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 Problems and Future Work Summary and Conclusions

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

Pierre Auger Observatory

Hybrid detector Located in Malargue,

Argentina 4 Fluorescence

Detector and 1600 Surface Detector Stations

Auger Observatory

Fluorescence Detector

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

Fluorescence Detector

Shower Profile

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

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

APF Light Sources

Coihueco FD

Alpha ~ 26 degrees

Beta ~ 38 degrees

Gamma ~ 20 degrees

APF Shot

APF Shot as seen by the Coihueco fluorescence detector

APF Measurement

Geometrical Corrections

Phase Function Fit

Mie:

Rayleigh:

Fit Function:

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

APF Fits

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?

Effects on Energy Reconstruction

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

Conclusions

Aerosol phase function measured successfully

Energy correction less than 1% Some additional work required