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The main sources of background for the operation of the GLAST-Large Area Telescope are primary protons, albedo gammas from the earth and photons coming from interaction of positron and protons in the micro-meteoride-shield surrounding the LAT, which create photon pairs through annihilation and pi0 decay.
An extensive beam test campaign was performed in summer 2006 on the LAT Calibration Unit (CU), a detector built with flight spare parts of the LAT; the goal of the program was to support the LAT Instrument Calibration by providing direct measurements of the physical processes taking place in the CU detector when exposed to different beams, by comparing the obtained measurements with Monte Carlo predictions and by eventually validating the full LAT MC code used to provide instrument calibrations and background rejection strategies.
The study of the background signal produced in the CU by sources of the LAT background was performed with photon beams shooted from the side of the CU, and protons and positrons beams reaching the CU after crossing an MMS target.
Results from analysis of these data are presented in this talk.