The cosmic ray flux observed at zenith angles larger than 60 degrees with the Pierre Auger Observatory

THE PIERRE AUGER COLLABORATION (AUTOR 434 DE 474); M. TUEROS

Lodz, Polonia

Conferencia; 31st International Cosmic Ray Conference; 2009

The cosmic ray energy spectrum is obtained using inclined events detected with the surface detectors of the Pierre Auger Observatory. Airshowers with zenith angles between 60 and 80 degrees add about 30% to the exposure. Events are identified from background based on compatibility between the arrival time and the detector location enabling the elimination of random signals. The arrival directionis computed using the time information. The core position and a shower size parameter are obtained for each event by fitting measured signals to those obtained from predictions of two-dimensional distributions of the patterns of the muon densities at ground level. The shower size parameter, a zenith angle independent energy estimator, is calibrated using the shower energy measured by the fluorescence technique in a sub-sample of high-quality hybrid events. The measured flux is in agreement with that measured using showers of zenith less than 60degrees.