Barry Preedom, Distinguished Professor Emeritus

Intermediate Energy Nuclear Physics. Studies of photonuclear reactions including scalar and vector meson photoproduction using polarized gamma rays.

Our research program involves basic experimental nuclear physics measurements at two accelerator labortories. The present research is performed at the Laser Electron Gamma source (LEGS) at the National Synchrotron Light Source at Brookhaven National Laboratory and at the Continuous Electron Beam Accelerator Facility (CEBAF) using the Large Acceptance Spectrometer (CLAS) at the Thomas Jefferson National Accelerator Facility in Newport News, Va. The LEGS facility produces tagged polarized gamma rays with energies up to 470 MeV by the backscattering of laser light from the 2.8 GeV electrons stored in the synchrotron. The CLAS is a superconducting toroidal spectrometer with a large solid angle for studying the structure of the nucleon using medium energy photons, including the use of polarization observables. This information is critical for understanding Quantum Chromodynamics in the non-perturbative region. There are several reasons for the present intense world-wide interest in these studies of the nucleon. These include the fact that the nucleon structure now appears considerably more complex and interesting than simple quark-model predictions made it appear until about a decade ago. Another reason is that these experiments were simply not possible before. One of the new tools is the SPHICE target, a unique polarized hydrogen deuteride target that will be used at LEGS and CLAS. This target became operational at LEGS in November, 1999.

Selected Publications

"Exclusive electroproduction of phi mesons at 4.2 GeV", K. Lukashin, etal, (The CLAS Collaboration), Phys. Rev., C63, 065205 (2001); C64, 059901(E) (2001).

"The N->Delta Transition and Proton Polarizabilities from Measurements of p(gamma,gamma), p(gamma,pi0), and p(gamma,pi+) with polarized gamma rays", G. Blanpied, etal,. (The LEGS Collaboration), Phys. Rev., C64, 025203 (2001); 029902(E) (2001).

"Electroproduction of the Lambda(1520) hyperon", S.P. Barrow, etal., (The CLAS Collaboration), Phys. Rev., C64, 044601 (2001).

"Photoproduction of the rho0 meson on the proton at large momentum transfer", M. Battaglieri, etal., (The CLAS Collaboration), Phys. Rev. Letters, 87, 172002 (2001).

"First Obervation of Exclusive Deeply Virtual Compton Scattering in Polarized Electron Beam Asymmetry Measurements", S. Stepanyan, etal., (The CLAS Collaboration), Phys. Rev. Letters, 87, 182002 (2001).