What can we learn about
neutrinos at SNOLAB !?
Alain
Bellerive
Canada Research Chair
Carleton University
www.snolab.ca
Outline
•
•
•
•
•
•
•
•
•
•
Introduction & Neutrino Production in the Sun
Review of Solar Neutrino Experiments
Solar Neutrino Problem
Neutrino Oscillation and Matter Effects
Results from the Sudbury Neutrino Observatory
Constraints on Oscillation Parameters
The Next Phase for SNO
Future Prospects at SNOLAB
A Proposal for Xenon Double Beta Decay Search
Summary and Conclusion
Cornell November 2004
Alain Bellerive
2
Evidence for
Neutrino Oscillations
First evidence of neutrino oscillation

2
e
Atmospheric Neutrinos
high energies
Solar Neutrinos
low energies
Today’s
talk
Today’s talk
!!! !!!
Neutrinos
Proton
beam
Pions
Water
target
Cornell November 2004
e, , and 
e detector
Muons and electrons
Copper beam stop
30 meters
Alain Bellerive
Neutrino Beams
and Reactors
Tunable energies
and distances!
3
Macroscopic Properties of the Sun
Mean Distance from the Earth: 1.5 x 1011m
Mass: 2 x 1030 kg
Radius: 6.96 x 108 m
Luminosity: 3.8 x 1026 W
Neutrino flux: 6.5 x 1010 cm-2 s-1
SNU: Product of solar neutrino fluxes (measured or
calculated) and calculated cross-sections
1 SNU  1 capture per s & per 1036 target atoms
Cornell November 2004
Alain Bellerive
4
Neutrino Production in the Sun
Light Element Fusion Reactions
p + p 2H + e+ + e
99.75 %
p + e- + p  2H + e
0.25 %
3He
+ p 4He + e+ + e ~10-5 %
7Be
+ e- 7Li + e
8B
 8Be* + e+ + e
15 %
0.02 %
Neutrino Production Radius
Chlorine Measurements: Homestake
• 1960’s: 37Cl + e  37Ar + eConstruction of the Chlorine
detector by Ray Davis
• Depth: 4850 ft
• Detector fluid: 3.8 x 105 l of C2Cl4
• Energy Thresold: 0.814 MeV
• 1970 – 1995
Measurements of solar  flux
Sensitive to 8B & 7Be ’s
• Observed rate (SNU)
2.56 ± 0.16(stat) ± 0.16(syst)
• Expected rate (SNU)
7.6 +1.3 [1 from BP2000]
Cleveland et al.,Ap. J. 496, 505(1998)
–1.1
Cornell November 2004
Alain Bellerive
6
Gallium Experiments
71Ga
+ e 
71Ge
+ e-
Energy Threshold: 0.233 MeV
Radiochemical Target
Small proportional counters are
used to count the Germanium
Sensitive to pp, 7Be, 8B, CNO,
and pep ’s
SAGE: Russian-American
Gallium solar neutrino
Experiment (INR RAS)
• GALLEX/GNO:Gallium Neutrino
Observatory in
Gran Sasso
 A liquid metal target which
contains 50 tons of gallium.
 30 tons of natural gallium in an
aqueous acid solution.
Cornell November 2004
Alain Bellerive
7
Gallium Measurements: SAGE (LowNu03)
SAGE overall 1990-2003
+3.7 (syst) SNU
69.6 +4.4
(stat)
-3.2
-4.3
Expected rate [1 from BP2000]
+9 SNU
129 –7
Cornell November 2004
Alain Bellerive
8
Gallium Measurements: GALLEX + GNO
GALLEX
GNO
Expected rate [BP2000]
129 SNU
Neutrino 2002
Water Detector: Super-Kamiokande
•
8B
neutrino measurement by
x + e- → x + e-
• Sensitive to e, , t
(,t + e- )  0.15 x (e + e-)
• High statistics ~15ev./day
• Real time measurement allow
studies on time variations
• Studies energy spectrum
• 50 ktons of pure water with
11,146 PMTs (fiducial volume
of 22.5 ktons for analysis)
Cornell November 2004
Alain Bellerive
10
Solar neutrino data in SK (period I)
May 31, 1996 – July 13, 2001 (1496 days )

