A. Lung

A-dependence of nuclear transparency in quasielastic A(e, ef'p) at high Q2

The A-dependence of the quasielastic A(e,ep) reaction has been studied at SLAC with ^2H, C, Fe, and Au nuclei at momentum transfers Q^2 = 1, 3, 5, and 6.8 (GeV/c)2. We extract the nuclear transparency T(A,Q^2), a measure of the average probability that the struck proton escapes from the nucleus A without interaction. Several calculations predict a significant increase in T with momentum transfer, a phenomenon known as Color Transparency. Within the measurement uncertainty, no increase is seen for any of the nuclei studied.

Measurement of the proton elastic form factors for Q2=1−3(Gev/c)2☆

We report measurements of the proton form factors, G^p_E and G^p_M, extracted nfrom elastic electron scattering in the range 1 ≤ Q^2 ≤ 3 (GeV/c)^2 with uncertainties nof <15% in G^p_E and <3% in G^p_M. The results for G^p_E are somewhat larger than nindicated by most theoretical parameterizations. The ratio of Pauli and Dirac form nfactors, Q^2(F^p_2/F^p_1), is lower in value and demonstrates less Q^2 dependence than nthese parameterizations have indicated. Comparisons are made to theoretical models, nincluding those based on perturbative QCD, vector-meson dominance, QCD sum nrules, and diquark constituents to the proton. A global extraction of the form factors, nincluding previous elastic scattering measurements, is also presented.

MEASUREMENTS OF THE NUCLEON FORM FACTORS AT LARGE MOMENTUM TRANSFERS

New measurements of the electric GE(Q2) and magnetic GM(Q2) form factors of the nucleons are reported. The proton data cover the Q2 range from 1.75 to 8.83 (GeV/c)2 and the neutron data from 1.75 to 4.00 (GeV/c)2, more than doubling the range of previous data. Scaled by the dipole fit, GD(Q2), the results forGMp(Q2) /?pGD(Q2) decrease smoothly from 1.05 to 0.92, while GEp(Q2)/GD(Q2)is consistent with unity. The preliminary results for GMn(Q2) /?nGD(Q2) are consistent with unity, while GEn is consistent with zero at all values of Q2.

Precision measurement of R=σL/σT and F2 in deep inelastic electron scattering

Abstract 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.

Measurement of R = σL/σT and F2 on Deuterium and Iron in Deep Inelastic Electron Scattering

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.

A study of the nuclear and kinematic dependence of R = σL/σT in deep inelastic electron scattering☆

Abstract We report preliminary results on the nuclear dependence of R = σL/σT in the deep inelastic electron scattering from deuterium, iron, and gold nuclei. In the x, Q2 range of 0.2 ⩽ x ⩽ 0.5 and 1 ⩽ Q2 ⩽ 5 (GeV/c)2, the average RFe − RD is 0.03 ± 0.02 (stat) ± 0.06 (syst); the final systematic errors are expected to be reduced to ± 0.03. The results indicate that there are no significant spin-0 constituents or higher twist effects in nuclei as compared to free nucleons. Models for the EMC effect with significant nuclear dependence of R are ruled out. The discrepancy, at low x, between CERN and SLAC results for the cross section ratio σFe/σD cannot be attributed to a nuclear dependence of R as suggested by some authors. The kinematic variation of RD with x and Q2 in the SLAC energy is in agreement with the predictions of QCD with the addition of target mass effects.

Precision measurement of R=σL/σT and F2 in deep inelastic electron scattering on deuterium and iron targets

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.

Transverse inelastic electron scattering from the deuteron at high momentum transfers

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.