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Title: PITP, Vancouver, October 17, 2008


1
Subterranean Answers to some very Deep
Questions
PITP, Vancouver, October 17, 2008 Art
McDonald Queens University, Kingston, Ontario
2
  • A list of the deepest questions in physics would
    certainly include
  • How do neutrinos fit into the Standard Model of
    Elementary Particles?
  • Do they have a finite mass?
  • Do they change from one type to another?
  • Are the present detailed models of the Sun
    correct?
  • What is the Dark Matter that is known to make up
    about
  • 23 of the mass of our Universe?
  • How did we end up with a matter-dominated
    Universe when it appears that there was almost an
    equal amount of anti-matter made in the Big Bang?

3
  • By going 2 km underground and creating an
    ultra-low radioactivity environment in the
    Sudbury Neutrino Observatory and the new SNOLAB,
    we have answered some of these questions and are
    poised to address the others over the next few
    years.
  • The experiments to do this and the very deep
    questions that motivate them will be the subject
    of this lecture.

4
To study Neutrinos with little radioactive
background, we went 2 km underground to reduce
cosmic rays and built an ultra-clean laboratory
CVRD-INCOS CREIGHTON MINE NEAR SUDBURY, ONTARIO
About 1.25 Whistlers Deep
Nickel ore
5
We are apparently not the first to think of doing
science underground
6
However, we are presently the deepest by a
substantial margin.
A significant advantage in reducing cosmic ray
background.
7
Properties of Neutrinos
  • Neutrinos, along with electrons and quarks are
    basic particles of nature that we do not know how
    to sub-divide further. They come in three types
    (electron, mu, tau) as described in The Standard
    Model of Elementary Particles, a very successful
    theory for microscopic particles. This basic
    theory postulated that they had no mass and did
    not change from one type to another.

8
(No Transcript)
9
Properties of Neutrinos
  • Neutrinos have no electric charge and do not
    feel the Strong Force. Therefore, Neutrinos only
    stop if they hit the nucleus of an atom or an
    electron head-on, so matter is open space for
    them. They can pass through a million billion
    kilometers of lead without stopping. Therefore
    they are very difficult to detect and far less is
    known about them than the other basic particles.

10
In 1984, when we started to work on the Sudbury
Neutrino Observatory, our main objective was to
solve
  • THE SOLAR NEUTRINO PROBLEM
  • The nuclear reactions which power the sun make
    enormous numbers of neutrinos.
  • However, all neutrino measurements for 30 years
    before SNO observed too few of the electron type
    neutrinos produced in the sun compared to solar
    models that predict other solar properties well.
  • Either
  • 1. We do not understand the energy generation
    processes in the sun
  • Or
  • 2.The electron neutrinos created in the sun are
    changing to another type and thereby eluding the
    past experiments. (New physics beyond the
    Standard Model)