e-
qsun
22400230 solar  events
Ee = 5.0 - 20 MeV
8B
flux : 2.35  0.02  0.08 [x 106 /cm2/sec]
Data
SSM(BP2001)
= 0.465 0.005 +0.016
–0.015
Solar  Flux Measurement Results
Chlorine – Gallium – Water experiments
have
different energy threshold
!!! The data suggest an energy dependence !!!
??? What could explain such a variation ???
Cornell November 2004
Alain Bellerive
14
Solar Neutrino Problem
• Historically the first culprit was assumed to be the
method of determining the solar  flux.
• In fact, the last 30 years showed that the SSM provides
and accurate description of the macroscopic properties
of our Sun.
• The mass, radius, shape, luminosity, age, chemical
composition, and photon spectrum of the Sun are
precisely determined and used as input parameters.
• Equation of state relates pressure and density; while
the radiative opacity dictates photon transport.
• Experimental fusion cross sections used to determined
the nuclear reaction rates.
Cornell November 2004
Alain Bellerive
15
Neutrino Mixing:
• As in the quark sector,
it is possible to define
a neutrino mixing
matrix which relates
the mass and weak
eigenstates
Mixing Matrix
 e 
 
   
 
 t 
U e1 U e2 U e 3   1 

  
U 1 U  2 U  3   2 

  
Ut1 Ut 2 Ut 3   3 

Cornell November 2004
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17
Solar Neutrino Oscillations
Pee = sin2(2q) sin2(1.27Dm2 L / E)
• Physics:
Dm2 & sin(2q)
• Experiment:
Distance (L) & Energy (E)
 e 
 
   
 
 t 
U e1 U e2 U e 3   1 

  
U 1 U  2 U  3   2 

  
Ut1 Ut 2 Ut 3   3 
Cornell November 2004
Alain Bellerive
Dm2  Dm122 and q  q12
3 Parameters !
Dm  m  m
q  Mixing angle
2
2
2
2
1
The state evolves with
time or distance
18
Sensitivity to  oscillations
Vacuum Oscillations
MSW Oscillations
• Different types of
experiments sensitive to
different aspects of
oscillation space
• For s in matter can
acquire an effective
mass through
scattering, enhancing
oscillations
102
1
10-2
10-4
10-6
10-8
10-10
Accelerator [~GeV]
Dm2
(eV2 )
Reactor [~MeV]
Atmospheric [~GeV]
Solar [~MeV]
MSW
L/E
(km/GeV)
LP2003
10-2
1
102
104
106
108
1010
MSW = Mikheyev – Smirnov - Wolfenstein
19
Matter-Enhanced Neutrino Oscillations
Neutrinos produced in weak Pee
state e
 High density of electrons in
the Sun
 Superposition of mass states
1, 2, 3 changes through the
MSW resonance effect
 Solar neutrino flux detected
on Earth consists of e + ,t
LP2003
Alain Bellerive
20
Neutrino Oscillations in matter
Neutrino States
Weak States
Mass States
First
1
Second
First
Second
2
e
x

