The Origin of the Highest Energy Particles

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AST-0071235Olinto, Angela V.The Origin of the Highest Energy ParticlesThe goal of this project is to conduct theoretical investigations into the origin of the highest energy cosmic rays (UHE cosmic rays, with E 5x 1019 eV). Using plausible scenarios for the production and propagation of these energetic particles (ranging from young neutron star winds to AGNs), Olinto and co workers will study several types of acceleration models and also model the propagation of different types of particles which may make up the UHE cosmic rays. Using these different models, they will generate predictions (of for example energy spectrum and relative isotropy) for comparison with the data obtained by such experiments as the Pierre Auger Project, the High Resolution Fly's Eye, the Japanese Telescope Array, and the OWL-Airwatch experiment.Occasionally a subatomic particle enters the atmosphere with so much energy that it produces a giant cascade of many tens of billions of secondary particles which can be observed by very large detectors on Earth. The particles that produce these giant air showers have been accelerated to far greater energies than can be achieved with terrestrial machines indicating incredibly powerful astronomical accelerators previously unforeseen. The explanation for the origin of these highestenergy particles remains unclear with a number of possibilities being proposed and constrained as the observations accumulate. The possibility that these particles come from the edge of the observable Universe is limited by the presence of the microwave background that fills all of space and degrades the energy of such high energy particles. The microwave background limits the location of these fantastic cosmic accelerators to relatively nearby in cosmological terms. The most plausible proposals range from supermassive black holes in centers of nearby galaxies to decaying particles left over from the Big Bang. The goal of this project is to try and find the answer by studying most plausible proposals in detail and model aspects of the propagation from source to Earth. Propagation studies will be intimately related to the knowledge of magnetic fields in the largest scales presently observed and particle physics models of interactions at the highest energies. Among plausible sources, we will investigate many models ranging from the most nearby possibility that these particles are iron accelerated in young neutron stars in the disk of our own Galaxy to the possible effects of large extra-dimensions on the physics of ultra-high energy cosmic rays. Funding for this project is provided by the NSF program for Extragalactic Astronomy & Cosmology (AST/EXC) and the Division of Physics Theoretical Physics Program.***