The High Resolution Fly's Eye (HiRes) Experiment
measures the energy spectrum, chemical composition and arrival
directions of cosmic rays above 1018 eV. By mapping the Universe at
these highest particle energies, HiRes will help to bring us closer
to an understanding of where these particles come from, how they are
accelerated, and how they travel astronomical distances.
Located in the dry atmosphere of the Utah desert, the HiRes
detector consists of a large number of focusing mirrors that image
fluorescence light from distant air shower cascades onto arrays of
photomultiplier tubes. HiRes comprises two detector sites that provide
stereoscopic observations of cosmic ray induced air showers with
unprecedented energy resolution and angular resolution.
In addition to a discussion of recent measurements of the
energy spectrum of cosmic rays, this talk will focus on first results
from stereoscopic data. These include a measurement of the primary
chemical composition, and a search for anisotropies in the cosmic ray
arrival distribution, with emphasis on the highest energies, where
previous experiments have observed clustering.
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