Time Evolution

Δm 2
Δm 2
  q  cos2θ
sin2θ 
d  e  1 eee   cos
cos
qsinsin


q
q
1



4E1  
4E 2
i    T      

2     
T
2
2




Δm
Δm
q2 
dt  x  2 xx   sin

sin
q
cos
Δm
Δm


q
cos
q
cos2θ
sin2θ
  2 sin2θ
2G F N e
 e   x  
d  e 
cos2θ

4E
i    H  
4E

T   4E  2 4E
2
dt  x  Purexx 
Δmx
x


Pure Δm
Pure

sin2θ
cos2θ 
 2 2

4E
4E

x x sinsin
2
q q
q 2q
coscos
Time Evolution
2
1 1
1
0
LP2003

sin 2qe e
2
sin 2q m  q q
2
2
(


cos
2
q
)

sin
2q

q q
2
   2GF N
E
/
D
m
e
Time
Alain Bellerive
21
Mixing
Parameters
SMA
Combination of the
Chlorine, Gallium,
SK, and CHOOZ
restricted the mixing
parameters
Dm2 (eV2)
LMA
LOW
VAC
Pre SNO
Allowed Regions
Phys.Rev. D64 (2001) 093007
Cornell November 2004
Alain Bellerive
JustSo2
tan2q
22
Subury Neutrino Observatory
• Timeline
• Experimental Apparatus
• First Results from the D20 Phase
• Most Recent Results from the Salt
Phase
• Outlook to the NCD Phase
OVERAL PICTURE
Cornell November 2004
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23
SNO Timeline
1999
Commissioning
2000
D 2O
2001
2002
D2O + Salt
2003
2004
D2O
1998
2005
2006
D2O + 3He counters
3He
counters: Install &
Commission
• Phase 1: D2O
• Phase 2: D2O + Salt (NaCl)
• Phase 1a: D2O
• Phase 3: D2O + 3He counters
Cornell November 2004
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24
Underground laboratory in Sudbury
SNOLAB
Cornell November 2004
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25
Sudbury Neutrino Observatory
2092 m to Surface (6010 m w.e.)
PMT Support Structure, 17.8 m
9456 20 cm PMTs
~55% coverage within 7 m
Acrylic Vessel, 12 m diameter
1000 tonnes D2O
1700 tonnes H2O, Inner Shield
5300 tonnes H2O, Outer Shield
Urylon Liner and Radon Seal
Energy Threshold = 5.511 MeV
Cornell November 2004
Alain Bellerive
26
Purpose of SNO
• If Solar Neutrino Problem due to νe
oscillation
flavour
mixing to νμ and/or ντ , SNO should
provide direct evidence .
• SNO measures flux of νe and flux of
(νe+νμ+ντ).
• Previous expt’s sensitive to only νe or
mainly νe.
Water Čerenkov expt’s:
Kamiokande, Super-K
Cornell November 2004
Radiochemical expt’s:
37Cl at Homestake and
71Ga at Gran Sasso/Baksan
Alain Bellerive
27
Neutrino detection in SNO
• PMTs detect
Čerenkov photons
from relativistic e-:
e-
– e- from CC or ES
43o
reaction
– γ from n-capture
(NC reaction)
usually Comptonscatters e- (pair
production less
likely).
Cornell November 2004
Čerenkov cone
Alain Bellerive
28
Neutrino detection in SNO
• Hit pattern from
Čerenkov cone
indicates physics
event.
• PMT hit times and
locations used to
reconstruct edirection and
location
• Number of PMT hits
used to estimate
electron energy.
Cornell November 2004
Alain Bellerive
29
SNO observables - event by event
PMT Information: Positions, Charges, Times
Event Reconstruction
Vertex, Direction, Energy, Isotropy
Cornell November 2004
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30
Cornell November 2004
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31
Neutrino Reactions in SNO
CC
e  d  p  p  e−
Produces Cherenkov
Light Cone in D2O
- Q = 1.445 MeV
- good measurement of e energy spectrum
- some directional info  (1 – 1/3 cosq)
- e only
NC
 x  d  p  n  x
n captures on deuteron
2H or 35Cl or 3He
- Q = 2.22 MeV
- measures total 8B  flux from the Sun
- equal cross section for all  types
ES
 x  e−   x  e−
Produces Cherenkov
Light Cone in D2O
