Speaker
Zhen Cao
(IHEP, Beijing, China)
Description
The UHECR energy spectrum above 10^18.2 eV is measured by the HiRes stereo experiment using data taken from December 1999 to November 2006. A fully efficient aperture with minimal weather dependence is defined from 100 km^2 sr (at 10^18.2 eV) to 10000km^2 sr (at 10^20.5 eV). A clear "ankle" structure is observed at 10^18.7 eV with a confidence level of 99.7%. A GZK feature above 10^19.7 eV is observed as a 4.3 sigma deviation from an extension of a two component power law spectrum.
