The n Odyssey 2002: SNO

1
The n Odyssey 2002SNO KamLAND

• Alan Poon
• (for the SNO and KamLAND Collaborations)
• Institute for Nuclear and Particle Astrophysics
• Lawrence Berkeley National Laboratory, Berkeley,
  USA

2
Outline

• Introduction the Solar Neutrino Problem
• Demonstration of Solar Neutrino Flavour
• Transformation (ne?nm,t)
• Sudbury Neutrino Observatory
• Testing Solar Neutrino Oscillation Hypothesis
  Using Reactor Anti-Neutrinos
• Kamioka Liquid Scintillator Anti-Neutrino
  Detector
• Outlook

3
Solar Model Prediction of Solar ne Flux
pp chain 4p 2e ? 4He 2ne 26.7 MeV
Detailed computer model of solar evolution
Standard Solar Model
4
Solar Neutrino Problem (circa 2000)
either Solar models are incomplete/incorrect or Ne
utrinos undergo flavor-changing transformation
5
A Proposal to Hunt for the Missing ns
Phys. Rev. Lett. 55, 1534 (1985)
6
Sudbury Neutrino Observatory
1006 tonnes D2O
17.8m dia. PMT Support Structure 9456 20-cm dia.
PMTs 56 coverage
12.01m dia. acrylic vessel
1700 tonnes of inner shielding H2O
Urylon liner
5300 tonnes of outer shielding H2O
Nucl. Inst. Meth. A449, 127 (2000)
7
Detecting ? at SNO

• Measurement of ne energy spectrum
• Weak directionality

• Measure total 8B n flux from the sun
• s(ne) s(nm) s(nt)

• Low Statistics
• s(ne) ? 6 s(nm) ? 6 s(nt)
• Strong directionality

8
Lets Go Catch Some Zs
The physics program at SNO is tailored to measure
the total solar n flux via the Neutral-Current
reaction with different systematics
Phase II (dissolved NaCl)
Phase III (3He n counters)
Phase I (pure D2O)
Neutron capture on D
Neutron capture on Cl
n ? 3He ? p ? t
Single 6.25 MeV g
g cascade, 8.6 MeV
Statistical separation (Energy, radius)
Statistical separation (Light Isotropy)
Independent channel
NC uncorrelated to CC
High CC-NC correlation
Better CC-NC separation
Past (Nov 99 to May 01)
Present (since June 01)
Future
(Sep 03 ??)
9
Analysis Example Energy Response (SNO Phase I)

• Calibration
• PMT Optics
• Normalized to 16N Eg6.13 MeV
• Check with
• 8Li 13 MeV b
• 252Cf d(n,g), Eg6.25 MeV
• 3H(p,g) 19.8 MeV g

DE/E 1.21 Ds/s 4.5 Linearity 0.23
_at_ Ee19.1 MeV
Energy?
10
Extracting the Solar n Flux (SNO Phase I)
CC
NC
ES
Max. Likelihood Fit

• PDFs
• kinetic energy T, event location R3,
• and solar angle correlation cos qsun

11
Signal Extraction Results (SNO Phase I)

• 306 live days (Nov 1999 to May 2001)

Assume standard 8B n spectrum Null hypothesis
no neutrino flavour transformation
61.9 -60.9
CC 1967.7 events NC 576.5
events ES 263.6 events
49.5 -48.9
26.4 -25.6
12
Flux Uncertainties (Shape constrained)
fCC
fNC
13
Missing Solar ns Found
Null hypothesis of no flavour transformation
rejected at 5.3s
See Phys.Rev.Lett. 89 (2002) 011301
Phys.Rev.Lett. 89 (2002) 011302
Solar Model predictions are verified in 106
cm-2 s-1
8B n shape constrained fit
No 8B n shape constraint
14
Corrections Made Accordingly
15
Corrections Made Accordingly
16
Correlation in Signal Extraction (Phase I)
Strong statistical anti-correlation between NC
and CC in the signal extraction
Correlation Matrix
CC ES NC
CC 1.000 -0.162 -0.520
ES -0.162 1.000 -0.105
NC -0.520 -0.105 1.000
17
Light Isotropy in Phase II

• CC and ES signals yield an electron, which
  produces a single cone of Cherenkov light
• In Phase I (pure D2O), NC signal yields a single
  g, whereas in Phase II (salty D2O) there are
  multiple gs following n capture on 35Cl
• We can use light isotropy to help distinguish CC
  and NC

