Technical description: This award supports a program of research in experimental hadronic physics by the Arizona State University Meson Physics Group which will yield information crucial to achieving a better understanding of how hadrons are composed of quarks by providing a large data set detailing the excitation spectra of key two- and three-quark systems. In particular, the Meson Physics Group at Arizona State University will study the excitations of the nucleon, Cascade, and Omega baryons, as well as the excitations of gluonic flux tubes within mesons. The polarization data that the group will provide for the nucleon are essential for addressing one of the NSAC/OMB milestones for hadronic physics, and the ASU group is uniquely positioned to provide that data. The group is also participating in a conditionally approved experiment that will use the CLAS12 detector under construction at Jefferson Lab to produce and discover excited baryon states of the Cascade and Omega using quasi-real incident photons. The data to be obtained will further detail the excitations of three-quark systems and complements work being done by the group on excited nucleons. The Meson Physics Group at Arizona State University also will work with the GlueX detector, currently under construction in Hall D at Jefferson Lab, in order to search gluonic excitations within mesons of masses up to 2.5 GeV. The ASU group will assume primary responsibility for building a triplet polarimeter to directly measure the Hall D photon beam polarization. The results of these investigations will be broadly disseminated through conference presentations and refereed publications, and will be archived in public databases.
Broader significance and importance: No comprehensive theoretical description of how the nucleus of the atom is built from quarks can be achieved without a solid knowledge of the excited states. The data obtained from Arizona State University Meson Physics Group will further inform and test theoretical models used to understand the structure of matter that is comprised of quarks. In addition to potential discoveries in, and advancement of, the understanding of nuclear physics, the work to be supported will provide instruction and mentoring in science and technology to undergraduate and graduate students, as well as to a postdoctoral research associate. The triplet polarimeter to be built will enhance the precision reached for experiments conducted in Hall D at JLab as well as those using the photon beam at Mainz, resulting in important improvements in the infrastructure of those laboratories.
