Non-Strange Pseudoscalar Photoproduction from the Proton

Dr. Michael Dugger
Arizona State University,
Tempe, AZ 85287-1504, USA

Since the proton is made up of quarks, the proton has an excitation spectrum that can reveal details of the forces between the quarks. In much the same way that atomic spectroscopy yields information about the excited states of atoms, baryon spectroscopy explores the excitation spectra of excited baryons (which includes the proton). The excitation spectrum of the proton is comprised of many broad overlapping resonances, which makes investigations of these resonances challenging. The photoproduction of non-strange pseudoscalar photoproduction provides an excellent tool in helping deconvolve the spectrum. Since the beginning of this new millennium, much progress has been made in measuring pion, h and h' photoproduction from the proton. In addition to differential cross section data, there have been a comparatively smaller number of polarization measurements for meson photoproduction. However, these polarization measurements, if they exist at all, only cover the energy range up to about Eg  = 1.5 GeV. I will present exam- ples of preliminary Jefferson Lab CLAS data on beam asymmetry for the p+, p0, h and h' mesons for energies up to about Eg = 2.0 GeV. I will also discuss how the new measurements, along with newly taken target polarization data, will be useful in understanding the structure and excited states of the proton. 

This work is supported by the U.S. National Science Foundation.