Transcript Neutrino Mass By Ben Heimbigner Overview of the Presentation • History of the Neutrino • Neutrino Oscillations and the relation to mass. • Observations of.

Neutrino Mass
By Ben Heimbigner
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Overview of the Presentation
• History of the Neutrino
• Neutrino Oscillations and the relation to
mass.
• Observations of Neutrinos
– Super Kamiokande (Super K)
– Sudbury Neutrino Observatory (SNO)
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What is a Neutrino?
• Fundamental particle belonging to the
Lepton family
• Predicted 1930 by W. Pauli and first
observed in 1956.
• No Strong or Electromagnetic reaction
along with a very small mass make them
hard to detect.
• Three types also called flavors: Electron
Muon and Tau.
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Solar Neutrino Problem
• First Noticed in the 1960’s by Ray Davis
– Used a large tank of Perchloroethylene and observed
the conversion of chlorine to radioactive argon
– Major Disagreement (30% of predicted value)
between the predicted neutrino numbers that should
be reaching earth and the measured values.
• At the time it was uncertain what was causing
this major disagreement between theory and
experiment.
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Current Detection of Neutrinos
• Cherenkov Radiation
– Interaction between sub atomic
particles in water and Neutrinos.
• Caused when a particle goes faster
than the speed of light within a
medium. The electron moves faster
than its electric field can propagate
similar to a sonic boom.
– Common example is when a
neutrino hits an electron in water.
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Other Methods of Detecting
Neutrinos
• Radiochemical
– Rely on the neutrino interacting with a particle
and changing it into something else such as
Chlorine into Argon.
• Scintillation
– Particle is absorbed by the substance and
then substance fluoresces at specific known
wavelengths.
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Why Does Neutrino Oscillation
mean Neutrino Mass.
• The two properties are intrinsically related
– If Neutrinos are oscillating it means they must
have mass.
• This flavor oscillation is caused because
the neutrinos can’t be in an eigenstate for
energy and mass at the same time.
– This causes the Neutrinos to have flavor
oscillations.
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Neutrino Oscillation Math
We start out with two equations describing the Neutrinos
states. Va describes the flavor, either electron, muon or
tau. Vi describes the neutrino mass, 1, 2 or 3.
Sense Vi are mass eigenstates we can describe their
propagation by standard plane wave solutions:
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Neutrino Oscillation Cont
If we use the ultra relativistic case we can describe Ei from the
previous equation as:
Inserting that into our previous equation we have:
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Derivation Finished
From the Previous equation we can find out the probability
that a neutrino of one flavor will oscillate into a different
flavor
What’s most important for us is that this term is
dependent on the squared difference of masses
between the two flavors. This means for there to be
oscillations there needs to be neutrino mass.
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How do we Know they are
oscillating?
• 1998 Super-Kamiokande
– Detection of Similar numbers of Muon and
Electron Neutrinos instead of 2:1 ratio
predicted.
• Indicated that some of the Muon neutrinos were
oscillating into Tau neutrinos.
• Sudbury Neutrino Observatory (SNO)
– Sensitive to electron and total neutrino flux.
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Why is Neutrino Mass a big deal?
• In the Standard Model Neutrino’s were
considered to be Massless.
– However they have been found to have a
mass this presents us with physics that are
outside the realm of the Standard Model.
• Previous to recent experiments all other
observations had supported that neutrino’s
had zero mass.
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Details on Super K
• Massive 50,000 ton cylinder of pure water
• Located 1000m underground within a mine
so as to isolate the environment from
outside interference such as cosmic rays.
• 11,200 Photomultiplier tubes contained
within for detection of light from Cherenkov
radiation.
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Super Kamiokande Experiment
• Super-K is a water imaging Cherenekov
detector.
– Neutrino comes in and hits an electron
creating Cherenekov radiation
– Photomultiplier tubes surrounding the water
tank then pick up the light emitted from
Cherenekov radiation.
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Outside View of Super K
•
Picture From: http://www-sk.icrr.u-tokyo.ac.jp/sk/index-e.html
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Super Kamiokande
Photo from: http://www-sk.icrr.u-tokyo.ac.jp/sk/index-e.html
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Super-K Findings
• They found that there was strong evidence
point towards a muon to tau neutrino
oscillation from their atmospheric results
instead of other possibilities such as sterile
neutrinos or no oscillations.
• The solar model also found evidence
although less direct of neutrino oscillations
from the night day differences.
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SNO
• 9600 PMT’s
• Located 2070 meters
below ground in
Creighton mine.
• 1000 tons of heavy
water.
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SNO Detector
SNO Detector viewed
from the bottom, it is
12 meters in
diameter.
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SNO Experiment
• Able to detect three different reactions.
Elastic Scattering
(ES)
Charged Current
(CC)
Neutral Current (NC)
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SNO Results
• By measuring all three reactions they were
able to find that there was an excess of
Neutral current flux over the elastic
scattering and charged current. This
means that there is an excess of total
neutrinos (measured by NC) compared to
electron neutrinos (measured by charged
current).
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Sources
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Super K Web Site: http://www-sk.icrr.u-tokyo.ac.jp/sk/index-e.html
SNO Website: http://www.sno.phy.queensu.ca/
http://www.ps.uci.edu/~superk/oscillation.html
Theory Of Neutrino Oscillations
(http://www.citebase.org/fulltext?format=application%2Fpdf&identifier=oai%
3AarXiv.org%3Ahep-ph%2F0409230)
http://www-sk.icrr.u-tokyo.ac.jp/sk/pub/koshio-proc.pdf
http://www-sk.icrr.u-tokyo.ac.jp/sk/pub/svoboda-tau2000.pdf
Various Wikipedia articles.
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