18
Light Isotropy in Phase II
Variables CC Stat. Error NC Stat. Error ES Stat. Error
E,R,?sun 3.4 8.6 10
R, ?sun 9.5 24 11
E,R,?sun 4.2 6.3 10
E,R,?sun, Iso. 3.3 4.6 10
R,?sun,Iso. 3.8 5.3 10

Published D2O

Preliminary
Simulated D2O NaCl
Simulations assume 1 yr of data, with .35 SSM for
CC, .5 SSM for ES, and 1 SSM for NC. PRL,
89, No. 1, 011301, (2002)
19
Decoupling CC and NC in Phase III

• CC Cherenkov Signal ? PMT Array
• NC n3He ? Neutral Current Detector Array

20
SNO Summary
Phase II (D2ONaCl)

• Final full-scale detector calibration before the
  removal of salt is in progress
• Salt to be removed in about a month
• Intense analysis activities in progress

Phase III (Neutral Current Detector)

• All 3He counters have been constructed and
  stored in the underground lab
• Integration of electronics and DAQ in progress
• Deployment in September 2003

21
2-Flavor Neutrino Oscillation
Weak states (nW) (participate in weak
interactions)
Mass states (nM) mass m1, m2
Note May also have resonant flavor conversion
in matter Mikheyev-Smirnov-Wolfenstein (MSW)
effect
22
Global Solar n Analysis

• Inputs 37Cl, latest Gallex/GNO, new SAGE, SK
  1258-day day night spectra
• SNO day spectrum (total CCNCESbackground)
• SNO night spectrum (total CCNCESbackground)
• 8B floats free in fit, hep n at 1 SSM

Global
SNO data only
23
If CPT is conserved(and LMA)
Predicts deficit in
Solar ne
Reactor ne
100 to 200 km
Complementary!
24
Is n Oscillation Really the Solution?

• Kamioka Liquid scintillator Anti-Neutrino
  Detector (KamLAND)
• (Kamioka, Gifu Prefecture, Japan)
• reactor n _at_ right baseline for directly
  testing the currently favoured LMA region

1 kt liquid scintillator as target
2x coincidence
(inverse b decay)
25
The KamLAND Detector

• 1 kton liquid scintillator
• 80 mineral oil
• 20 pseudocumine
• 1.5 g/L PPO (fluor)
• r0.78 g/cm3
• Mineral oil outside a 130-mm thick, 13-m
  diameter nylon balloon
• r0.76 g/cm3
• A 3-mm thick acrylic radon barrier at 16.6-m
  diameter to reduce Rn
• 1879 PMT's
• 1325 17 brand new
• 544 20 from K-II
• 34 photocathode coverage
• 225 Veto 20 PMT's from K-II
• Water Cherenkov

26
Why Kamioka?
LMA
51 reactors in Japan, 80 of flux (or 68.5 GW of
reactor power) from baseline of 140 to 210 km
27
KamLAND Construction
Autumn 1999 Steel sphere construction
Summer 2000 PMT installation
Winter 2000 Veto counter installation
February 2001 Balloon insertion
April-May 2001 Plumbing for fill
June-Sept. 2001 Mineral oil and liquid scintillator fill
Early Sept. 2001 Electronics/DAQ integration
Late Sept. 2001 First data taking
Jan. 22, 2002 Production data taking began
Dec. 6, 2002 First paper submitted
28
Position Reconstruction Uncertainty
68Ge 1.012 MeV (? ?) 65Zn
1.116 MeV (?) 60Co 2.506 MeV (? ?)
AmBe 2.20, 4.40, 7.6 MeV (?)
-5 m
5 m
Position resolution 25 cm. Vertex
reconstruction based on photon arrival times.
29
Energy Calibration
65Zn (1.115 MeV g)
60Co (2.505 MeV gg)
Light yield 300 p.e./MeV
30
Radioactive Background
31
Reactor Anti-Neutrino Flux Analysis
Data Sample Mar. 4 Oct. 6, 2002 162
tonyr (145.1 days) 370M raw events
prompt
delayed

