Measurement of the UHECR spectrum above 1E19 eV at the Pierre Auger Observatory using showers with zenith angles greater than 60 degrees.

THE PIERRE AUGER COLLABORATION (AUTOR 384 DE 427); M. J. TUEROS

Mérida, México

Conferencia; 30th International Cosmic Ray Conference; 2007

Instituto de Geofísica, UNAM

We report a measurement of the cosmic ray energy spectrum obtained using the inclined events detected with the Pierre Auger Observatory. Showers with zenith angles between 60◦ and 80◦ recorded in the period between 1 January 2004 and 28 February 2007 areanalysed. Showers are first reconstructed in arrival direction and then fitted to density mapsof the muon numbers obtained from 1E19 eV simulated proton showers for different arrivaldirections, in order to obtain the core position and an overall normalisation factor N19 which is used as an energy estimator. The parameter N19 is shown to be correlated with the shower energy measured with the fluorescence technique for a sub-sample of good quality hybrid showers. This correlation, measured with hybrid events, is then used to determine the energy of all the showers.