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We report measurements of the proton form factors [ital G][sub [ital E]][sup [ital p]] and [ital G][sub [ital M]][sup [ital p]] extracted from elastic scattering in the range 1[le][ital Q][sup 2][le]3 (GeV/[ital c])[sup 2] with total uncertainties [lt] 15% in [ital G][sub [ital E]][sup [ital p]] and [lt] 3% in [ital G][sub [ital M]][sup [ital p]]. Comparisons are made to theoretical models, including those based on perturbative QCD, vector-meson dominance, QCD sum rules, and diquark constituents in the proton. The results for [ital G][sub [ital E]][sup [ital p]] are somewhat larger than indicated by most theoretical parametrizations, and the ratios of the Pauli and Dirac form factors [ital Q][sup 2]([ital F][sub 2][sup [ital p]]/[ital F][sub 1][sup [ital p]]) are lower in value and demonstrate a weaker [ital Q][sup 2] dependence than those predictions. A global extraction of the elastic form factors from several experiments in the range 0.1 [lt] [ital Q][sup 2] [lt] 10 (GeV/[ital c])[sup 2] is also presented.

We report results on a precision measurement of the ratio R=σ_L/σ_T in deep inelastic electron-nucleon scattering in the kinematic range 0.2≤x≤0.5 and 1≤Q^2≤10 (GeV/c)^2. Our results show, for the first time, a clear falloff of R with increasing Q^2. Our R results are in agreement with QCD predictions only when corrections for target mass effects and some additional higher twist effects are included. At small x, the data on R favor structure functions with a large gluon contribution. We also report results on the differences R_A-R_D and the cross section ratio σ^A/σ^D between Fe and Au nuclei and the deuteron. Our results for R_A-R_D are consistent with zero for all x, Q^2 indicating that possible contributions to R from nuclear higher twist effects and spin-0 constituents in nuclei are not different from those in nucleons. The ratios σ^A/σ^D from all recent experiments, at all x, Q^2 values, are now in agreement.

Cross sections for 180{degree} deuteron electrodisintegration have been measured near threshold for the {ital Q}{sup 2} range 1.21 to 2.77 (GeV/{ital c}){sup 2}. The data are compared to several nonrelativistic meson-nucleon and hybrid quark-hadron models. The data are in strong disagreement with the impulse approximation, indicating the importance of non-nucleonic degrees of freedom. None of the models are in good agreement with the data at all values of {ital Q}{sup 2}. The ratio {ital W}{sub 1}/{ital W}{sub 2} of inelastic structure functions has been extracted using previous forward angle data and is found to decrease strongly near threshold, also indicating the importance of interaction effects.

Deuteron electrodisintegration cross sections near 180\ifmmode^\circ\else\textdegree\fi{} have been measured near breakup threshold for the four-momentum transfer squared ${\mathit{Q}}^{2}$ range 1.21--2.76 (GeV/c${)}^{2}$. Evidence for a change of slope in the cross section near ${\mathit{Q}}^{2}$=1 (GeV/c${)}^{2}$ has been obtained. The data are compared to nonrelativistic calculations, which predict a strong influence of meson-exchange currents. The data are also compared to a hybrid quark-hadron model. None of these calculations agrees with the data over the entire measured range of ${\mathit{Q}}^{2}$. The ratio of inelastic structure functions ${\mathit{W}}_{1}$(${\mathit{Q}}^{2}$,${\mathit{E}}_{\mathit{n}\mathit{p}}$)/${\mathit{W}}_{2}$(${\mathit{Q}}^{2}$,${\mathit{E}}_{\mathit{n}\mathit{p}}$) is extracted from the present results and previous forward angle data. No prediction is in good agreement with the deduced ratios at small relative energy ${\mathit{E}}_{\mathit{n}\mathit{p}}$.

Measurements of the deuteron elastic magnetic structure function B(${\mathit{Q}}^{2}$) are reported at squared four-momentum transfer values 1.20\ensuremath{\le}${\mathit{Q}}^{2}$\ensuremath{\le}2.77 (GeV/c${)}^{2}$. Also reported are values for the proton magnetic form factor ${\mathit{G}}_{\mathit{M}\mathit{p}}$(${\mathit{Q}}^{2}$) at 11 ${\mathit{Q}}^{2}$ values between 0.49 and 1.75 (GeV/c${)}^{2}$. The data were obtained using an electron beam of 0.5 to 1.3 GeV. Electrons backscattered near 180\ifmmode^\circ\else\textdegree\fi{} were detected in coincidence with deuterons or protons recoiling near 0\ifmmode^\circ\else\textdegree\fi{} in a large solid-angle double-arm spectrometer system. The data for B(${\mathit{Q}}^{2}$) are found to decrease rapidly from ${\mathit{Q}}^{2}$=1.2 to 2 (GeV/c${)}^{2}$, and then rise to a secondary maximum around ${\mathit{Q}}^{2}$=2.5 (GeV/c${)}^{2}$. Reasonable agreement is found with several different models, including those in the relativistic impulse approximation, nonrelativistic calculations that include meson-exchange currents, isobar configurations, and six-quark configurations, and one calculation based on the Skyrme model. All calculations are very sensitive to the choice of deuteron wave function and nucleon form factor parametrization. The data for ${\mathit{G}}_{\mathit{M}\mathit{p}}$(${\mathit{Q}}^{2}$) are in good agreement with the empirical dipole fit.

