1. 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 2

2. Volcano Radiography Internal structure of volcanoes not very well known Use cosmic rays to do radiographical scanning 3

3. 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) 4

4. Volcano Radiography Mt. Iwatodake, Japan (Tanaka et al.) 5

5. National Security Safety of cargo an issue Nuclear material could be smuggled Many scanning methods (X-ray, neutrons, etc.) But generally expensive, and may introduce radiation Alternative: cosmic rays 6

6. Neutrinos 7 (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)

7. Solar Neutrino Problem 8 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

8. Neutrino Oscillation 9 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 experiments expected (and saw) only electron neutrinos Must have mass to oscillate

9. 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…? 10

10. Super-Kamiokande 11 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

11. Super-K Neutrino Event 12

12. Super-K Maintenance 13

13. Large Arrays - ANTARES 2.5 km under Mediterrenean sea (near Toulon) 1 km³ array at 2.5 km depth 900 detectors (photomultipliers) 14

14. Large Arrays - IceCube Amundsen-Scott South Pole Station 1.5 - 2.5 km under surface 86 detector strings 5160 sensors 15

15. Any Questions? 16

16. Backup Slides 17