Pyramid Scanning (~1970)

• Luis Alvarez (1970): Are there undiscovered chambers in the Chephren pyramid?

• Investigate with cosmic rays

• Detector installed in chamber at the bottom (B)

• Results compared to what would have been expected from a hidden chamber

• Ultimately, hidden chamber was ruled out

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Volcano Radiography

• Internal structure of volcanoes not very well known

• Use cosmic rays to do radiographical scanning

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Volcano Radiography

• Measure cosmic ray flux through volcano

• Obtain 2D density map

• Lots of data needed

• Then again, geologists have time…

Puy-de-dôme in Clermont-Ferrand, France(ToMuVol project)

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Volcano Radiography

Mt. Iwatodake, Japan (Tanaka et al.)

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National Security

• Safety of cargo an issue

• Nuclear material couldbe smuggled

• Many scanning methods(X-ray, neutrons, etc.)

• But generally expensive,and may introduce radiation

• Alternative: cosmic rays

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Neutrinos

6(has been confirmed)

• Necessary to explain beta decay:

• Postulated 1930 by Wolfgang Pauli

• (Wasn’t too happy about it)

• Assumed to be massless, neutral cousin of the electron

• Almost no interaction with matter

• Still, discovered experimentally (1956 in a nuclear reactor, Cowan-Reines experiment)

Solar Neutrino Problem

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• The sun is essentially a huge fusion reactor

• Produces large amounts of neutrinos

• Neutrinos can be measured as they arrive on earth

• Wrong amount of neutrinos found!

• Fewer neutrinos arrive than expected from solar models

Neutrino Oscillation

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• Maybe solar models wrong?

• Turns out, nope.

• Problem resolved when neutrino oscillation was discovered

• Neutrinos switch back and forth between generations as they fly

• Initial experimentsexpected (and saw) onlyelectron neutrinos

• Must have mass to oscillate

Why Study Neutrinos?

• Good probes for astrophysics:

• Investigate the core of the sun

• Produced in supernovae (in fact, ~99% of a supernova’s energy is radiated in neutrinos)

• Travel very far (and don’t care about the GZK limit)

• Interesting in fundamental particle physics:

• Exact masses? ‘Sterile’ neutrinos? More flavours…?

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Super-Kamiokande

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• Neutrinos interact very little

• Need huge detection volumes

• Super-Kamiokande detector in Japan

• Giant tank of water with photodetectors

• Saw the first measurement of neutrino oscillation

Super-K Neutrino Event

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Super-K Maintenance

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Large Arrays - ANTARES

2.5 km under Mediterrenean sea (near Toulon) 1 km³ array

at 2.5 km depth 900 detectors

(photomultipliers)

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Large Arrays - IceCube Amundsen-Scott South Pole Station 1.5 - 2.5 km under surface 86 detector strings 5160 sensors

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Any Questions?

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Backup Slides

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