Air fluorescence studies at the Pierre Auger Observatory

by Sarah Clay

Institution: University of Adelaide
Year: 2007
Keywords: Cosmic rays; Atmospheric physics; Cherenkov radiation
Record ID: 1032756
Full text PDF: http://hdl.handle.net/2440/37993


Cosmic rays measured by the fluorescence detectors of the Pierre Auger Observatory contain two large sources of error; the degree of scatter created by the atmosphere and the amount of Cherenkov contamination that has been recorded by a detector. When an event is viewed in stereo, these two sources of error can be accounted for directly by using the light profiles calculated by the two detectors. In this thesis accounting for the atmospheric scatter was explored by the use of a program called AerosolMin described in Chapter 5. This program could reconstruct the scattering parameters of the atmosphere by comparing the two profiles of the light produced by an air shower, as calculated by two detectors, as they should be identical in size. When using AerosolMin it was found that only the highest energy events ( > 10 [superscipt 20] eV ) could use this technique and that for the event that occurred at the GPS second of 799137161 a layer of fog was present that could not be accounted for with the simplistic atmospheric profile currently used by the reconstruction software. In Chapter 6 the Cherenkov profiles that had been miscalculated by a detector were replaced to increase the reconstruction statistics. The program that performed this replacement, FdCherenkovReplacer was most successful on events that had recorded a large amount of direct Cherenkov light. The event that occurred at the GPS second of 772256331 is explored in Chapter 7. The Coihueco detector that recorded this event was contaminated by direct Cherenkov light, but when replaced by FdCherenovReplacer it was found to have miscalculated the geometry of the event by 0.4 °.