Welcome to the Columbia University HiRes page!
One of today's great scientific mysteries is the origin of cosmic rays particles with energies beyond 1020 eV (about 20 Joules), the highest energy particles observed in the universe. The existence of particles at these energies continues to challenge our imagination: where do they come from, how are they accelerated to these energies, and how can they travel astronomical distances without substantial loss of energy?
The HiRes Air Fluorescence Experiment
The goal of the High Resolution Fly's Eye (HiRes) Experiment in Dugway, Utah, is to measure the energy spectrum, the arrival direction, and the composition of cosmic rays above 1018 eV.
HiRes is an air fluorescence detector consisting of a large number of focusing mirrors that image fluorescence light from distant air shower cascades onto arrays of photomultiplier tubes.
Several quantities that can help to answer these questions are accessible to experiment: the flux of cosmic rays, their composition, and, above about 1020 eV, when deflections in magnetic fields become small, their arrival direction. In operation since 1999, the HiRes experiment has been designed with exactly these measurements in mind.
For more details on the HiRes experiment and the physics of ultrahigh energy cosmic rays, please read on.
