IAFE   05512
INSTITUTO DE ASTRONOMIA Y FISICA DEL ESPACIO
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
On the statistics of the mean value determination of the depth of maximum for extensive air showers
Autor/es:
A. D. SUPANITSKY; G. A. MEDINA-TANCO
Reunión:
Conferencia; 33RD INTERNATIONAL COSMIC RAY CONFERENCE, RIO DE JANEIRO 2013 THE ASTROPARTICLE PHYSICS CONFERENCE; 2013
Resumen:
The nature of the primary cosmic ray at the highest energies is still a matter of debate. The latest results obtained by the Pierre Auger Observatory, concerning the measurement of the mean value and the fluctuations of the atmospheric depth at which the showers reach the maximum development, Xmax, are inconsistent with the ones obtained by the HiRes Collaboration. From comparison with air shower simulations it can be seen that, while the Auger data may be interpreted as a gradual transition to heavy nuclei for energies larger than ~2-3 x 10^18 eV, the HiRes data are consistent with a composition dominated by protons. Recently, the Telescope Array experiment reported the measurement of the mean value of Xmax as a function of primary energy. The Telescope Array data is consistent with a composition dominated by protons, which is in agreement with the Hires results. It has been suggested that a possible explanation of the deviation of the mean value of Xmax from the proton expectation observed by Auger could be explained by a statistical bias originated as a consequence of the asymmetry of the Xmax distribution combined with the decrease of the number of events as a function of primary energy. We show in this work that considering a better description of the Xmax distribution the suggested bias becomes negligible and then we conclude that the deviation of the Auger data from the proton expectation cannot be explained by this statistical effect.