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 10 20 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 6x10 19 eV from traveling more than roughly 150 million light years

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

12. Auger Observatory

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

14. Fluorescence Detector

15. Shower Profile

16. 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

17. 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

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

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

20. APF Measurement

21. Geometrical Corrections

22. Phase Function Fit Mie: Rayleigh: Fit Function:

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

24. APF Fits

25. 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?

26. Effects on Energy Reconstruction

27. 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

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