11
Nuclear Reactions Powering the Sun
Many neutrinos emitted over a range of energies
12
Detailed models of the Sun by John Bahcall and
others provided very good predictions for solar
properties (luminosity, radius) and predicted
neutrino fluxes in detail.
Experiment Thresholds
, SNO
13
Experiments sensitive primarily or exclusively to
Electron Neutrinos saw too few neutrinos
compared to Solar Models
Solar Neutrino Problem
1967 - 2001
SNOs heavy water is designed to search for
direct evidence of flavor transformation for
neutrinos from 8B decay in the Sun. Both
electron neutrinos and all 3 active neutrino
types are measured to exhibit the appearance of
other neutrino types.
14
Neutrino Detection in SNO Heavy Water (D2O)
(1 in 7000 natural water molecules are D2O rather
than H2O)
By comparing these two reactions, it is possible
to determine whether the neutrinos reaching the
Earth are all still electron neutrinos.
15
Sudbury Neutrino Observatory
1000 tonnes of heavy water D2O 330 million
on Loan for 1.00
34 m or Ten Stories High!
9500 light sensors
12 m Diameter Acrylic Container
Ultra-pure Water H2O.
Urylon Liner and Radon Seal
The whole laboratory is maintained as a clean
room to avoid mine dust contamination
16
SNO One million pieces transported down in the
9 ft x 12 ft x 9 ft mine cage and re-assembled
under ultra-clean conditions. Every worker takes
a shower and wears clean, lint-free clothing.
Over 70,000 Showers to date and counting
17
An Ultra Clean Laboratory Class 2000 everywhere.
Cleaner than a hospital operating room yet
located in a very active mining environment.
18
Measure Position, Direction, Energy Of
a Neutrino Event Discriminate Against Backgroun
d Radioactivity
Cerenkov Light Detection in SNO
Actual Data from the Monitoring Computer
19
SNO 3 neutron detection methods for nall
reaction.
Phase I (D2O) Nov. 99 - May 01
Phase II (salt) July 01 - Sep. 03
Phase III (3He) Nov. 04-Dec. 06
Remove salt, add 400 m of proportional counters 5
cm diameter. Neutron Effc. 30
n captures on deuterium Effciency 14.4 nall
and ne Separation difficult
Add 2 tons NaCl n captures on chlorine Effc.
40 nall and ne separation by event isotropy
Measure nall rate with Independent system. Paper
in June 2008.
Measure Total Flux of all Neutrino types (nall),
Compare with solar models.
Final ne / nall ratio Measured to lt 7
Demonstrate Neutrino Flavor Change clearly
20
SNO Phase 2 data 391 live days with salt
hep-ex/0502021 March 2005
Total Spectrum
Blind analysis of data
Sum fit
nall
ne
Measured background of U, Th fewer than 1 decay/
ton of D2O per day
21
SNO Phase 2 with salt
EVENTS VS VOLUME Bkg lt 10
ISOTROPY NC, CC separation
nall
ne
nall
ne
Heavy water
ENERGY SPECTRUM FROM ne REACTION
DIRECTION FROM SUN
NO OBSERVABLE DISTORTION
Neutrino electron elastic scattering
22
LESS THAN ONE CHANCE IN 10 MILLION FOR NO
CHANGE IN NEUTRINO TYPE
SOLAR MODEL
Excellent Agreement With the Solar Model
Solar Neutrino Problem Solved
Standard Model For Elementary Particles must be
modified
ELECTRONNEUTRINOS
ALL NEUTRINO TYPES
A CLEAR DEMONSTRATION OF NEUTRINO FLAVOR
CHANGE INDEPENDENT OF SOLAR MODELS 2/3 OF THE
ELECTRON NEUTRINOS HAVE CHANGED TO MU,
TAU NEUTRINOS ON THE WAY FROM THE SOLAR CORE TO
EARTH
23
Phase 3 400 m of Neutron Counters installed in
the heavy water by a remotely controlled submarine
Light Sensors
Neutron Detectors
The original Submarine
Yellow, of course!
The yellow paint was much too radioactive.
Well, maybe not!
24
Phase 3 Neutrons from solar neutrino interactions
Phys. Rev. Lett. 101,111301 (2008).
NC Signal 983 77 Neutron background 185
25 Alphas and Instrumentals 6126 250 (0.4 to
1.4 MeV)
Confirms previous SNO results with improved
overall accuracy
One background count per 2 hours in 400 meters of
detectors.
25
What about Neutrino Mass? Flavor Change for
Massive Neutrinos
For simplicity, consider only two neutrino
flavors Suppose the flavor eigenstates,
are not the mass eigenstates,
Then the flavor eigenstates can be represented
as a superposition of the mass eigenstates

where q is a mixing
angle. The time evolution of the flavor states
becomes Writing this in terms of m1,m2, and
the flavor states

where E is the energy

and The survival probability of an
electron neutrino that has traveled a distance L
in a vacuum is then

