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Cosmic rays above 10 17 eV; the highest energy particles

A Cross Check of Atmospheric Attenuation for the High Resolution Fly’s Eye Astroparticle Experiment Chris Cannon Advisor: Lawrence Wiencke University of Utah. Cosmic rays above 10 17 eV; the highest energy particles Atmospheric attenuation plays a significant role in detector calibration.

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Cosmic rays above 10 17 eV; the highest energy particles

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  1. A Cross Check of Atmospheric Attenuation for the High Resolution Fly’s Eye Astroparticle Experiment Chris Cannon Advisor: Lawrence Wiencke University of Utah • Cosmic rays above 1017 eV; the highest energy particles • Atmospheric attenuation plays a significant role in detector calibration. • Cross check atmospheric calibration • Results • Conclusion

  2. Cosmic Ray Energy Spectrum Flux E^3 Man-made accelerators At energies above 1020 eV the flux is extremely low!!! Namely 1 particle/km2-steradian/century

  3. Using the Atmosphere as a Detector

  4. Introducing High Resolution Fly’s Eye (HiRes)

  5. HiRes Camera Mirror PMT Cluster

  6. Display of a Sample Air Shower

  7. The Atmosphere – Two Components Vertical Aerosol Optical Depth (VAOD) is the optical thickness of the aerosol component of the atmosphere. Transmission(aerosol) = e-VAOD Aerosols Molecular

  8. Measuring VAOD with Atmospheric Lasers HiRes-2 laser system HiRes-1 detector 12.6 km Average VAOD: 0.04 +- .02

  9. Measuring VAOD with Cosmic Rays detector 2 Reality detector 1 Erroneous Simulation - Overcorretion apparent shower 2 apparent shower 1 apparent shower 2 Erroneous Simulation - Undercorrection apparent shower 1

  10. Data Selection • Start with 2079 cosmic rays seen by both detectors. • Require that: • The two detectors see a common portion of the shower. • Each detector must collect at least 1000 photons from the common track segment, which must be at least 5 degrees long. • The probability that the event is noise based on a random walk model is less than 5%. • The event is downward going. • The opening angle between shower-detector planes is greater than 25 degrees. • The scattering angle is at least 25 degrees. • 1218 cosmic ray events remain. Purpose of Cuts: Remove noisy, dim events. Ensure good geometry. Remove Cherenkov dominated events.

  11. Use the segment of the shower viewed by both detectors. Profile integration Luminosity (photons/m) Luminosity (photons/m) Distance from Gound (m) Distance from Gound (m)

  12. Plotting Data Greater distance brighter shower. The atmosphere is over-corrected. Difference in shower brightness - 0 + Greater distance dimmer shower. The atmosphere is under-corrected. - 0 + Difference in distance between detectors and shower

  13. Results Simulated Atmosphere Canonical Model Measured Average No Aerosols Comment Over-correction Under-correction

  14. Conclusion: VAOD Measurement Using cosmic rays .043 +- .001 (stat) Using lasers .04 +- .02

  15. Effect of Atmospheric Calibration 1999 2003 With Model Atmosphere With Measured Atmosphere

  16. Greisen-Zatsepin-Kuzmin (GZK) Cutoff Charged particles with E > 5 x 1019 eV will travel at most 100 Mpc before their energy drops below the cutoff.

  17. HiRes Atmospheric Works in Progress • Improved atmospheric monitoring: • Hourly aerosol corrections instead of average. • Cloud monitoring.

  18. Sources of Cosmic Rays • The Sun • Solar Wind • Low Energy < 10 GeV • Supernovae Capable of accelerating particles to 1015eV • AGNs / GRBs … Possible sources for UHECRs

  19. Requirements on acceleration size and field strength

  20. Geometry with One Eye shower Equal Angle Bins Rp ψ detector Use Timing…. Depth Perception is Limited Need to measure a change in angular velocity Works best with Longer track Larger Rp Smaller ψ

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