• Inverse ?-decay selection
• no m veto signals
• Eprompt lt 30 MeV
• 0.5 lt ?T lt 660 msec
• ?R lt 1.6 m, Rd gt 1.2 m
• 1.8 lt Edelayedlt 2.6 MeV
• R lt 5 m 409 ton, 3.46x1031 free protons
• ? tagging efficiency 78.3

g from n12C
Fitted correlation time between prompt and
delayed sub-event ?t188 23 ?s ? In
agreement with expectation for thermal n-capture.
32
Reactor Anti-Neutrino Flux Results
Eprompt gt 2.6 MeV (to remove geo-n)
Systematic Uncertainties Systematic Uncertainties Systematic Uncertainties Systematic Uncertainties
Detector related Source related
Total LS mass 2.1 Reactor power 2.0
Fiducial mass ratio 4.1 Fuel composition 1.0
Energy threshold 2.1 Time lag 0.28
Cut efficiency 2.1 v spectra 2.5
Live time 0.7 Cross section 0.2
Total Total 6.4 6.4
Observed 54 events Expected 86.8
5.6 events Background 1 1 events
accidental 0.0086 0.0005 9Li/8He
0.94 0.85 fast neutron lt 0.5
Probability that result is consistent with no
oscillation hypothesis lt 0.05
33
Reactor Anti-Neutrino Flux
First observation of reactor anti-neutrino deficit
34
Prompt Energy Spectrum
E?(geo) lt 2.49 MeV
35
Spectral Distortion?
No oscillation, flux suppression
2-? oscillation best-fit
Data and best oscillation fit consistent at 93
C.L.
Data and scaled no-oscillation shape consistent
at 53 C.L
Need more reactor neutrino and calibration data
36
KamLAND Summary
KamLAND reactor antineutrino experiment (1st
phase)

• KamLAND detector is routinely taking data since
  January 2002.
• Detector background and energy resolution are
  better than expected.
• Analysis of first 145 days of data shows clear
  event deficit.
• ? After 50 years, first evidence for reactor ?e
  disappearance.
• Data taking continues. ? Probe spectral
  deformations and perform precision measurement of
  neutrino mixing parameters.

KamLAND 7Be solar neutrino and geo-neutrino
experiment (2nd phase) Will require lower
backgrounds, possibly purification and
re-circulation of scintillator and buffer oil
RD effort underway at Tohoku U.
37
2-n Mixing Paremeters
Rate Shape (gt2.6 MeV) Best Fit ?m2 6.9 x
10-5 eV2 sin2 2? 1.0 Rate Shape (gt0.9 MeV)
fit with the additional free parameters of
geo-neutrino backgrounds are consistent with the
results above
38
What will SNO and KamLAND tell us in the future?
de Holanda et al., hep-ph/0212270 Barger et al.,
hep-ph/0204253
39
Summary

• Solar Neutrino Problem solved, and much have been
  learned about neutrino mixing

Stay TunedMore have yet to come!
40
The SNO Collaboration
J.D.Anglin, M.Bercovitch, W.F.Davidson,
R.S.Storey National Research Council of
Canada J.C.Barton, S.Biller, R.A.Black,
R.J.Boardman, M.G.Bowler, J.Cameron,
B.T.Cleveland, X.Dai, G.Doucas,
J.A.Dunmore, A.P.Ferarris, H.Fergani, K.Frame,
N.Gagnon, H.Heron, N.A.Jelley, A.B.Knox, M.Lay,
W.Locke, J.Lyon, S.Majerus, G.McGregor, M.Moorhead
, M.Omori, C.J.Sims, N.W.Tanner,
R.K.Taplin, M.Thorman, P.M.Thornewell, P.T.Trent,
N.West, J.R.Wilson University of
Oxford E.W.Beier, D.F.Cowen, M.Dunford,
E.D.Frank, W.Frati, W.J.Heintzelman, P.T.Keener,
J.R.Klein, C.C.M.Kyba, N.McCauley, D.S.McDonald,
M.S.Neubauer, F.M.Newcomer, S.M.Oser, V.L
Rusu, R.Van Berg, P.Wittich University of
Pennsylvania   R.Kouzes Princeton
University E.Bonvin, M.Chen, E.T.H.Clifford,
F.A.Duncan, E.D.Earle, H.C.Evans, G.T.Ewan,
R.J.Ford, K.Graham, A.L.Hallin, W.B.Handler,
P.J.Harvey, J.D.Hepburn, C.Jillings,
H.W.Lee, J.R.Leslie, H.B.Mak, J.Maneira,
A.B.McDonald, B.A.Moffat, T.J.Radcliffe,
B.C.Robertson, P.Skensved Queens
University D.L.Wark Rutherford Appleton
Laboratory, University of Sussex R.L.Helmer,
A.J.Noble TRIUMF Q.R.Ahmad, M.C.Browne,
T.V.Bullard, G.A.Cox, P.J.Doe, C.A.Duba,
S.R.Elliott, J.A.Formaggio, J.V.Germani, A.A.Hamia
n, R.Hazama, K.M.Heeger, K.Kazkaz, J.Manor,
R.Meijer Drees, J.L.Orrell, R.G.H.Robertson,
K.K.Schaffer, M.W.E.Smith, T.D.Steiger,
L.C.Stonehill, J.F.Wilkerson University of
Washington