exhibiting oscillation with L.
26
Matter Effects the MSW effect
(Mikheyev, Smirnov, Wolfenstein)
The extra term arises in dense matter because ne
have an extra interaction via W exchange with
electrons in the Sun or Earth.
In the oscillation formula
Detailed fits to solar neutrino data indicate
that electron neutrinos interact with electrons
in the sun so that they emerge as a mass 2 state
with nearly equal parts electron, mu, tau and do
not change from that in transit to Earth.
27
2008
2003 Kamland (Japan) reactor anti-neutrinos
observed to disappear over 180 km travel
distance. This gives parameters that overlap the
solar ones Strong confirmation of the parameters
for flavor change with massive neutrinos.
The model of flavor change with finite mass
neutrinos is the only one that works for all the
data to date, so other postulates for flavor
change are at most secondary effects. This also
implies that the Standard Model must be extended
to include massive neutrinos. Models for
including neutrino mass are numerous, but many
have already been excluded by the precision of
the measurements to date. We have also confirmed
the validity of solar model calculations to high
accuracy. Well done John Bahcall et al.
28
Solar KamLAND fit results
eV2
m2 gt m1 known from MSW effect
degrees (SNO June 2008)
deg (previous)
Neutrino flavour symmetry phenomenology
(Smirnov summary at Neutrino 2008) Tri-Bi-Maxima
l Mixing 35.2 deg Quark-Lepton Complementarity
32.2 deg (q12 qCabbibo 45 deg)
29
Other Neutrino fluxes at the Earth
30
Atmospheric Neutrinos (SuperKamiokande data,
first observations 1998)Japanese underground
laboratory
  • cosmic rays hit atmosphere
  • pgmnm mgnmnee
  • nm2ne
  • look at zenith angle distribution

Disappearance of atmospheric muon neutrinos
  • q23 large and Dm2322x10-3

Confirmed by accelerator experiments
31
Using the oscillation framework
For 3 Active neutrinos. (MiniBoone has recently
ruled out LSND result)
Maki-Nakagawa-Sakata-Pontecorvo matrix
(Double b decay only)
?
?
?
Solar,Reactor
Atmospheric
CP Violating Phase
Reactor, Accel.
Majorana Phases
Range defined for Dm12, Dm23
For two neutrino oscillation in a vacuum (valid
approximation in many cases)
32
Neutrino Properties Now known
For comparison melectron 500,000 eV
m3 m2 - 0.05 eV
m2 m1 0.009 eV
Mass of lightest neutrino lt 2.2 eV From tritium
beta decay expts.
Neutrino Properties from future experiments
  • Does neutrino flavor change involve a
    matter/anti-matter asymmetry known as CP
    violation? (First observed by Fitch and Cronin
    for quarks)
  • If so, there could be a theoretical explanation
    for the anti-matter disappearance in the early
    Universe.
  • Experiments1. Long baseline flavor change (T2K)
  • 2. Double Beta Decay (SNO)


These involve the neutrino parameters above CP
33
BIG BANG
Evolution Of the Universe
  • Next Questions
  • Total neutrino mass
  • Where has all the
  • Anti-matter gone?
  • Clues from
  • Neutrino properties?

The Sun, Supernova
The Atomic Elements from which we are formed are
made in Stars (such as our Sun) and Supernovae
34
Neutrinoless Double b Decay
Double Beta Decay
Some Nuclei can decay by emitting two electrons
and two anti-neutrinos. For example
  • Requires
  • Neutrino Anti-neutrino
  • (Majorana particles)
  • Finite n mass
  • Lifetimes gt 1026 years
  • Imply n mass lt 0.1 eV

