The 18th International Symposium on Spin Physics

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

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First Name Craig
Last Name Thorn
Email
Affiliation BNL
Co-Authors
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.