Search Results (8 total)

We present a measurement of the spin-dependent cross sections for the ³He→(e→,e^′)X reaction in the quasielastic and resonance regions at a four-momentum transfer 0.1≤Q²≤0.9  GeV². The spin-structure functions have been extracted and used to evaluate the nuclear Burkhardt-Cottingham and extended Gerasimov-Drell-Hearn sum rules for the first time. The data are also compared to an impulse approximation calculation and an exact three-body Faddeev calculation in the quasielastic region.

We have measured the transverse asymmetry A_T^' in the quasielastic ³He→(e→,e^') process with high precision at Q² values from 0.1 to 0.6  (GeV/c)². The neutron magnetic form factor G_Mⁿ was extracted at Q² values of 0.1 and 0.2  (GeV/c)² using a nonrelativistic Faddeev calculation which includes both final-state interactions (FSI) and meson-exchange currents (MEC). Theoretical uncertainties due to the FSI and MEC effects were constrained with a precision measurement of the spin-dependent asymmetry in the threshold region of ³He→(e→,e^'). We also extracted the neutron magnetic form factor G_Mⁿ at Q² values of 0.3 to 0.6  (GeV/c)² based on plane wave impulse approximation calculations.

The generalized forward spin polarizabilities γ₀ and δ_LT of the neutron have been extracted for the first time in a Q² range from 0.1 to 0.9  GeV². Since γ₀ is sensitive to nucleon resonances and δ_LT is insensitive to the Δ resonance, it is expected that the pair of forward spin polarizabilities should provide benchmark tests of the current understanding of the chiral dynamics of QCD. The new results on δ_LT show significant disagreement with chiral perturbation theory calculations, while the data for γ₀ at low Q² are in good agreement with a next-to-leading-order relativistic baryon chiral perturbation theory calculation. The data show good agreement with the phenomenological MAID model.

We have measured the spin structure functions g₁ and g₂ of ³He in a double-spin experiment by inclusively scattering polarized electrons at energies ranging from 0.862 to 5.058 GeV off a polarized ³He target at a 15.5° scattering angle. Excitation energies covered the resonance and the onset of the deep inelastic regions. We have determined for the first time the Q² evolution of Γ₁(Q²)=∫₀¹g₁(x,Q²)dx, Γ₂(Q²)=∫₀¹g₂(x,Q²)dx, and d₂(Q²)=∫₀¹x²[2g₁(x,Q²)+3g₂(x,Q²)]dx for the neutron in the range 0.1≤Q²≤0.9  GeV² with good precision. Γ₁(Q²) displays a smooth variation from high to low Q². The Burkhardt-Cottingham sum rule holds within uncertainties and d₂ is nonzero over the measured range.

A high precision measurement of the transverse spin-dependent asymmetry A_T^′ in ³He→(e→,e^′) quasielastic scattering was performed in Hall A at Jefferson Lab at values of the squared four-momentum transfer, Q², between 0.1 and 0.6 (GeV/c)². A_T^′ is sensitive to the neutron magnetic form factor, G_Mⁿ. Values of G_Mⁿ at Q²=0.1 and 0.2 (GeV/c)², extracted using Faddeev calculations, were reported previously. Here, we report the extraction of G_Mⁿ for the remaining Q² values in the range from 0.3 to 0.6 (GeV/c)² using a plane-wave impulse approximation calculation. The results are in good agreement with recent precision data from experiments using a deuterium target.

We present data on the inclusive scattering of polarized electrons from a polarized ³He target at energies from 0.862 to 5.06 GeV, obtained at a scattering angle of 15.5°. Our data include measurements from the quasielastic peak, through the nucleon resonance region, and beyond, and were used to determine the virtual photon cross-section difference σ_1/2-σ_3/2. We extract the extended Gerasimov-Drell-Hearn integral for the neutron in the range of four-momentum transfer squared Q² of 0.1–0.9   GeV².

We present the first precision measurement of the spin-dependent asymmetry in the threshold region of ³H→e(e→,e^′) at Q² values of 0.1 and 0.2 (GeV/c)². The agreement between the data and nonrelativistic Faddeev calculations which include both final-state interactions and meson-exchange current effects is very good at Q²  =  0.1 (GeV/c)², while a small discrepancy at Q²  =  0.2 (GeV/c)² is observed.

We have measured the transverse asymmetry A_T^′ in ³He→(e→,e^′) quasielastic scattering in Hall A at Jefferson Laboratory with high precision for Q² values from 0.1 to 0.6 (GeV/c)². The neutron magnetic form factor G_Mⁿ was extracted based on Faddeev calculations for Q²  =  0.1 and 0.2 (GeV/c)² with an experimental uncertainty of less than 2%.