Measurement of the UHECR spectrum above 10 EeV at the Pierre Auger Observatory using showers with zenith angles greater than 60 degrees

Understand

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 degrees recorded in the period between 1 January 2004 and 28 February 2007 are analysed.
• Showers are first reconstructed in arrival direction and then fitted to density maps of the muon numbers obtained from 10 EeV simulated proton showers for different arrival directions, 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.