- low statistics
- mainly sensitive to e, some  and t
- strong directional sensitivity
Cornell November 2004
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32
An Ultraclean Environment
• Highly sensitive to
any g above neutral
current (2.2 MeV)
threshold.
Uranium
Thorium
3.27 MeV b
2.615 MeV g
• Sensitive to 238U
& 232Th decay chains
Cornell November 2004
Alain Bellerive
33
Three Ways to Catch Neutrons!
(NC)  x  d   x  p  n
Pure D2O
Salt
3He
Nov. 99 - May 01
July 01 - Sep. 03
Summer 04 - Dec. 06
n captures on
deuterium
σ = 0.0005b
6.2 MeV γ
n captures on chlorine
σ = 44b
8.6 MeV multiple γ’s
n captures on 3He
in discrete prop.
counter array
σ = 5330b
0.764 MeV γ
n
γ
γ
γ
γ
n
3H*
2H
PRL 87, 071301, 2001
PRL 89, 011301, 2002
PRL 89, 011302, 2002
Cornell November 2004
3H
5 cm
n
36Cl*
35Cl
36Cl
PRL 92, 181301, 2004
Alain Bellerive
3H
p
3He
n + 3He  p + 3H
34
Subury Neutrino Observatory
D2O Results
Cornell November 2004
Alain Bellerive
35
#EVENTS
Shape Constrained Signal Extraction Results
CC 1967.7 +61.9
+60.9
ES
NC
Cornell November 2004
263.6
+26.4
+25.6
576.5
+49.5
+48.9
Alain Bellerive
36
Shape Constrained Neutrino Fluxes
Signal Extraction in FCC,
FNC, FES with
E > 5.511 MeV
Fcc(e) =
+0.06
+0.09
1.76 -0.05 (stat.) -0.09 (syst.)
x106 cm-2s-1
Fes(x) =
+0.24
+0.12
2.39 -0.23 (stat.) -0.12 (syst.)
x106 cm-2s-1
Fnc(x) =
+0.44
5.09 -0.43
x106 cm-2s-1
+0.46
(stat.) -0.43 (syst.)
Signal Extraction in Fe,
FeF=cc(e)
+0.05
1.76 -0.05
=
FtF=es(x)
Ft
+0.09
(stat.)
-0.09 (syst.)
and
6 cm-2s-1
x10
Fnc(x) = Fe + Ft
Fe
 Fe
6 cm-2s-1
 Ft x10
with
0.15
+0.45
+0.48
3.41 -0.45
(stat.)
= (1) -0.45+(syst.)
Cornell November 2004
Alain Bellerive
37
SNO NC in D2O (April 2002)
~ 2/3 of initial solar e are observed at SNO to be ,t
Flavor change
at 5.3  level.
Sum of all the
fluxes agrees
with SSM.
FSSM = 5.05 -+1.01
0.81
106 cm-2 s-1
+0.46
FSNO = 5.09+0.44
-0.43 -0.43
106 cm-2 s-1
Phys. Rev. Lett. 89 (2002)
Cornell November 2004
Alain Bellerive
38
The Solar Neutrino Problem
Experiment
Exp/SSM
•SAGE+GALLEX/GNO
0.55
•Homestake
0.34
•Kamiokande+SuperK
0.47
•SNO CC (June 2001)
0.35
SNO NC (April 2002)
1.01
SNO CC vs NC implies flavor change, which can
then explain other experimental results.
Cornell November 2004
Alain Bellerive
39
Day/Night Asymmetries
AX 
(F night  F day )
(F night  F day ) / 2
Signal Extraction for FCC, FNC, FES  Fe and FTOT
Allowing Atot  0
ATOT = -24.2 ± 16.1 +2.4
%
- 2.5
Ae = 12.8 ± 6.2+1.5 %
-1.4
Night - Day
With constraint Atot = 0
+1.3
Ae = 7.0 ± 4.9 - 1.2 %
Cornell November 2004
Alain Bellerive
40
SNO: Constraint on mixing parameters
Day/Night
and
Energy Spectra
SNO Alone
Allowed Regions
Cornell November 2004
Alain Bellerive
41
Progress in 2002
on the Solar
Neutrino Problem
March 2002
April 2002
with SNO
Dec 2002
with KamLAND
Subury Neutrino Observatory
Salt Results
Cornell November 2004
Alain Bellerive
43
Advantages of Salt (original idea from Carleton)
 Neutrons capturing on 35Cl
provide higher neutron
energy above threshold.
 Higher capture efficiency
 Gamma cascade changes the
angular profile.
g
n
35Cl
36Cl*
Cornell November 2004
36Cl
Alain Bellerive
44
Advantages of salt: n-detection efficiency
With salt, higher E
release from ncapture and higher σ
for n-capture mean
much higher NC
detection efficiency.
Cornell November 2004
Alain Bellerive
45
isotropic
Event
vertex
θij
