Statistical and systematic uncertainties in the event reconstruction and   S(1000) determination by the Pierre Auger surface detector
  We discuss the statistical and systematic uncertainties in the event reconstruction (core location, and determination of S(1000), i.e., the signal at a distance of 1000 m from the shower core) by the Pierre Auger surface detector for showers with zenith angle less than 60 degrees. The method is based on a maximum likelihood method where the reference lateral distribution function is obtained through the experimental data. We also discuss S(1000) as primary energy estimator. 
Pierre Auger Collaboration