The proton elastic form factors GEp(Q2) and GMp(Q2) have been extracted for Q2=1.75 to 8.83 (GeV/c)2 via a Rosenbluth separation to ep elastic cross section measurements in the angular range 13°≤θ≤90°. The Q2 range covered more than doubles that of the existing data. For Q2<4 (GeV/c)2, where the data overlap with previous measurements, the total uncertainties have been reduced to < 14% in GEp and < 1.5% in GMp. Results for GEp(Q2) are consistent with the dipole fit GD(Q2)=(1+Q2/0.71)−2, while those for GMp(Q2)/μpGD(Q2) decrease smoothly from 1.05 to 0.92. Deviations from form factor scaling are observed up to 20%. The ratio Q2F2/F1 is observed to approach a constant value for Q2>3 (GeV/c)2. Comparisons are made to vector meson dominance, dimensional scaling, QCD sum rule, diquark, and constituent quark models, none of which fully characterize all the new data.
Axis error includes +- 1.6/1.6 contribution (Point-to-point systematic error. The quadrature sum of the point-to-point uncertainties in all quantities which defined the cross section).
Axis error includes +- 1.6/1.6 contribution (Point-to-point systematic error. The quadrature sum of the point-to-point uncertainties in all quantities which defined the cross section).
Axis error includes +- 1.6/1.6 contribution (Point-to-point systematic error. The quadrature sum of the point-to-point uncertainties in all quantities which defined the cross section).
We have performed absolute measurements of the differential cross section for elastic e−p scattering in the range of momentum transfer from Q2=2.9 to 31.3 (GeV/c)2. Combined statistical and systematic uncertainties in the cross-section measurements ranged from 3% at low Q2 to 19% at high Q2. These data have been used to extract the proton magnetic form factor GMp(Q2). The results show a smooth decrease of Q4GMp with momentum transfer above Q2=10 (GeV/c)2. These results are compared with recent predictions of perturbative QCD.
No description provided.
No description provided.
No description provided.
Quasielastic e-d cross sections have been measured at forward and backward angles. Rosenbluth separations were done to obtain RL and RT at Q2=1.75, 2.50, 3.25, and 4.00 (GeV/c)2. The neutron form factors GEn and GMn 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 GMn are consistent with the dipole form, while GEn 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.
Magnetic form factors.
Electric form factors.
Cross sections for deep-inelastic electron scattering from liquid deuterium, gaseous He4, and solid Be, C, Al, Ca, Fe, Ag, and Au targets were measured at the Stanford Linear Accelerator Center using electrons with energies ranging from 8 to 24.5 GeV. These data cover a range in the Bjorken variable x from 0.089 to 0.8, and in momentum transfer Q2 from 2 to 15 (GeV/c)2. The ratios of cross sections per nucleon (σAσd)is for isoscalar nuclei have been extracted from the data. These ratios are greater than unity in the range 0.1<x<0.3, while for 0.3<x<0.8 they are less than unity and decrease logarithmically with atomic weight A, or linearly with average nuclear density. No Q2 dependence in the ratios was observed over the kinematic range of the data. These results are compared to various theoretical predictions.
Additional overall systematic error of 2.1 pct plus a target to target systematic error of 1 pct.
Additional overall systematic error of 2.1 pct plus a target to target systematic error of 2.1 pct.
Additional overall systematic error of 2.1 pct plus a target to target systematic error of 0.6 pct.
The proton elastic electric and magnetic form factors, GEp(Q2) and GMp(Q2), have been separately measured in the range Q2=1.75 to 8.83 (GeV/c)2, more than doubling the Q2 range of previous data. Scaled by the dipole fit, GD(Q2), the results for GMp(Q2)/μpGD(Q2) decrease smoothly from 1.05 to 0.91, while GEp(Q2)/GD(Q2) is consistent with unity. Comparisons are made to QCD sum rule, diquark, constitutent quark, and vector meson dominance models, none of which agree with all of the new data. The ratio Q2F2/F1 approaches a constant value for Q2>3 (GeV/c)2.
Magnetic form factors.
Electric form factors.