Neutrinoless
Summed Electron Energy
Others 136Xe , 130Te, 76Ge
35
Measuring Effective n Mass
mnbb ?i Uei ² mi
T1/2 F(Qbb,Z) M0n2 ltmnbbgt2
mnbb m1 cos2q13cos²?12 m2 e2i?
cos2q13sin²?12 m3 e2i? sin²?13
Mass Hierarchies
Present Expts.
Inverted
Degenerate
0.04 eV
Normal
normal hierarchy
inverted hierarchy
Normal
Inverted
Want sensitivity lt 0.04 eV large mass/low
background
a,b relevant for matter/anti-matter Asymmetry in
early Universe
36
Neutrino-less Double Beta Decay in SNO..SNO
  • Replace the heavy water with Liquid
    Scintillator (an organic material giving more
    than 40 times more light output)
  • Add about 1 ton of an organic compound of Nd
    more than 2 x 1026 atoms of 150Nd without
    affecting the light collection properties. We
    also have prospects of up to 10 times as much
    150Nd through laser-based isotope separation
    techniques 2 x 1027 atoms of 150Nd.
  • When the two electrons are emitted, they make
    light by ionizing the liquid scintillator. We
    collect the light with the SNO light sensors and
    look for the peak from neutrino-less double beta
    decay.
  • With a few years of counting we could be
    sensitive at an effective mass of 0.04 eV,
    corresponding to the larger of the mass
    differences defined by neutrino oscillations m3
    m2.

37
Main Engineering Change for SNO
The organic liquid is lighter than water so the
Acrylic Vessel must be held down.
Existing AV Support Ropes
AV Hold Down Ropes
Otherwise, the existing detector, electronics
etc. are unchanged.
38
SNO (150Nd Neutrino-less Double Beta Decay)
  • 0n 1057 events per
  • year with 500 kg
  • 150Nd-loaded liquid
  • scintillator in SNO.
  • Simulation
  • assuming light
  • output and background
  • similar to Kamland.

One year of data mn 0.15 eV
U Chain
Th Chain
Sensitivity after three years 1 Ton Natural Nd
(56 kg 150Nd) mnbb 0.1 eV 500 kg
enriched 150Nd mnbb 0.04 eV
39
SNOLAB
Phase II Cryopit
70 to 800 times lower m fluxes than Gran Sasso,
Kamioka.
Cube Hall
Excavation complete. Fully clean and useable by
the end of 2008.
Ladder Labs
Utility Area
SNO Cavern
Personnel facilities
All Lab Air Class lt 2000
40
Cube Hall
41
Personnel Facility
42
BIG BANG
Evolution Of the Universe
Composition of The Universe There appear to be
a lot of particles unlike anything we
have observed on Earth to date. Dark
Matter Particles.
43
Composition of the Universe as we understand it
in 2008 (Very different than 20 years ago thanks
to very sensitive astronomical and astrophysical
experiments such as measurements of the cosmic
microwave background, large scale structure and
distant supernovae.)
Responsible for accelerating the Universes
expansion
Neutrinos Are only a few
With SNOLAB we can look for Dark Matter particles
left from the Big Bang, with ultra-low
radioactive background.
44
Dark Matter
  • Fritz Zwicky (1933) Found that
  • coma galaxy cluster had too little
  • visible mass to account for the
  • distribution of rotational velocities
  • Vera Rubin (1970) Detailed study of orbital
    rotation
  • in galaxies and similar flat rotation curves,
    suggesting
  • dark matter accounted for up to 10 times mass of
    visible
  • Matter in galaxies.
  • Much detailed data now overwhelmingly confirm
  • existence of dark matter
  • Rotational speeds in galaxies and clusters
  • Gravitation lensing
  • Structure formation and cosmology
  • (anisotropy of the cosmic microwave
    background)

45
Supersymmetry (SUSY) 1973-?
  • Introduces a new symmetry and new super-partner
    particles
  • New particle properties (Lightest Supersymmetric
    Particle) could well be consistent with those
    needed to account for the missing dark matter
  • So SUSY could provide a particle physics solution
    to a cosmological problem new particle is
    generically a WIMP
  • We can look for these new particles
  • By producing and detecting them at
  • accelerators (LHC at CERN will be
  • on-line in 2008)
  • Indirectly, by their annihilation in Earth,
  • Sun, galaxy
  • or directly by their elastic scattering
  • from target nuclei

LHC tunnel at CERN
46
DARK MATTER Detection with Liquid Argon
DEAP/CLEAN
  • Scintillation time is much longer
  • for ionization than nuclear recoils
  • for Ar. This enables WIMP recoils
  • to be separated from gammas.
  • Main challenge is background from
  • radioactive 3 9Ar in natural Ar (1/sec/kg)
  • Galbiati, Calaprice Identified argon low
  • in 39Ar (x 20) from underground sources.

