The Search for Proton Decay at Super-Kamiokande

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The Search for Proton Decay at Super-Kamiokande

• ASTR-007
• Theodore Liu

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Proton Decay overview

• Protons not infinitely stable, as once thought
• Required for grand unification theories
• Binds the electromagnetic, weak, and strong
  forces into one single force
• Existed about 10-40 seconds after Big Bang, with
  a temperature of around 1027 K

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Proton Decay specifics

• If grand unification occurs, quarks would be able
  to transform into leptons through the exchange of
  a supermassive particle dubbed the X boson.
• This process requires that protons decay to form
  the quarks, something generally not allowed by
  the Standard Model.

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Search for Proton Decay

• Proton decay would have to occur over extremely
  long time scales, or else the matter of the
  universe would not hold together.
• Experiments to detect proton decay can only
  establish a lower limit for a protons half-life.

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Search Methods specifics

• A proton typically decays into a positron and a
  neutral pion.
• Positron annihilates with an electron.
• Pion almost immediately decays into two photons
  in the gamma range.
• If the reaction is in water, the radiation
  released is known as Cerenkov radiation and can
  be detected.

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Cerenkov Radiation

• When a particle moving faster than
• the speed of light in water enters
• water, it slows down to adjust to
• the local speed of light of the
• new medium. This produces a
• cone of light analogous to how a
• supersonic jet will produce a sonic
• boom.

Cerenkov radiation giving off its characteristic
blue glow in a UMR reactor core
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Super-Kamiokande

• Massive neutrino observatory situated insided an
  active zinc mine in Mount Ikenoyama, Japan
• Contains 50,000 tons of ultrapure water, lined
  with more than 11,000 photomultiplier tubes to
  detect Cerenkov radiation

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Super-Kamiokande findings

• No detected proton decay yet since observations
  began in 1996
• Does not mean that proton decay is not possible,
  simply that the lower bound is in the range of
  1035 years

Interior of the Super-K detector
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Works Cited

• http//hyperphysics.phy-astr.gsu.edu/HBASE/particl
  es/neutrino2.htmlc1
• http//hep.bu.edu/superk/pdk.html
• http//en.wikipedia.org/wiki/Proton_decay
• Halcomb Hawley