1. Cosmic Ray Workshop May 15, 2010 1 May 15, 2010 Rutgers Cosmic Ray Workshop

2. Cosmic Ray Workshop May 15, 2010 2 Cosmic Rays Earth is continually bombarded by particles from outer space What are they? Where do they come from? How are they created? How do we detect them?

3. Cosmic Ray Workshop May 15, 2010 3 Discovery of Cosmic Rays Cosmic rays discovered in 1912 by Victor Hess measured radiation levels aboard a balloon up to 17,500 feet (without oxygen) found increasing radiation levels at higher altitudes

4. Cosmic Ray Workshop May 15, 2010 4 Primary Particle Flux flux falls ~30 orders of magnitude, spanning 12 orders of magnitude in energy Power Law Intensity ~ E – 2.7 look for features seems monotonous but

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6. 6 At the Surface of the Earth ~ 2 particles per second through outstretched hand Rule of Thumb: irreducible source of natural radioactivity 28 mrem/year at sea level twice as much if you live in Denver mostly muons (and neutrinos) primary cosmic rays interact in the atmosphere

7. Cosmic Ray Workshop May 15, 2010 7 What are the cosmic ray particles? Must be stable in order to get here protons electrons neutrinos photons nuclei (He  Fe) Not neutrons neutron lifetime ~ 15 minutes what about antiparticles anti protons positrons anti nuclei Not seen we live in matter universe

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10. 10 Composition 80% protons 15% He 0.1% photons rest mostly C and Fe some electrons below 10 GeV generally depends on energy

11. Cosmic Ray Workshop May 15, 2010 11 Where do the Cosmic Rays Come From? Basically we’re not sure!

12. Cosmic Ray Workshop May 15, 2010 12 Primary Cosmic Ray Flux

13. Cosmic Ray Workshop May 15, 2010 13 Cosmic Ray Air Shower

14. Cosmic Ray Workshop May 15, 2010 14 Particles at Surface