[en] Measurements were made of the proton and deuteron spin structure functions g₁^p and g₁^d at beam energies of 29.1, 16.2, and 9.7 GeV, and g₂^p and g₂^d at a beam energy of 29.1 GeV. The integrals Λ_p = ∫₀¹ g₁^p (x, Q²)dx and Λ_d = ∫₀¹ g₁^d(x, Q²)dx were evaluated at fixed Q² = 3 (GeV/c)² using the 29.1 GeV data to yield Λ_p = 0.127 ± 0.004(stat.) ± 0.010(syst.) and Λ_d = 0.041 ± 0.003 ± 0.004. The Q² dependence of the ratio g₁/F₁ was studied and found to be small for Q² > 1 (GeV/c)². Within experimental precision the g₂ data are well-described by the twist-2 contribution, g₂^WW. Twist-3 matrix elements were extracted and compared to theoretical predictions. The asymmetry A₂ was measured and found to be significantly smaller than the positivity limit √R for both proton and deuteron targets. A₂^p is found to be positive and inconsistent with zero

[en] The charge and magnetic elastic form factors of the neutron, G_En(Q²) and G_Mn(Q²), have been measured in the four-momentum transfer range 1.75 < Q² < 4.00 (GeV/c )² using a Rosenbluth separation. These measurements constitute part of performed at the End Station A experiment NE11 which was facilities at the Stanford Linear Accelerator Center in the winter of 1989. The results show that G_Mn(Q²)/μ_n, G_D(Q₂) is consistent with unity, where μ_n, is the neutron anomalous magnetic moment, and G_D(Q²) = (1.0 + Q²/0.71) ^-2, is the empirical dipole formula. The results for (G_En(Q²)/G_D(Q²)) are consistent with zero within errors. The extraction of the neutron electromagnetic form factors from deuterium cross sections is a model dependent procedure because of the Fermi momentum of the bound nucleons. In addition to the smeared quasielastic cross section, there is an inelastic tail due to pion production which extends into the quasielastic region. This tail is significant and must be subtracted to measure the neutron form factors. An extensive study has been made on the effect of the modeling of this tail on the measured form factors using different Fermi smearing models, off-mass-shell corrections, and deuteron wave functions. The off-mass-shell-effects were the largest, but still smaller than the experimental error. Comparisons were made with many theoretical models. Measurements were also obtained of the Δ(1232) resonance transition form factors in the range 1.6 < Q² < 6.75 (GeV/c)²

[en] Measurements have been made of the proton and deuteron spin structure functions, g₁^p at beam energies of 29.1, 16.2, and 9.7 GeV, and g₂^p and g₂^d at a beam energy of 29.1 GeV. The integrals Γ_p = ∫₀¹ g₁^p (x, Q²)dx and Γ_d = ∫₀¹ g₁^d(x, Q²)dx have been evaluated at fixed Q² = 3 (GeV/c)² using the 29.1 GeV data to yield Γ_p = 0.127 ± 0.004(stat.) ± 0.010(syst.) and Γ_d = 0.041 ± 0.003 ± 0.004. The Q² dependence of the ratio g₁/F₁ has been studied and is found to be small for Q² > 1 (GeV/c)². Within experimental precision, the g₂ data are well-described by the twist-2 contribution, g₂^ww. Twist-3 matrix elements have been extracted and are compared to theoretical predictions. The asymmetry A₂ has also been measured and is found to be significantly smaller than the positivity limit √R for both targets A₂^p is found to be positive and inconsistent with zero

[en] New measurements have been made of the proton and deuteron spin structure functions, g^p₁ and g^d₁, using deep-inelastic scattering of longitudinally polarized electrons from polarized NH₃ and ND₃ targets. The data span the kinematic range 0.029< x<0.8 and Q²<10 (GeV/c)². The integrals Γ_p=∫¹₀g^p₁(x,Q²)dx and Γ_d=∫¹₀g^d₁(x,Q²)dx have been evaluated at fixed Q²=3 (GeV/c)² to yield Γ_p=0.127±0.004(stat.)±0.010(syst.) and Γ_d=0.041±0.003±0.004. Both measurements are well-below the Ellis-Jaffe predictions

