Measurement of the Gerasimov-Drell-Hearn Integral at low on the Neutron and Deuteron

We propose a precision measurement at low momentum transfer ( GeV ) of the Gerasimov-Drell-Hearn integral for the deuteron using the Hall B CLAS detector. By combining these data with the proton data taken under similar conditions (approved E03-006) we can extract the GDH integral on the neutron. These data will provide a benchmark for neutron Chiral Perturbation Theory ( PT) calculations. Also, at the very low of the proposed experiment, extrapolation to will permit a check of the (real photon) GDH sum rule. Due to the complexity of nuclear medium effects, extraction from both the deuteron and He is necessary to have confidence in neutron data at very low . An experiment [1] with the same goals as this proposal, but using a He target was approved in Hall A. In addition, as recently emphasized [2], the GDH sum for the deuteron is a fascinating quantity in its own right and presents a significant test of our present understanding of the properties of few-body nuclei. The experimental conditions will be the same as those of approved experiment E03-006, except for the content of the target cell. The combined data set will therefore provide a self-consistent test of the Bjorken sum, which is believed to be the best quantity to measure in the context of linking the partonic and hadronic descriptions of the strong interaction. To perform this measurement, we request 30 days of beam time.