• G.Milton, B.Sur
• Atomic Energy of Canada Ltd., Chalk River
  Laboratories
• S.Gil, J.Heise, R.J.Komar, T.Kutter, C.W.Nally,
  H.S.Ng,
• Y.I.Tserkovnyak, C.E.Waltham
• University of British Columbia
• J.Boger, R.L Hahn, J.K.Rowley, M.Yeh
• Brookhaven National Laboratory
• R.C.Allen, G.Bühler, H.H.Chen
• University of California, Irvine
•  
• I.Blevis, F.Dalnoki-Veress, D.R.Grant,
  C.K.Hargrove, I.Levine,
• K.McFarlane, C.Mifflin, V.M.Novikov, M.O'Neill,
  M.Shatkay,
• D.Sinclair, N.Starinsky
• Carleton University
•  
• T.C.Anderson, P.Jagam, J.Law, I.T.Lawson,
  R.W.Ollerhead,

41
The KamLAND Collaboration
P.W.Gorham, J.G.Learned, J.Maricic, S.Matsuno,
S.Pakvasa University of Hawaii S.Dazeley,
S.Hatakeyama,M.Murakami, R.C.Svoboda Louisiana
State University B.D.Dieterle,
M.DiMauro University of New Mexico J.Detwiler,
G.Gratta, K.Ishii, N.Tolich, Y.Uchida Stanford
University M.Batygov, W.Bugg, H.Cohn,
Y.Efremenko, Y.Kamyshkov, A.Kozlov,
Y.Nakamura University of Tennessee L.DeBraeckelee
r, C.R.Gould, H.J.Karwowski, D.M.Markoff,
J.A.Messimore, K.Nakamura, R.M.Rohm, W.Tornow,
A.R.Young Triangle Universities Nuclear
Laboratory Y-F.Wang IHEP, Beijing
K.Eguchi, S.Enomoto, K.Furuno, J.Goldman,
H.Hanada, H.Ikeda, K.Ikeda, K.Inoue, K.Ishihara,
W.Itoh, T.Iwamoto, T.Kawaguchi, T.Kawashima,
H.Kinoshita, Y.Kishimoto, M.Koga, Y.Koseki,
T.Maeda, T.Mitsui, M.Motoki, K.Nakajima,
M.Nakajima, T.Nakajima, H.Ogawa, K.Owada,
T.Sakabe, I.Shimizu, J.Shirai, F.Suekane,
A.Suzuki, K.Tada, O.Tajima, T.Takayama, K.Tamae,
H.Watanabe Tohoku University J.Busenitz,
Z.Djurcic, K.McKinny, D-M.Mei, A.Piepke,
E.Yakushev University of Alabama B.E.Berger,
Y.D.Chan, M.P.Decowski, D.A.Dwyer, S.J.Freedman,
Y.Fu, B.K.Fujikawa, K.M.Heeger, K.T.Lesko,
K.-B.Luk, H.Murayama, D.R.Nygren, C.E.Okada,
A.W.P.Poon, H.M.Steiner, L.A.Winslow UC
Berkeley/ Lawrence Berkeley National
Laboratory G.A.Horton-Smith, R.D.McKeown,
J.Ritter, B.Tipton, P.Vogel California Institute
of Technology C.E.Lane, T.Miletic Drexel
University
42
(No Transcript)
43
SNO Backup Slides
44
Radioactive Backgrounds

• Daughters in U or Th chain
• b decays
• bg decays

Photodisintegration (pd) g d ? n
p Indistinguishable from NC ! Technique ?
Radiochemical assay ? Light isotropy
Cherenkov Tail Cause ? Tail of resolution, or
? Mis-reconstruction Technique ? U/Th calib.
source ? Monte Carlo
Must know U and Th concentration in D2O
45
Radioactive Backgrounds (SNO Phase I)

• I. Ex-situ (Radiochemical Assays)
• Count daughter product decays 224Ra, 226Ra,
  222Rn
• II. In-situ (Low energy physics data)
• Statistical separation of 208Tl and 214Bi using
  light isotropy

