Speaker: Gordon Thompson, Rutgers University.

Title: Observation of the GZK Cutoff by the HiRes Experiment

Summary:
The High Resolution Fly's Eye (HiRes) experiment has observed the GZK
cutoff.  HiRes' measurement of the flux of cosmic rays shows a sharp
suppression at an energy of 6 x 10^19 eV, exactly the expected cutoff  
energy.
  We observe the ``ankle'' of the cosmic ray spectrum as well, at an  
energy of 4 x 10^18 eV.  I will describe the experiment, data collection, and  
analysis, and estimate the systematic uncertainties.  I will present the  
results and the calculation of a five standard deviation observation of the GZK cutoff.