Grant: $1,725,000 - National Science Foundation - Aug. 17, 2009
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Award Description: The Study of Nuclear Physics with Intermediate Energy Probes Summary A major goal of present day hadronic physics is to understand the transition between the two experimentally verified quantum field theories that describe nuclear phenomena: perturbative Quantum Chromodynamics (pQCD) at small distances which is governed by gluon fields; and Chiral Perturbation Theory (ChPT) at larger distances which is governed by pion fields. The non-abelian nature of the strong interaction gives rise to a non-perturbative confinement regime at intermediate distances where more than 98% of the mass of normal matter is generated. The medium energy nuclear physics group at the University of South Carolina (USC) is playing a leadership role in some of the most pressing experiments seeking to broaden our understanding of the nuclear force in the confinement regime. The proposed activities focus on in-medium modifications of hadronic properties and baryon spectroscopy. Our research program uses multi GeV photon and electron beams at the world-class Thomas Jefferson National Accelerator Laboratory (JLab). The modification of hadron masses, decay widths, and form factors in the medium are theoretically predicted as a consequence of the partial restoration of chiral symmetry and/or many body effects. Experimental observations of such phenomena are potentially transformative in the way we view interactions in nuclear matter. Our recent JLab results on the properties of light vector mesons in nuclei (g7 experiment) have clearly ruled out any major medium effects for the rho meson and observed a substantial widening of the omega and phi meson in nuclei. The approved high statistics follow-up run will allow further precise studies of the properties of these mesons decaying inside the nucleus. Onthe other hand, our experiments probe the structure of protons in the nuclear medium. The polarization-transfer observables from our most recent measurement are of unprecedented precision and show evidence for a medium modification of the elastic proton form factor, which is consistent with various predictions based on the Quark-Meson Coupling model (QMC). The induced polarization from this experiment provides us with the crucial means to constrain alternative interpretations. Measurements of excited states are needed to achieve a better understanding of how confinement works in nucleons. These excited states couple strongly to the meson-baryon continuum to form nucleon resonances of characteristic masses and decay widths. The USC group is a major player in Jefferson Labs baryon resonance program, which will provide high-precision, polarized and unpolarized, electro and photoproduction data for a global analysis effort...We are spearheading these efforts with several key experiments and by building and shaping international collaborations with theorists. The total N to (1232) cross section at low Q2 is predicted to be dominated by the longitudinal coupling to the meson cloud. In a low Q2 (< 0.1 GeV2) experiment we propose to study the pion cloud and to extract first transition form factors. At higher Q2 we have analyzed and are proposing to measure N to N* transition form factors in the most interesting kinematic regime where the transition from the constituent quark mass to the current quark mass is steepest. With single and double polarization measurements off the nucleon throughout the entire resonance region we will pin down resonant and non-resonant contributions. Moreover, through hyperon-kaon and sequential decay channels we are investigating new avenues to search for missing non-exotic resonances.The broader impact of the activities is apparent in the areas of student training, and the attraction and retention of students in scientific research. Our group has a strong record in the training of scientific personnel at the undergraduate, graduate, and postgraduate levels. We have created new opportunities for students to exchange experiences and scientifi
Project Description: As defined in the Award Description field.
Jobs Summary: Postdoctoral Research Associates Graduate Students Professor Summer Salary (Total jobs reported: 6)
Project Status: Not Started
This award's data was last updated on Aug. 17, 2009. Help expand these official descriptions using the wiki below.