Isotropy variable, β14 , function
of angles between each pair
of hit PMTs (θij) in event.
(similar to thrust in collider physics)
Cornell November 2004
Alain Bellerive
not isotropic
Advantages of salt: event isotropy
isotropy β14
β14 powerful discriminating
variable between NC and
CC/ES events. .
46
Calibration of detector
Red – Data
Blue – MC
(neutron) and 16N (6 MeV γ)
sources provide check of MC for β14
252Cf
Cornell November 2004
Alain Bellerive
triggered γ -ray source
calibrates energy response
16N
47
D2O + Salt analysis: data set and
data reduction
435,721,068 triggers
• Data recorded from July
2001 to October 2002
(2/3 of D2O + salt data).
• 254.2 live days (detector
maintenance and
calibration during
remaining time).
Instrumental
background cuts
Cosmic ray muons +
spallation products
Vtx reconstruction, PMT time
and position disributions
• Blind analysis performed
– Analysis and cuts tuned
with MC and “spoiled”
subset of data.
Cornell November 2004
Radius ≤ 550 cm, T ≥ 5.5 MeV
3055 events
Alain Bellerive
48
Radioactive backgrounds
• Ex situ measurements
show U and Th levels
lower than goals (1
background neutron/day).
• Ex situ measurements
consistent with in situ
measurements
• In situ measurements
more precise so used for
solar neutrino analysis.
Cornell November 2004
Alain Bellerive
49
Backgrounds
U and Th
Recall:
3055
candidate
events
Cornell November 2004
Alain Bellerive
50
Measurement of CC, NC, ES events
• MC PDFs compared to data; extended unbinned
ML fit used to estimate free parameters in fit.
• 3 (or 4) variables used to calculate likelihood
PDFs:
–
–
–
–
Radial position of reconstructed vertex
Direction of electron w.r.t. Sun, cos θsun
Event isotropy, β14 (PMT hit pattern)
Electron kinetic energy (PMT hits) (optional)
• Free parameters in fit:
– number of NC, CC, ES signal events
– “external neutron” background events
Cornell November 2004
Alain Bellerive
Matter enhanced oscillations
change ES and CC spectra
51
PDFs for signals and backgrounds
Isotropy
Radius of fitted vertex
β14
Cornell November 2004
Alain Bellerive
(Rfit/6 m)3
52
PDFs for signals and backgrounds
To Sun
Away from Sun
Sun-electron direction
cos θsun
Cornell November 2004
Alain Bellerive
Electron kinetic energy
Teff (MeV)
53
Flux results from fit
Units for  are 106 cm-2 s-1
Energy spectrum
of 8B ν’s constrained
to Ortiz, et al. spectrum
Energy spectrum
of 8B ’s unconstrained
(Energy not used in fit)
Standard Solar Model
(Bahcall, Pinsonneault 2004)
Cornell November 2004
BP04 = 5.82 ± 1.34
Alain Bellerive
54
Systematic uncertainties
Cornell November 2004
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55
Comparison to previous results and
SSM (BP2000)
More precise
salt results
confirm
D2O results.
Cornell November 2004
Alain Bellerive
56
Interpretation of salt flux results:
neutrino oscillation parameters
SNO data only
Ratio of CC/NC fluxes gives P(νe → νe)
P(νe → νe) = 1- sin2(2θ)sin2(1.27Δm2L/E)
Cornell November 2004
Alain Bellerive
57
Interpretation of salt flux results:
neutrino oscillation parameters
1-D projections of oscillation
parameters give marginal
uncertainties on tan2θ and
Δm2.
θ = 32.5+1.7-1.6 degrees
Maximal mixing (θ = 45 degrees)
excluded at 5.4 σ.
Δm2 = (7.1+1.0-0.3) x 10-5 eV2
Cornell November 2004
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58
Salt Removal: D2O Optics Restored
