Pair polarimeter for high-energy linearly polarized photons

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Intellectual Merits: In spite of 40 years of history, high energy photon polarimetry is an undeveloped field. At JLab energies all known methods have low analyzing power, and the absolute accuracy is below that required for the approved and anticipated physics programs. Currently, the only way to estimate the degree of photon polarization in Hall B is by fitting theoretical calculations to the collimated photon energy spectrum. The JLab physics program in Hall B and planned Hall D will significantly benefit from this new polarimeter, which will significantly reduce a major systematic experimental error in all approved and some planned experiments. The proposed polarimeter will have an experimental asymmetry of approximately 1.7 (analyzing power 26%) for an energy range from a few tens of MeV up to several GeV. This implies that for a beam intensity of 106 photons per second, such as at the JLab, a 1% statistical accuracy of the polarization measurement will require less then one hour of data taking. The polarimeter is simple in construction, compact, and its costs will be lower than for polarimeters built according to any other available method. Three prototypes were built and tested at Duke, BNL, SPring8 and JLab. The analyzing power was determined to be 19.2% for equal-energy pairs and 11.9% for all events during the test run at the Spring-8. The polarimeter was applied at JLab Hall B g8b experiment and it worked as predicted, there was no problem with high beam intensity and reconstruction of the events. Since the budget is reduced for more then 90% the scope of the work will be limited only to the education of the students that will have assigned projects related to the polarimeter physics. Any work planned related to the research or development of the polarimeter will be no performed, because of the lack of the support. Broader Impact: The proposed research and education program could result in increased competitiveness of the NCCU physics and science programs, and improved conditions for the faculty and student recruitment. The integration between research and education could be expanded with new courses and research programs designed to enrich current curriculum and bring more students into the original research. However the limited funding will allow us only to develop student research projects that will create an ambient for enhancing undergraduate computational program in science department, and recently approved graduate program in physics. The most significant impact of the project will be in providing highly qualified work force with highly skilled minorities and socially underrepresented groups. The original research in the fields of nuclear and computational physics, and computer modeling, could increase production of more competitive students. Emerging scientific advances and opportunities could also provide flexibility in career choices, adequately prepare our students for further graduate studies, and highlight the job opportunities for our graduates. Furthermore, we expect that this program will stimulate continuing expansion of training for African American graduate and undergraduate students.