We propose a possible approach for the determination of very high energy cosmic ray primary mass A based on the information provided by the reconstruction of shower longitudinal development in the Earth atmosphere. We refer to an apparatus such as the Pierre Auger Observatory, which is a unique "hybrid" UHECR detector. The surface detector (SD) and air fluorescence detector (FD) of the observatory are designed for observation of cosmic ray showers in coincidence, with a 10% duty cycle, with resulting data expected to be superior in quality especially for the primary energy E-0 which is determined with a 5% accuracy. We present results obtained using an approach for the determination of A in the individual event based on only FD information (MMM - 'Minimum Momentum Method'). This approach shows that, if the entire information contained in the longitudinal profile is exploited, reliable results may be obtained.
On the way to the determination of the cosmic ray mass composition by the Pierre Auger fluorescence detector: The 'minimum momentum method' / Aramo, C.; Ambrosio, M.; Donalek, C.; D'Urso, D.; Erlykin, A. D.; Guarino, F.; Insolia, A.; Longo, G.; Tagliaferri, R.. - (2003), pp. 13-19. ((Intervento presentato al convegno Thinking, Observing and Mining the Universe tenutosi a Sorrento, Italy nel 22-27 Sep 2003.