First Analysis of the Auger APF Light Source

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First Analysis of the Auger APF Light Source

• Eli Visbal (Carnegie Mellon University)
• Advisor Stefan Westerhoff

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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

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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

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Pierre Auger Observatory

• Hybrid detector
• Located in Malargue, Argentina
• 4 Fluorescence Detector and 1600 Surface Detector
  Stations

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Auger Observatory
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Fluorescence Detector

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

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Fluorescence Detector
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Shower Profile
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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

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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

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APF Light Sources
Coihueco FD Alpha 26 degrees Beta 38
degrees Gamma 20 degrees
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APF Shot
APF Shot as seen by the Coihueco fluorescence
detector
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APF Measurement
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Geometrical Corrections
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Phase Function Fit
Mie
Rayleigh
Fit Function
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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
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APF Fits
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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?

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Effects on Energy Reconstruction
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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

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Conclusions

• Aerosol phase function measured successfully
• Energy correction less than 1
• Some additional work required