46
Low E Background Summary
pd neutron bkg. (counts)
D2O
H2OAV
Atmospheric n
235U spont. fission
2H(a,a)pn
17O(a,n)
Terrestrial reactor n
External neutrons
Total 78 12
For Te? 5 MeV, Rlt550cm
Tail Bkg (counts)
D2O
H2O
AV
PMT
Total
c.f. 2928 n candidates
12 of the number of observed NC neutrons
assuming standard solar model n flux
47
How Will the Salt Be Removed?
48
Data Reduction
Nov 2, 1999 to May 28, 2001 306.4 live days ?
Day 128.5 days, Night 177.9 days
49
Data Reduction Cuts

• Remove instrumental background (e.g. PMT
  flasher using)
• PMT time charge distribution
• Event time correlation
• Veto PMT tag
• Reconstruction information
• Light isotropy arrival timing

Light isotropy measure
Light arrival timing
n signal loss
Residual instrumental bkg. contamination
lt 3 events (95 CL)
50
Event Reconstruction
Given Hit PMTs positions timing
Determine events (x,y,z) (q,f)
Fiducial volume determination (Ntarget?)
Separation of n signals from background
Tools Triggered g and b sources
51
Neutron Calibration
Response vs 252Cf source position

• Calibrate using 252Cf fission source (3.8 n per
  fission)
• Capture Efficiency
• Total 29.90 1.10
• With energy 14.38 0.53
• threshold
• fiducial volume
• selections
• (Tgt5 MeV, Rlt550 cm)

52
CC, ES, NC Flux
53
KamLAND Backup Slides

• KamLAND
• Backup Slides

54
A Candidate Anti-n Event
(colour is time)
Delayed Signal E 2.22 MeV
Prompt Signal E 3.20 MeV
Dt 111 ms DR 34 cm
55
Front End Electronics
Waveforms are recorded using Analogue Transient
Waveform Digitizers (ATWDs), allowing multi p.e.
resolution
ADC Counts
raw data pedestal pedestal subtracted
? The ATWDs are self launching with a threshold
1/3 p.e. ? Each PMT is connected to 2 ATWDs,
reducing deadtime ? Each ATWD has 3 gains (20,
4, 0.5), allowing a dynamic range of 1mV- 1V
samples (1.5ns)
56
Waveform Digitiser
Have full waveform digitizers on every central
and veto channel
1 p.e.
Data from blue LED flashers in the detector
? Important for exploring new physics and reject
complex background signatures
2 p.e.
57
Reactor Anti-Neutrinos
58
Source Spectrum
Goesgen
Standard anti-neutrino spectral determination
procedures checked with short base-line reactor
anti-neutrino experiments
59
Introduction to KamLAND
KamLAND follows the long history of using reactor
anti-neutrinos to investigate neutrino properties

• Spectral distortions if ?e oscillate
• Suppressions factor of 2

Reactor ne spectrum
Cross section for ne p e n
60
Time Variations of Reactor Power and Signals
61
Radioactivity Inside Scintillator
62
Muon-Induced Backgrounds
DL lt 3m
Test energy scale at higher energies.
63
85Kr Background
85Kr coincidence measurement

• Dominant low-energy backgrounds
• 85Kr (Q687 keV)
• 210Pb, 210Bi (from Rn decays)

We are working on purification to remove such
contamination for detector upgrades for 7Be solar
n program
64
Accidental Background
in delayed time window of 0.2-20 s
Epgt2.6 MeV
Accidental bkgd 0.0086 ? 0.0005
65
Vertex Distributions of neutrons 12B/12N
Fiducial Volume Studies
?Vfid/Vfid 4.6
66
Statistical Analysis of Mixing Parameters
Rate-only Analysis
?2 in (Dm2, sin22q) space. Points with ? 2 ?
3.84 (95 CL) are excluded.
SpectralRate Analysis
(Rate)
(Shape)
(Bckgrd)
?2 in (Dm2, sin22q) space. Points with ? 2 ?
5.99 (95 CL) are excluded.
67
General n Background Slides

• General n Backup Slides

68
Remaining Questions

• n Dirac or Majorana
• Absolute n mass scale
• q13
• CP violation in leptonic sector?
• n Mass hierarchy
• Verify oscillation (strong evidence, no direct
  observation yet)
• LSND? Sterile n? CPT violation?

69
Neutrino Mixing
70
Neutrino Mixing What do we know now?
Atmospheric n
Uai
Reactor (CHOOZ)
Solar n LMA
Present thinking Solar ne mix with
71
MNSP vs CKM
Contrast between UCKM (quark) and UMNSP (lepton)
l0.2 and e lt 0.25
What is the underlying symmetry (possibly at GUT
scale)?
72
Future Solar n Experiments
Nakahata (LowNu2002 Conference)