paper

The -dependence of the generalised Gerasimov-Drell-Hearn integral for the deuteron, proton and neutron

arXiv:hep-ex/0210047 · doi:10.1140/epjc/s2002-01118-x

Abstract

The Gerasimov-Drell-Hearn (GDH) sum rule connects the anomalous contribution to the magnetic moment of the target nucleus with an energy-weighted integral of the difference of the helicity-dependent photoabsorption cross sections. The data collected by HERMES with a deuterium target are presented together with a re-analysis of previous measurements on the proton. This provides a measurement of the generalised GDH integral covering simultaneously the nucleon-resonance and the deep inelastic scattering regions. The contribution of the nucleon-resonance region is seen to decrease rapidly with increasing . The DIS contribution is sizeable over the full measured range, even down to the lowest measured . As expected, at higher the data are found to be in agreement with previous measurements of the first moment of . From data on the deuteron and proton, the GDH integral for the neutron has been derived and the proton--neutron difference evaluated. This difference is found to satisfy the fundamental Bjorken sum rule at GeV.

12 pages, 10 figures

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