M.G. Boulay A. Hime, astro-ph/0411358
47
Dark Matter detection with liquid Argon
DEAP/CLEAN
Very simple concept made possible by detecting
light only Acrylic vessel containing Ar,
surrounded by PMTs (sound familiar?) Program
DEAP-1 (7Kg) now operating Underground Mini-Clean
(2009) 360kg (100 kg fiducial) DEAP/CLEAN
(2011) 3600 kg (1000 kg fiducial)
Ar
Tests of discrimination with DEAP-1
DEAP/CLEAN Good light collection for 3600 kg
Ar. Gamma discrimination proven to gt1.6 x
107. Projected to be gt109 discrimination for the
full scale detector. Less than 1 background event
per year. Light detection from Liquid Argon
should improve sensitivity for WIMP detection by
10 to 100 times in the next few years compared to
present limits.
48
Cube Hall
10T Monorail
Universal Interface and Device Insertion
Gantry Cranes
Assembly Clean Room
MiniCLEAN Shield Tank
DEAP/CLEAN Process Systems
DEAP/CLEAN Shield Tank
49
Super CDMS 25 kg
CDMS-II 50 kg-days
(Ge) XENON-10 300 kg-days
(Xe) DEAP/CLEAN 1,000,000 kg-days (Ar)
3600 (3 yrs)
50
PICASSO THE WIMPS MAKE DROPLETS IN A SUPERHEATED
GEL
Fluorine is very sensitive for the spin-dependent
interaction
ACOUSTIC SIGNAL
Montreal,Queens, Indiana, Pisa, BTI
51
Super-Symmetric Theory predictions For
spin-dependent Interactions are lower Than 10-3
pb, Accessible by future Versions of PICASSO.
52
New large scale project.
2009MiniCLEAN 360, DEAP/CLEAN 3600 Dark Matter
SNOLAB
Phase II Cryopit
2009 HALO Supernova
70 to 800 times lower m fluxes than Gran Sasso,
Kamioka.
Cube Hall
2010 SuperCDMS? Dark Matter
2010 PICASSO IIB? Dark Matter 2010 EXO-200-Gas?
Double Beta
NowPICASSO-II Dark matter
NowDEAP-1 Dark metter
Ladder Labs
Utility Area
2010 SNO Double Beta Supernova Solar neutrinos
SNO Cavern
Personnel facilities
All Lab Air Class lt 2000
53
CONCLUSIONS
  • We are making tremendous progress in
    understanding our Universe and its evolution but
    much is still unknown.
  • Progress comes from a wide variety of
    complementary particle physics, astrophysics and
    astronomy measurements.
  • One valuable component of these comes from
    ultra-low radioactivity experiments in deep
    underground locations looking for effects
    previously obscured by radioactive background.
  • Stay tuned for some fun future results, and
    improved perspective on our Universe!

