Study of the nucleon using polarized photon beams and polarized targets

University South Carolina Research Foundation, Columbia SC

Investigators

Abstract

This research uses photonuclear reactions to investigate the properties of the nucleon through the production of mesons and nucleon resonances using polarized photon beams and polarized targets. The Laser Electron Gamma Source (LEGS) provides a polarized beam with photons having energies up to 470 MeV obtained by the backscattering of polarized laser light from 2.8 GeV electrons stored in the National Synchrotron Light Source. With the successful development of the frozen, polarized HD target SPHICE which allows independent polarization of the proton and the deuteron and with the successful operation of the SASY (Spin ASYmmetry) detector, this research will perform detailed double polarization measurements on both the proton and the neutron. Combining SPHICE and SASY with the high quality polarized photon beam at LEGS, the experimental program will measure the differential cross sections for both neutral and charged pion production. The photon, being the quantum of the electromagnetic field, can interact with both the distribution of electric charges in the nucleon as well as the magnetic-field-producing charged quark currents within the nucleon. Because the polarization of the photon is determined by the polarization of the laser beam, linear and circular polarizations can be used. Since the nucleon has a magnetic moment that can be oriented by manipulating the spin of the nucleon, spin-dependent photoproduction quantities can determined to accuracies never before possible.