Aerosol attenuation measurements for cosmic rays experiments: the Pierre Auger Observatory experience and the ARCADE project

The characterization of the optical properties of the atmosphere in the near UV, in particular the tropospheric aerosol attenuation, is a topic strongly needed by the cosmic rays physics community. In a cosmic rays experiment, for energies greater than 10^18 eV, the identification of the properties of a primary particle is obtained through the study of the shower of particles generated by their interaction in the atmosphere. One of the techniques commonly used to achieve this goal is based on the detection of the UV fluorescence light that the nitrogen molecules of the atmosphere emit after the interaction with the particles of the shower. The most significant and variable phenomenon that affects the measurements of the fluorescence light is the scattering of light due to aerosols, infact a correct estimation of the aerosol attenuation can lead to a correction of the energy of the shower that can range from a few percent to more than 40%. For this reason cosmic rays experiments need a network of instruments for a continuous monitoring of the aerosol attenuation. Within the activities described above, during my PhD I have been working within the Pierre Auger Collaboration and in the ARCADE project. My activity in the Auger Collaboration has been focused on the analysis of data obtained using the two laser facilities of the observatory (CLF and XLF). The analysis of the light emitted by the lasers and collected by the Fluorescence Detector after side-scattering within the atmosphere is used to measure the atmospheric aerosol attenuation. In this work I present results of the analysis of the XLF data that I performed for the first time, the work done for the release a new version of the whole Auger Aerosol Database that is used for air shower analysis, and the modifictions I performed on the data analyss method in order to obtain more precise results. The ARCADE project is a three year project started in 2012 and funded by the MIUR that was conceived to solve the open problems affecting the measurements of aerosol attenuation obtained with the typical techniques used in cosmic rays experiments. The experiment that takes place in Lamar (Colorado) makes use of a steerable lidar that was fully designed within the project, and an UV detector. I took part to all the phases of a new experiment, from the design, to the realization and finally to the development of the data analysis methods. All the the details of the project are described, and all my first hand contributes to its realization are highlighted. The description of the analysis methods that I developed for the data analysis of both devices is described, togheter with some preliminary results.