~1.2%
16N
Nhit drop when salt was
added to SNO
 Reverse osmosis a success
 Optical properties restored
after the salt phase!
Energy (MeV)
 Understand why the mean
~2.0%
Cornell November 2004
Alain Bellerive
59
Subury Neutrino Observatory
NCD Phase
Cornell November 2004
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60
NCD Deployment
Cornell November 2004
Alain Bellerive
61
SNO NCD Phase
NC
Neutral Current Detectors
 x  d  p  n  x
n  3He  p  t
νx
• Event by event separation
• Break the correlation between
NC & CC events
• Measure in separate data
streams NC & CC events
• Different systematic errors
than neutron capture on NaCl
n
• Commissioning Fall 04 (now!)
Cornell November 2004
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62
Optical Calibration: LIVE !!!!!
Cornell November 2004
Alain Bellerive
63
NCD Phase - Advantage of 3He counters
Correlation Coefficient
CC,NC
NC,ES
CC,ES
D2O
Salt
3He
-0.950
-0.297
-0.208
-0.521
-0.064
-0.156
~0
~0
~ -0.2
 Reduction in anti-correlation between NC and CC will help
to reduce uncertainty in CC/NC ratio.
 Smaller uncertainty in CC/NC ratio means smaller
uncertainty in tan2θ.
 Best CC spectrum from D2O with NC constrained by NCD
and overall consistency with Salt
Cornell November 2004
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64
What SNO might tell us in the future…
The Ultimate D2o + Salt + NCD Analysis !
Salt phase 254 day results provide independent measurement of 8B solar
neutrino flux, demonstrate flavor conversion to >7σ, and improve MSW
parameter measurements.
Goal for Final SNO
Current Oscillation Picture:
(D2O + salt + NCD)
Results from full 391
days of salt data soon!
Includes day-night and
spectrum.
3He
phase underway,
for event-by-event NC
discrimination…and
even better physics!
CC/NC ratio to 7%
D/N asymmetry to
3% abs. uncertainty
hep-ph/0406328
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SNOLAB
EXO
A Proposal for Double
Beta Decay Search
• Absolute Majorana Neutrino Mass Scale
• Why Xenon?
• Prototype at WIMP
• Time Projection Chamber R&D
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There are two varieties of ββ decay
2ν mode: a conventional
2nd order process
in nuclear physics
0ν mode: a hypothetical
process can happen
helicity
only if: Mν ≠ 0 Since
has to “flip”
ν=ν
Several new particles can take
the place of the virtual ν
But 0νββ decay always implies new physics
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Effective Majorana ν mass
(εi = ±1 if CP is conserved)
m 
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2
U
 e,i mi  i
i 1
71
Xe is ideal for a large experiment
•No need to grow crystals
•Can be re-purified during the experiment
•No long lived Xe isotopes to activate
•Can be easily transferred from one detector to
another if new technologies become available
•Noble gas: easy(er) to purify
•136Xe enrichment easier and safer:
- noble gas (no chemistry involved)
- centrifuge feed rate in gram/s, all mass useful
- centrifuge efficiency ~ Δm. For Xe 4.7 amu
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Background due to the Standard Model 2bb decay
2bb spectrum
(normalized to 1)
0bb peak (5% FWHM)
(normalized to 10-6)
0bb peak (5%
FWHM)
(normalized to 10-2)
Summed electron energy in units of the kinematic endpoint (Q)
from S.R. Elliott and P. Vogel, Ann.Rev.Nucl.Part.Sci. 52 (2002) 115.
