The 18th International Symposium on Spin Physics

October 6-11, 2008
University of Virginia
Charlottesville, VA USA

View Abstract

First Name Craig
Last Name Thorn
Affiliation BNL
Title Precision polarimetry of solid HD and the convergence of the GDH integral
Topic Oral
Abstract of 200 words or less
The development of a highly-polarized, frozen-spin HD target and of a
high accuracy, crossed-coil NMR polarimeter at LEGS have produced new measurements of inclusive p production with polarized photon beams covering the D(1232) resonance on both H and D of the spin-difference cross sections entering the Gerasimov-Drell-Hearn (GDH) sum rule. While our charged-p data from H agree with earlier Mainz data, our p0 results near the peak of the D reveal a different angular distribution than assumed in Mainz analyses. As a result, our p0 contribution to the GDH sum rule is 18 mb less than the Mainz result for H, obviating the need for any speculative high-energy components. We will discuss these results, with emphasis on the techniques and accuracy of the target polarization determination.