[en] Quasielastic e-d cross sections have been measured over a large is an element of range for Q²=1.75, 2.50, 3.25 and 4.00 (GeV/c)². Rosenbluth separations have been made on the cross sections to obtain R_L and R_T and the neutron form factors, G_En and G_Mn, have been extracted via model dependent methods. The sensitivity of the form factor results to various model assumptions has been studied. The results for G_Mn are consistent with form factor scaling, while G_En is consistent with zero. Comparisons are made to several theoretical predictions. (author)

[en] The neutron electromagnetic form factors G_En and G_Mn, which reflect the charge and magnetization distributions within the neutron, are of fundamental importance for understanding nucleon structure, and are necessary for calculations of processes involving the electromagnetic interaction with complex nuclei. These quantities are functions of Q², the four-momentum transfer squared. SLAC experiment NE11 has measured these form factors out to a Q² of 4.0 (GeV/c)² with high precision, and the results have been recently published. This paper provides some additional details on the extraction of G_Mn and G_En from the NE11 measurements. Several formalisms have been developed over the years which attempt to understand the nucleon form factors using basic physical principles. Vector Meson Dominance (VMD) models are based on superpositions of photon couplings to various vector mesons. These models generally involve free parameters which are fit to form factor data at low Q², and are not expected to be valid at high Q². For asymptotically large Q², dimensional scaling methods and perturbative Quantum Chromodynamics (pQCD) predict form factor behavior at large Q², but they do not make absolute magnitude predictions. To describe the form factor behavior at intermediate values of Q², a hybrid model by Gari and Kruempelmann (GK) uses VMD constraints at low Q₂ and pQCD constraints at high Q². Free parameters in the model are adjusted to fit existing form factor data. Other approaches include the use of QCD sum rules to make absolute predictions, diquark models, and relativistic constituent quark models

[en] Measurements of inclusive electron-scattering cross sections using hydrogen and deuterium targets in the region of the Δ(1232) resonance are reported. A global fit to these new data and previous data in the resonance region is also reported for the proton. Transition form factors have been extracted from the proton cross sections for this experiment over the four-momentum transfer squared range 1.64< Q²<6.75 (GeV/c)² and from previous data over the range 2.41< Q²<9.82 (GeV/c)². The results confirm previous reports that the Δ(1232) transition form factor decreases more rapidly with Q² than expected from perturbative QCD. The ratio of σ_n/σ_p in the Δ(1232) resonance region has been extracted from the deuteron data for this experiment in the range 1.64< Q²<3.75 (GeV/c)² and for a previous experiment in the range 2.4< Q²<7.9 (GeV/c)². A study has been made of the model dependence of these results. This ratio σ_n/σ_p for Δ(1232) production is slightly less than unity, while σ_n/σ_p for the nonresonant cross sections is approximately 0.5, which is consistent with deep inelastic scattering results. thinsp copyright 1998 The American Physical Society

[en] The structure functions g₁^p and g₁ⁿ have been measured over the range 0.014 < x < 0.9 and 1 < Q² < 40 GeV² using deep-inelastic scattering of 48 GeV longitudinally polarized electrons from polarized protons and deuterons. We find that the Q² dependence of g₁^p (g₁ⁿ) at fixed x is very similar to that of the spin-averaged structure function F₁^p (F₁ⁿ). From a NLO QCD fit to all available data we find Γ₁^p - Γ₁ⁿ = 0.176 ± 0.003 ± 0.007 at Q² = 5 GeV², in agreement with the Bjorken sum rule prediction of 0.182 ± 0.005

[en] Quasielastic e-d cross sections have been measured at forward and backward angles. Rosenbluth separations were done to obtain R_L and R_T at Q²=1.75, 2.50, 3.25, and 4.00 (GeV/c)². The neutron form factors G_En and G_Mn have been extracted using a nonrelativistic model. The sensitivity to deuteron wave function, relativistic corrections, and models of the inelastic background are reported. The results for G_Mn are consistent with the dipole form, while G_En is consistent with zero. Comparisons are made to theoretical models based on vector meson dominance, perturbative QCD, and QCD sum rules, as well as constituent quarks

[en] New measurements are reported on the deuteron spin structure function g₁^d. These results were obtained from deep inelastic scattering of 48.3 GeV electrons on polarized deuterons in the kinematic range 0.01 < x < 0.9 and 1 < Q² < 40 (GeV/c)². These are the first high dose electron scattering data obtained using lithium deuteride (⁶Li²H) as the target material. Extrapolations of the data were performed to obtain moments of g₁^d, including Γ₁^d, and the net quark polarization Δ Σ