We report recent work on the extraction of R = {sigma}{sub L}/{sigma}{sub T} and the structure function F{sub 2} over a large kinematic range, which is based on a reanalysis of deep inelastic {var epsilon} {minus} p and {var epsilon} {minus} d scattering cross sections measured at SLAC between 1970 and 1985. All these data were corrected for radiative effects using improved versions of external and internal radiative correction procedures. The data from seven individual experiments were normalized to those from the recent high-precision SLAC experiment E140. We find that R{sub p} = R{sub d}, as expected in QCD. The value of R is higher than predicted by QCD even when target-mass effects are included. This difference indicates that additional dynamical higher-twist effects may be present. The structure functions F{sub 2}p and F{sub 2}d were also extracted from the full data sets of normalized cross sections using an empirical fit to R. These structure functions were then compared with data from the CERN muon scattering experiments BCDMS and EMC. We find that our data are consistent with the EMC data, if the latter are multiplied by a normalization factor of 1.07. No single, uniform normalization factor can be applied tomore » the BCDMS data that will bring them into agreement with the SLAC data in the region of overlap.« less

We report measurements of the proton form factors, G^p_E and G^p_M, extracted from elastic electron scattering in the range 1 ≤ Q^2 ≤ 3 (GeV/c)^2 with uncertainties of

The deuteron magnetic form factor B(${Q}^{2}$) has been measured at momentum transfers ${Q}^{2}$=1.21, 1.49, 1.61, 1.74, 1.98, 2.23, 2.48, 2.53, and 2.77 (GeV/c${)}^{2}$ at the Stanford Linear Accelerator Center by detection of electrons backscattered at 180\ifmmode^\circ\else\textdegree\fi{} in coincidence with recoiling deuterons at 0\ifmmode^\circ\else\textdegree\fi{}. The data for B(${Q}^{2}$) are found to decrease rapidly from ${Q}^{2}$=1.2 to 2 (GeV/c${)}^{2}$, then rise to a secondary maximum around ${Q}^{2}$=2.5 (GeV/c${)}^{2}$, in qualitative agreement with impulse-approximation calculations.

We report new results on a precision measurement of the ratio $R=\frac{{\ensuremath{\sigma}}_{L}}{{\ensuremath{\sigma}}_{T}}$ and the structure function ${F}_{2}$ for deep-inelastic electron-nucleon scattering in the kinematic range $0.2\ensuremath{\le}x\ensuremath{\le}0.5$ and $1\ensuremath{\le}{Q}^{2}\ensuremath{\le}10$ ${(\mathrm{G}\mathrm{e}\mathrm{V}/\mathit{c})}^{2}$. Our results show, for the first time, a clear falloff of $R$ with increasing ${Q}^{2}$. Our $R$ and ${F}_{2}$ results are in good agreement with QCD predictions only when corrections for target-mass effects are included.

We report new results on a precision measurement of the ratio R= σ L / σ T , and the structure function F 2 , for deep inelastic electron-nucleon scattering in the range 0.2≤×≤0.5 and 1≤Q 2 ≤10 (GeV/c) 2 . Our results show, for the first time, a clear falloff of R with increasing Q 2 . Our R and F 2 results are in good agreement with QCD predictions only when corrections for target mass effects are included.

We measured the differences in R=σ_L/σ_T and the cross-section ratio σA/σD in deep-inelastic electron scattering from D, Fe, and Au nuclei in the kinematic range 0.2≤x≤0.5 and 1≤Q^2≤5 (Gev/c)^2. Our results for R^A-R^D are consistent with zero for all x and Q^2, indicating that possible contributions to R from nuclear higher-twist effects and spin-0 constituents in nuclei are not different from those in nucleons. The European Muon Collaboration effect is reconfirmed, and the low-x data from all recent experiments, at all Q^2, are now in agreement.

Cross sections for 180\ifmmode^\circ\else\textdegree\fi{} inelastic electron scattering from deuterium were measured from breakup threshold to beyond the quasielastic peak for incident-beam energies of 0.843, 1.020, 1.189, and 1.281 GeV, corresponding to $0.75\ensuremath{\le}{Q}^{2}\ensuremath{\le}2.57$ ${(\mathrm{G}\mathrm{e}\mathrm{V}/\mathit{c})}^{2}$. The data are in reasonable agreement with nonrelativistic models that include final-state interactions and meson-exchange currents. The scaling function $F(y)$ for these data is generally in agreement with $F(y)$ for forward-angle data at the same ${Q}^{2}$. Values of ${G}_{M}^{n}$ determined from the data are in good agreement with results from previous experiments.

We report new results on a precision measurement of the ratio R=σL/σT from deuterium, iron and gold targets, on the ratio σFe/σD and on the structure function F2, for deep inelastic electron‐nucleus scattering in the range 0.2≤x≤0.5 and 1≤Q2≤10(GeV/c)2. We find no difference between RFe and Rd. Our results show, for first time, a clear falloff of R with increasing Q2 at SLAC energies. Our R and F2 results are in good agreement with QCD predictions only when corrections for target mass effects are included.

Cross sections for 180° inelastic electron scattering from the deuteron were measured from the break‐up threshold to beyond the quasielastic peak for incident beam energies between 0.7 and 1.3 GeV, corresponding to 0.75≤Q2≤2.75 (GeV/c)2. The data are in reasonable agreement with nonrelativistic models that include final‐state interactions are meson exchange currents.

We report new results on a precision measurement of the ratio R = σ L /σ T from deuterium, iron and gold targets, on the ratio σFe/σ D and on the structure function F 2, for deep inelastic electron-nucleus scattering in the range 0.2 < x < 0.5 and 1 ≤ Q 2 ≤ 10(GeV/c)2. We find no difference between R Fe and R d. Our results show, for first time, a clear falloff of R with increasing Q 2 at SLAC energies. Our R and F 2 results are in good agreement with QCD predictions only when corrections for target mass effects are included.