Measurements of the forward-angle differential cross section for elastic electron-proton scattering were made in the range of momentum transfer from Q2=2.9 to 31.3 (GeV/c)2 using an electron beam at the Stanford Linear Accelerator Center. The data span six orders of magnitude in cross section. Combinded statistical and systematic uncertainties in the cross section measurements ranged from 3.6% at low Q2 to 19% at high Q2. These data have been used to extract the proton magnetic form factor GMp(Q2) and Dirac form factor F1p(Q2) by using form factor scaling. The logarithmic falloff of Q4F1p expected from leading twist predictions of perturbative quantum chromodynamics is consistent with the new data at high Q2. Some nonperturbative and hybrid calculations also agree with our results.
No description provided.
Formfactor scaling assumes (Ge=Gm/mu).
The spin structure function of the neutron g1n has been determined over the range 0.03<x<0.6 at an average Q2 of 2 (GeV/c)2 by measuring the asymmetry in deep inelastic scattering of polarized electrons from a polarized He3 target at energies between 19 and 26 GeV. The integral of the neutron spin structure function is found to be F01g1n(x)dx=-0.022±0.011. Earlier reported proton results together with the Bjorken sum rule predict F01g1n(x)dx=-0.059±0.019.
No description provided.
Extrapolarity to full x range.
We report measurements of the proton elastic form factors, G E p and G M p , extracted from electron scattering in the range 1⩽ Q 2 ⩽3(GeV/ c ) 2 . The uncertainties are <15% in G E p and <3% in G M p . The values of G E p are larger than indicated by most theoretical parameterizations, The ratio of Pauli and Dirac form factors, Q 2 F 2 p / F 1 p , is lower and demonstrates less Q 2 dependence than most of these parameterizations. Comparisons are made to theoretical models, including those based on perturbative QCD and vector-meson dominance.
No description provided.
No description provided.
No description provided.
We studied the electroproduction of the Delta(1232) resonance via the reaction p(e,e'p)\pi0 at four-momentum transfers Qsq = 2.8 and 4.0 GeV^2. This is the highest Qsq for which exclusive resonance electroproduction has ever been observed. Decay angular distributions for Delta to p-pi0$ were measured over a wide range of barycentric energies covering the resonance. The $N-\Delta$ transition form factor G*_M and ratios of resonant multipoles E{1+}/M{1+} and S{1+}/M{1+} were extracted from the decay angular distributions. These ratios remain small, indicating that perturbative QCD is not applicable for this reaction at these momentum transfers.
CONST(NAME=E1+/M1+) and CONST(NAME=S1+/M1+) are the ratios of the electric quadrupole moment to magnetic dipole moment and Coulomb quadrupole moment to magnetic dipole moment, respectively (see paper). Resonance only.
CONST(NAME=E1+/M1+) and CONST(NAME=S1+/M1+) are the ratios of the electric quadrupole moment to magnetic dipole moment and Coulomb quadrupole moment to magnetic dipole moment, respectively (see paper). Resonance only.
CONST(NAME=E1+/M1+) and CONST(NAME=S1+/M1+) are the ratios of the electric quadrupole moment to magnetic dipole moment and Coulomb quadrupole moment to ma gnetic dipole moment, respectively (see paper). Resonance + background.
We report measurements of the proton form factors GEp and GMp extracted from elastic scattering in the range 1≤Q2≤3 (GeV/c)2 with total uncertainties < 15% in GEp and < 3% in GMp. 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 GEp are somewhat larger than indicated by most theoretical parametrizations, and the ratios of the Pauli and Dirac form factors Q2(F2pF1p) are lower in value and demonstrate a weaker Q2 dependence than those predictions. A global extraction of the elastic form factors from several experiments in the range 0.1 0.1<Q2<10 (GeV/c)2 is also presented.
Point-to-point systematic uncertainty is 0.5%, overall normailzation uncertainty is 1.9%.
Point-to-point systematic uncertainty is 0.5%, overall normailzation uncertainty is 1.9%.
Point-to-point systematic uncertainty is 0.5%, overall normailzation uncertainty is 1.9%.
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