Spin-Momentum Correlations in Quasielastic Electron Scattering from Deuterium

Abstract

The spin-momentum correlation parameter A V ed was measured for the 2 H͑e, e 0 p͒n reaction for missing momenta up to 350 MeV͞c at Q 2 0.21 ͑GeV͞c͒ 2 for quasielastic scattering of polarized electrons from vector-polarized deuterium. The data give detailed information about the deuteron spin structure and are in good agreement with the results of microscopic calculations based on realistic nucleon-nucleon potentials and including various spin-dependent reaction mechanism effects. The experiment reveals in a most direct manner the effects of the D state in the deuteron ground-state wave function and shows the importance of isobar configurations for this reaction. DOI: 10.1103/PhysRevLett.88.102302 PACS numbers: 25.30.Fj, 21.45. +v, 24.70. +s, 27.10. +h The deuteron serves as a benchmark for testing nuclear theory. Observables such as its binding energy, static magnetic dipole and charge quadrupole moment, asymptotic D͞S ratio, and the elastic electromagnetic form factors place strong constraints on any realistic nuclear model. Its simple structure allows reliable calculations to be performed in both nonrelativistic and relativistic frameworks [1 -6]. Such calculations are based upon state-of-the-art nucleon-nucleon (NN) potentials [7][8][9][10], and the resulting ground-state wave function is dominated by the S state, especially at low relative proton-neutron momentum p in the center of mass system. Because of the tensor part of the NN interaction a D-state component is generated (see, e.g., [5,11]). The models predict that the S-and D-state components strongly depend on p and are sensitive to the repulsive core of the NN interaction at short distances [5].Traditionally, the spin structure of the deuteron has been studied through measurements of the tensor analyzing power T 20 [12][13][14][15][16][17][18] in elastic electron-deuteron scattering. Complementary information can be obtained by electrodisintegration studies in the region of quasielastic scattering. In the 2 H͑e, e 0 p͒n reaction, energy n and three-momentum q are transferred to the nucleus and the nuclear response can be mapped as a function of missing momentum p m and missing energy. Here, p m ϵ q 2 p f and p f represents the momentum of the ejected proton. In the planewave impulse approximation (PWIA) the neutron is a spectator only during the scattering process, and p m is equal to the initial proton momentum in the deuteron, while the missing energy equals the binding energy. In this way the ͑e, e 0 p͒ reaction has been employed to probe the proton inside the deuteron for momenta up to 1.0 GeV͞c [19][20][21].To enhance the sensitivity to the spin structure of the deuteron, spin dependent observables in quasielastic scattering can be used [5,22,23]. The polarization of a proton P p z inside a deuteron with a vector polarization P d 1 , is given by [24]where P S and P D , respectively, represent the S-and D-state probability densities of the ground-state wave function. Note that the polarization of a nucleon in the D state is opposite to that of...

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