The southern Pierre Auger Observatory is a 3000 square km hybrid cosmic ray detector located near Malargüe, Argentina. It consists of an array of 1600 water Cherenkov surface detectors together with four fluorescence detector sites, and is now fully completed and commissioned. This award will enable a research program focused on maximizing the scientific payoff from this detector. Key scientific questions that this group is attempting to address include: [1] What astrophysical objects produce the highest energy cosmic rays? [2] What constraints can be derived on Galactic and extragalactic magnetic fields from observations of cosmic rays? [3] What is the composition of the highest energy cosmic rays? [4] Are the interactions of the cosmic ray primaries consistent with existing models of high-energy interactions, or are there hints of new particle physics?
One area of emphasis in the group's data analysis includes studies of the effect of Galactic magnetic fields on cosmic ray arrival directions and the implications of this for Galactic field models, cosmic ray origins, and composition. Another area of study is the distribution of the depth of shower maximum and related shower variables as probes of cosmic ray composition and interactions. They are also working on the study of microwave bremsstrahlung from air showers as a possible new detection technique that would enable 24/7 fluorescence-like measurements.
The group is involved in outreach efforts to central Ohio high school students, which has contributed to student interest in pursuing college degrees in STEM disciplines. The Auger project is truly international, and contributes to international cooperation and understanding in the sciences.
Our research uses the Pierre Auger Observatory, located near Malargue, Argentina, to address questions concering the origin of the highest energy cosmic rays. Auger is an array of particle detectors roughly the size of the state of Rhode Island. Cosmic rays are subatomic particles accelerated to high energies by astrophysical objects. These cosmic rays interact with the Earth's atmospherre and produce a shower of lower enegy particles that can be detected both as a brief glow in the atmosphere and on the ground. By studying the characteristics of these showers, we can infer the properties of the original cosmic ray. We have studies the distribution of the depth at which the shower reaches its maximum size in the atmosphere. This depends on the type of particle and on its 'cross section', or how quickly it interacts upon entering the atmosphere. We find that as the energy increases the cross section appears to increase, which means the interaction occurs higher in the atmosphere. We also find that the type of particle does not vary widely in terms of the atomic number of the nuclei that form the mixture we observe. We have been working to understand what addtional data would be required to improve our understanding of these showers. The collaboration is pursuing an upgrade of the detector that would add additional detectors to the ground array to better determine the composition of each event, rather than from the variations between different events as we have done. We are helping to design new electronics for this upgrade of the experiment. Our group participates in acitvities to encourage young people to pursue an interest in science, including summer workshops for middle school and high school girls to maintain their interest in science at this critical stage.
