Hall A Proposal to JLab PAC 24 April 28 , 2003

We propose a measurement of double-polarization observables in the d(~e, e′~ p) reaction to investigate the spin structure of the deuteron. The individual components P ′ x and P ′ z, measured in parallel kinematics and in a broad range of pm, will reveal the dynamics of the deuteron spin structure and the manifestation of the D-state component in the deuteron ground-state wave-function. This will show to what extent the deuteron can be used as a neutron target. In contrast, the P0 y and the P ′ x/P ′ z ratio will mirror the underlying spindependent reaction mechanism. When using the P ′ x/P ′ z ratio to extract information on the electric form-factors, modern models surprisingly suggest that the D-state has little effect even at high missing momenta, while the effects from the spin-dependent reaction mechanism are enormous. A detailed study of these is extremely important to learn when the deuteron can be used as an effective neutron target, and also for the few-body physics. We will measure the cross-sections and the recoil polarization components P ′ x , P ′ z, and P0 y as functions of pm. Consequently, we will be able to extract the individual structure functions fL, fT, f n LT, f ′ t LT, and f ′ l T in the corresponding region of pm. The experiment requires a 70μA polarized beam at 0.845GeV and 3.2GeV, and the standard HRS configuration of Hall A with FPP capability. We request 243 hours of beam time.