracy
angular resolution
isotropy mean
isotropy width
radial E bias
internal neutrons
Cerenkov bkds
AV events
neutron capture
total
45
Total Active 8B Fluxes
in units of Bahcall, Pinsonneault, Basu 2001 SSM,
5.05 x 106 cm-2 s-1

• results are consistent with SSM and with each
  other
• uncertainty in total flux reduced in the new
  salt result, even while constraints were relaxed

0.20 -0.16
BPB01 SSM 1.00
Junghans et al. nucl-ex/0308003 1.16 0.16
BP04 SSM 1.15 0.26
SNO D2O (constrained) 1.01 0.13
SNO D2O (unconstrained) 1.27 0.33
SNO Salt (unconstrained) 1.03 0.09
new S17
46
Next Salt Paper Fluxes

• 254.2 days to 391.4 days, increased statistics
• improved systematics determinations (does not
  mean all systematics have become smaller!)

47
NCD Phase Fluxes

• good statistics
• CC, NC break correlations
• smaller systematic uncertainties

  D2O unconstrained D2O constrained Salt unconstrained 3He
NC,CC -0.950 -0.520 -0.521 0
CC,ES -0.208 -0.162 -0.156 -0.2
ES,NC -0.297 -0.105 -0.064 0
48
Comparison of Phases

• signals ?
• backgrounds ?
• energy and optics ?
• flux ?
• spectral shape
• day-night analysis
• oscillation analysis

49
Pure D2O Energy Spectrum
tan2q
Day Spectrum CCNCES
0.9 0.8 0.7 0.6 0.5 0.4 0.3
would be worse with salt
Dm2 8 10-5 eV2
50
Salt Extracted CC Spectral Shape
tan2q
CC Spectral Shape
0.9 0.8 0.7 0.6 0.5 0.4 0.3
rate/SSM
recoil electron total energy MeV
Dm2 8 10-5 eV2
51
Salt CC Spectral Systematics

• bin-bin statistical correlations from likelihood
  extraction and for various systematics determined
• most systematics are small for the integrated CC
  flux measurementbut, not necessarily small in
  each spectral bin
• energy dependence and biases investigated and
  understood
• to be presented soon in the upcoming paper

52
NCD Phase Spectra

• 3He counters soak up the neutrons
• will allow a cleaner look at low energy CC events
• will still be some neutron captures by deuterons
  in the heavy water these can be calibrated and
  subtracted using the NCD neutron count rate

53
Comparison of Phases

• signals ?
• backgrounds ?
• energy and optics ?
• flux ?
• spectral shape ?
• day-night analysis
• oscillation analysis

54
Pure D2O Day-Night Spectra
night rate 9.79 0.24 d-1 day rate 9.23 0.27
d-1
define asymmetry A 2 (N D)
(N D)
night - day
1.3

• Ae 7.0 4.9

-1.2
55
Can SNO Observe Day-Night Effect?
tan2q
0.3 0.4 0.5 0.6 0.7 0.8 0.9
2.5 in CC
5.7 -1.6
1.1 -0.4
3.3
0.6
Bahcall, Gonzalez-Garcia, Peña-Garay
56
Comparison of Phases

• signals ?
• backgrounds ?
• energy and optics ?
• flux ?
• spectral shape ?
• day-night analysis ?
• oscillation analysis

57
Oscillations Analysis Before SNO
this figure updated and upgraded
before SNO Fogli, Lisi, Montanino Palazzo
after SNO Pure D2O SNO Collaboration
58
Oscillation Analysis Global Solar
Before Salt
After Salt
--90 --95 --99 --99.73
59
Oscillation Analysis Before
solar solar plus KamLAND
LMA
Bahcall, Gonzalez-Garcia, Peña-Garay
LMA-II
LOW
LMA-I
pre-salt
60
Oscillation Analysis After Salt
solar solar plus KamLAND
-90 -95 -99 -99.73
global solar finds only LMA
LMA-I only at gt 99 CL
61
Salt PRL Fluxes New KamLAND
log-log plot in tan2q

• including KamLAND Neutrino 2004 results

62
Synopsis of SNO Salt Results
sin2q12 0.29 0.04
next salt paper oscillation analysis will include
salt day-night, CC spectral shape
63
Global Solar NCD Projection with and w/o KamLAND
lin-lin plot in tan2q
SNO will constrain the mixing angle...
64
Comparison of Phases

• signals ?
• backgrounds ?
• energy and optics ?
• flux ?
• spectral shape ?
• day-night analysis ?
• oscillation analysis ?

65
Summary
1998
1999
2000
2001
2002
2003
2004
2005
2006
NOW
Pure D2O
commissioning
Salt
3He Counters
added 2 ton of NaCl
Pure D2O and desalination

• pure D2O phase discovers active solar neutrino
  flavors that are not ne
• salt phase moves to precision determination of
  oscillation parameters flux determination has no
  spectral constraint (thus can use it rigorously
  for more than just the null hypothesis test)
• NCDs installed and about to begin production
  data taking final SNO configuration offers CC
  and NC event-by-event separation, for improved
  precision and cleaner spectral shape examination

66

• fin