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First Analysis of the Auger APF Light Source

First Analysis of the Auger APF Light Source. Eli Visbal (Carnegie Mellon University) Advisor: Stefan Westerhoff. Overview. Cosmic Rays and Auger Atmospheric Calibration Overview APF Light Sources Determination of Aerosol Phase Function Fluorescence Detector Event Reconstruction

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First Analysis of the Auger APF Light Source

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  1. First Analysis of the Auger APF Light Source Eli Visbal (Carnegie Mellon University) Advisor: Stefan Westerhoff

  2. Overview • Cosmic Rays and Auger • Atmospheric Calibration Overview • APF Light Sources • Determination of Aerosol Phase Function • Fluorescence Detector Event Reconstruction • Problems and Future Work • Summary and Conclusions

  3. Cosmic Rays • Cosmic Rays are very energetic particles • These particles can have energies over 1020 eV • When these particles enter the atmosphere they produce a shower of lower energy secondary particles • The origin of those with highest energies remains a mystery • This is in part due to magnetic deflection • GZK cutoff prevents particles above 6x1019 eV from traveling more than roughly 150 million light years

  4. Pierre Auger Observatory • Hybrid detector • Located in Malargue, Argentina • 4 Fluorescence Detector and 1600 Surface Detector Stations

  5. Auger Observatory

  6. Fluorescence Detector • Cosmic Rays are studied by observing nitrogen fluorescence light caused by relativistic electrons created in a shower

  7. Fluorescence Detector

  8. Shower Profile

  9. Atmospheric Calibration • Cherenkov beam builds up along shower axis • Atmospheric transmission • Multiple scattering • Aerosol (Mie) and Molecular (Rayleigh) scattering • Aerosol phase function (normalized differential scattering cross section) must be known to account for multiple-scattering and Cherenkov subtraction

  10. APF Light Sources • APF light sources shoot a near-horizontal pulse across the field of view of a FD • One FD at Coihueco and one at FD Los Morados • Wavelengths used: ~330nm, ~360nm and ~390nm

  11. APF Light Sources Coihueco FD Alpha ~ 26 degrees Beta ~ 38 degrees Gamma ~ 20 degrees

  12. APF Shot APF Shot as seen by the Coihueco fluorescence detector

  13. APF Measurement

  14. Geometrical Corrections

  15. Phase Function Fit Mie: Rayleigh: Fit Function:

  16. APF shot Angle Determination Rayleigh Dominated Data • A Rayleigh dominated night was found • According to theory scattering should be symmetric about 90 degrees Scattering angle [radians]

  17. APF Fits

  18. FD Reconstruction • Signal that reaches the telescope must be processed with reconstruction software to measure total energy • Simulated aerosol phase function used now • How big of correction when applying measured function?

  19. Effects on Energy Reconstruction

  20. Current Problems • Unstable fit • Geometry of APF needs to be measured • High angle and low angles not fit • Only one wavelength currently used • Quality of data • Too Many Parameters in Fit

  21. Conclusions • Aerosol phase function measured successfully • Energy correction less than 1% • Some additional work required

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