RUI: Studies of Strangeness, Baryon Structure and Exotic Atoms

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This project will address current problems in quark models of strongly interacting particles and a related topic in exotic atoms. One problem concerns the production of strange particles (sigma and lambda hyperons) and their antiparticles from collisions of protons and antiprotons. We will calculate in a quark model the cross-sections and spin observables for these reactions, and compare them to experiment and to meson-exchange calculations. Our goal is to determine the reaction mechanism and the unknown hyperon- antihyperon interaction. Another problem of contemporary interest is the contribution of strange quarks and antiquarks to the spin of the proton. We have proposed a model of polarized, intrinsic strangeness in the proton which we will further develop in order to test it against spin transfer data from the hyperon production experiments. A third problem is the asymmetry of different quark flavors (up, down, and strange) in the sigma hyperon, which we will calculate in a model in which mesons are coupled to quarks. Finally, we will calculate energy level shifts and widths in exotic atoms in order to learn about nucleon wave functions and elementary hadron-nucleon interactions. Research assistantships will be provided so that undergraduate students can collaborate in this program.