This proposal requests continued funding for the Rutgers University group studying experimental Ultra High Energy Cosmic Ray physics. The group is working on the High Resolution Fly's Eye (HiRes) Experiment and the Telescope Array (TA) Experiment.
The questions about how the highest energy cosmic rays are accelerated and whether they are subject to a GZK cutoff, the sharp curtailment of the cosmic ray spectrum due to pion production in interactions between the cosmic rays and photons of the cosmic microwave background radiation, are among the most important topics in physics today. The aim of HiRes is to try to answer these questions by measuring the spectrum and composition of cosmic rays and, through searching for anisotropy in their pointing directions, identify their sources. The spectrum measured by the Rutgers group on HiRes is the best observation of the "ankle" of the cosmic ray spectrum. Other HiRes results include evidence for the transition between galactic and extragalactic sources.
The successor to HiRes is the TA experiment, now being deployed in Millard County, Utah. This will have an order of magnitude larger aperture than HiRes and will concentrate on the high end of the cosmic ray energy spectrum. TA has been funded by both the NSF and Kakenhi, the Japanese funding agency.
On Broader Impacts, the group will continue and increase a long-standing effort in involving research students from groups underrepresented in physics, and outreach to middle and high school students in New Jersey. They will also take part in the activities of the Cosmic Ray Visitor's Center now being developed in Delta, Utah, near the site to the TA experiment.
