Multiple scattering measurement with laser events
09 Sep 2011
1LIP, Av. Elias Garcia, 14-1, 1000–149 Lisbon, Portugal
2Departamento de Física, IST, Av. Rovisco Pais, 1049-001 Lisbon, Portugal
3Observatorio Pierre Auger, Av. San Martin Norte 304, (5613) Malargüe, Mendoza, Argentina (Full author list: http://www.auger.org/archive/authors_2010_08.html)
Abstract. The Pierre Auger Observatory Fluorescence Detector (FD) performs a calorimetric measurement of the primary energy of cosmic ray showers. The level of accuracy of this technique is determined by the uncertainty in several parameters, among them the fraction of shower light (both from fluorescence and Cherenkov light) that reaches the detector after being multiply scattered (MS) in the atmosphere. This component depends on atmospheric conditions, namely on Rayleigh and Mie scattering processes. Using laser events it is possible to study these processes and deconvolute them from the shower's electromagnetic lateral distribution.
We propose a new method to measure the Rayleigh and Mie MS components seen in laser events, and correlate them with atmospheric conditions. In order to study in detail the effect of such conditions in the scattering of photons, a Geant4 dedicated laser simulation was developed. % In this framework photons are individually followed through the atmosphere allowing for any number of scatterings, from both processes This combination of a MS dedicated data analysis with a realistic laser simulation enables to explore MS characteristics, in particular the evolution with time, altitude and distance from the FD.