Small Matters with Big Consequences

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Small Matters with Big Consequences
Sam Zeller Columbia University NeutrinoFest April
18, 2005

• n physics marked by unexpected results
• that have had deep significance
• surprising results that ns have uncovered
• incredible experiments
• - with emphasis on potential for further
  discovery
• at future planned experiments

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Surprise 1 Neutrinos Exist?!
1930 Wolfgang Pauli postulates new,
elusive subatomic particle (n) which
carries away missing energy in b decay
n
Pauli

• saves energy conservation
• but introduced a brand new particle ? n
• drastic remedy very bold thing to do
• oh by the way, n difficult to detect

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Surprise 2 Can Detect Neutrinos!
25 years later, Reines/Cowan finally observe
antineutrinos emitted by a nuclear reactor
----------------------------- W E S T E R N U N
I O N -----------------------------
June 14, 1956 Dear Professor Pauli,
We are happy to inform you that we have
definitely detected neutrinos. . .
Fred Reines Clyde Cowan
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Surprise 3 Three Neutrinos
e
m
t
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Surprise 4 New Type of Interaction!
this is how we detected neutrinos in the first
place
weak processes always transform nm into m ??
standard model being developed claims
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Surprise! NuTeV n Results
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Surprise 5 Neutrinos Oscillate!
astonishing sequence of experiments have
revealed that neutrinos oscillate observation
shook the n community
combination has forced us to modify our thinking
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Surprise! Two Many Oscillation Signals
mass difference

• 3 neutrinos ? 2 independent
• mass differences, we see 3?!
• LSND seeing oscillations?
• one possible interpretation
• at least one extra n! (sterile n)

mixing
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Are there More Neutrinos?(did LSND really
observe oscillations?)
MiniBooNE experiment (U.S.) will address this
question
nm ? ne ??
much-anticipated answer expected later this year
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Surprise! Neutrino Mixing
(solar neutrino data 8 years ago)
another peculiar feature revealed by n
oscillation data is the size of the n mixing
quark mixing small neutrino mixing small ??
(M. Cirelli, A. Strumia)
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Surprise! Neutrino Mixing is Different
lepton mixing turns out to be quite distinct
from quark mixing
(M. Cirelli, A. Strumia)
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Surprise! Neutrino Mixing is Different
quark mixing small neutrino mixing LARGE (at
least for 2 of the mixing angles)
(M. Cirelli, A. Strumia)
in addition to this unexpectedly large mixing
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Surprise! mn is very small
we dont know why masses are distributed this way
mass (eV)
(A. De Gouvea)

• heaviest n is at least a million times lighter
  than
• lightest charged particle (electron) why so
  much lighter?
• nothing in between? n-electron gap is deserted?!

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mn How Small Is Small?

• oscillation experiments are only sensitive to
• differences between n masses (Dm2)
• rely on other types of exps to tell us mn

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Poised for More Surprises?

• now that have established that ns have mass and
  mix,
• this raises more questions

answers can only be determined by experiments
do neutrinos behave any differently
from antineutrinos ?
what is mn?
are neutrinos their own antiparticles?
what is the pattern of mixing among the ns?
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Next Generation n Oscillation Exps(will provide
us with best window)
proton driver (more intense n
sources) JPARC/T2K (Japan)
long baseline n experiments (NOvA, U.S.)
reactor experiments (Josh Kleins talk)
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Long Baseline n Experiments
increase physics capability ? long distances,
large detectors (strongly improve our knowledge)

• NOvA (U.S.)
• even longer baseline
• 24,000 tons liquid scintillator

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Long Baseline n Experiments
long distances, large detectors ? important
questions
ok, so how large is that really?
NOnA
15.7 m
132 m
15.7 m
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Even Longer Baselines

• U.S. can play a unique role

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Precision Neutrino Scattering Exps

• broad exciting program of n physics built upon
  
• precisely knowing how ns interact with matter
• new fine-grained detectors being planned to
  ensure
• that future oscillation experiments have what
  they need

MINERvA (U.S.)
FINeSSE (U.S.)
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Need All Types of Experiments
consistent picture has been the result of careful
testing repetition of important experiments
v
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CHARM II

• neutrinos have surprised us with their
• unexpected behavior for the past 75 years
• it is certain that ns have not exhausted their
• ability to surprise the physics community
• shape our understanding of Nature
• new n discoveries on horizon might again
• force a profound revision in our thinking
• with current future planned experiments
• - were in store for an exciting ride!