On the way to the determination of the cosmic ray mass composition by the Pierre Auger fluorescence detector: The 'minimum momentum method'

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.