54
The SNO Collaboration
J. C. Barton, S. D. Biller, R. A. Black, R.
Boardman, M. G. Bowler, J. Cameron, B. T.
Cleveland, G. Doucas, J. A. Dunmore, A. P.
Ferraris, H. Fergani, K.Frame, H. Heron, C.
Howard, N. A. Jelley, A. B. Knox, M. Lay, J. C.
Loach, W. Locke, J. Lyon, N. McCaulay, S.
Majerus, G. McGregor, M. Moorhead, M. Omori, S.
J. M. Peeters, C. J. Sims, N. W. Tanner, R.
Taplin, M. Thorman, P. T. Trent, H. Wan Chan
Tseung, N. West, J. R. Wilson, K. Zuber Oxford
University E. W. Beier, D. F. Cowen, J. Deng,
M. Dunford, E. D. Frank, W. Frati, W. J.
Heintzelman, P.T. Keener, C. C. M. Kyba, N.
McCauley,D. McDonald, M.Neubauer, F. M.
Newcomer, J. Seacrest, V. L. Rusu, R. Van Berg,
P. Wittich. University of Pennsylvania R.
Kouzes, M.M. Lowry, Princeton University S.N.
Ahmed, E. Bonvin, M. G. Boulay, M. Chen, E. T. H.
Clifford, Y. Dai, F. A. Duncan, H. C. Evans,
G.T. Ewan, R. J. Ford, G. Guillian, B. G. Fulsom,
K. Graham, W. B. Handler, A. L. Hallin, A. S.
Hamer, P. J. Harvey, R. Heaton, J. D. Hepburn,
C. Howard,C. Jillings, M. S. Kos, L. L. Kormos,
C. B. Krauss, C. Kraus, A. V. Krumins, H. W.
Lee, J. R. Leslie, R. MacLellan, H. B. Mak, J.
Maneira, A. B. McDonald, W. McLatchie, B. A.
Moffat, A. J. Noble, C. Ouellet, T. J.
Radcliffe, B.C. Robertson, P. Skensved, B. Sur.
Y. Takeuchi, M. Thomson,A.Wright Queens
University D.L. Wark, Rutherford Laboratory T.
Kutter, J. Goon, Louisiana State University J,
Maneira, N. Barros, LIP, Lisbon R.L. Helmer,
TRIUMF A.E. Anthony, J.C. Hall, M. Huang, J.R.
Klein University of Texas at Austin Q. R. Ahmad,
M. C. Browne, T.V. Bullard, T. H. Burritt, G. A.
Cox, P. J. Doe, C. A. Duba, S. R. Elliott, R.
Fardon, J. A. Formaggio, J.V. Germani, A. A.
Hamian, R. Hazama, K. M. Heeger, M. A. Howe, S.
McGee, R. Meijer Drees, K. K. S. Miknaitis, N. S.
Oblath, J. L. Orrell, K. Rielage, R. G. H.
Robertson, K. Schaffer, M. W. E. Smith, T. D.
Steiger, L. C. Stonehill, N. Tolich, B. L. Wall,
J. F. Wilkerson. University of Washington E.D.
Earle, G. Milton, B. Sur, AECL, Chalk River

deceased
  • S. Gil, J. Heise, B. Jamieson, R.J. Komar, T.
    Kutter,
  • S. M. Oser, C.W. Nally, H.S. Ng, R. Schubank,
  • Y. Tserkovnyak, T. Tsui, C.E. Waltham, J.
    Wendland
  • University of British Columbia
  • J. Boger, R. L Hahn, R. Lange J.K. Rowley, M. Yeh
  • Brookhaven National Laboratory
  • I. Blevis, A. Bellerive, X. Dai, F.
    Dalnoki-Veress, R. S. Dosanjh,
  • W. Davidson, J. Farine, D.R. Grant, C. K.
    Hargrove, L. Heelan,
  • R. J. Hemingway, I. Levine, K. McFarlane, H.
    Mes, C. Mifflin,
  • V.M. Novikov, M. O'Neill, E. Rollin, M. Shatkay,
    C. Shewchuk,
  • O. Simard, D. Sinclair, N. Starinsky, G. Tesic,
    D. Waller
  • Carleton University
  • T. Andersen, K. Cameron, M.C. Chon, P. Jagam, J.
    Karn,
  • H. Labranche, J. Law, I.T. Lawson,B. G. Nickel,
  • R. W. Ollerhead, J. J. Simpson, N. Tagg, J.X.
    Wang
  • University of Guelph
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