The only effective tool here is energy resolution
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Electrostatic analysis looking at field uniformity
TPC Simulation
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R&D Effort
TPC
 New Initiative at Carleton
 Time Projection Chamber
 Application for EXO
 Overlap with detector
development for the ILC
 World consensus to build a
new e+ e- linear collider (LC)
 Detectors capable of precision
measurements
Track reconstruction
with charge dispersion
on resistive anode and
resolution study
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Conclusion
• SNO provided direct evidence of flavor conversion
of solar e’s
• SNO (d2o+salt+ncd) will provide the ultimate
measurment of the total (NC) solar x flux
• Real-time data do not show large energy distortion
nor time-like asymmetry
• Matter Effect explains the energy dependence of
solar oscillation
• Large mixing angle (LMA) solutions are favored
• Solar Neutrino Problem is now an industry for
precise measurements of neutrino oscillation
parameters – SNO (d2o+salt+NCD) Ultimate NC
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Implications and Outlook
Solar neutrinos demonstrate that neutrinos have mass
and the minimum SM is incomplete
– Unlike the quark sector where the CKM mixing angles are small,
the lepton sector exhibits large mixing
– The  masses and mixing may play significant roles in
determining structure formation in the early universe as well as
supernovae dynamics and the creation of matter
The coming decade will be exciting for neutrino physics
helping delineate the New Standard Model that will
include neutrino masses and mixing
– Precision measurements of the leptonic mixing
matrix
– Determination of neutrino masses (e.g. EXO)
– Investigation of lepton sector CP and CPT properties
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A (probably incomplete) list of the different ideas discussed
by various groups
Experiment
Nucleus
Detector
CUORE
130Te
.77 t of TeO2 bolometers (nat)
7 x 1026
.014-.091
EXO
136Xe
10 t Xe TPC + Ba tagging
1 x 1028
.013-.037
GENIUS
76Ge
1 t Ge diodes in LN
1 x 1028
.013-.050
Majorana
76Ge
1 t Ge diodes
4 x 1027
.021-.070
MOON
100Mo
34 t nat.Mo sheets/plastic sc.
1 x 1027
.014-.057
DCBA
150Nd
20 kg Nd-tracking
2 x 1025
.035-.055
CAMEO
116Cd
1 t CdWO4 in liquid scintillator > 1026
.053-.24
COBRA
116Cd ,
10 kg of CdTe semiconductors
1 x 1024
.5-2.
Candles
48Ca
Tons of CaF2 in liq. scint.
1 x 1026
.15-.26
GSO
116Cd
2 t Gd2SiO5:Ce scint in liq scint
2 x 1026
.038-.172
Xmass
136Xe
1 t of liquid Xe
3 x 1026
.086-.252
130Te
T0ν (y)
< mν > eV
Note that the sensitivity numbers are somewhat arbitrary, as they depend
on the author’s guesstimate of the background levels they will achieve
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Xe offers a qualitatively new tool against background:
136Xe
136Ba++ e- e- final state can be identified
using optical spectroscopy (M.Moe PRC44 (1991) 931)
Ba+ system best studied
(Neuhauser, Hohenstatt,
Toshek, Dehmelt 1980)
Very specific signature
“shelving”
Single ions can be detected
from a photon rate of 107/s
2P
1/2
650nm
493nm
•Important additional
constraint
•Huge background
reduction
Cornell November 2004
4D
2S
metastable 47s
3/2
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