I. Sick

DEEP-INELASTIC ELECTRON SCATTERING FROM CARBON

Abstract We have measured the deep-inelastic electron scattering from carbon up to and including the Δ-region at 36°, 60°, 90° and 145°. The systematic decomposition of the transverse and longitudinal response functions has been obtained by means of a Rosenbluth-type analysis of the data in the momentum transfer interval 200 MeV/c /s |q| /s 600 MeV/c. A comparison with theoretical calculations which extend over the quasielastic and Δ-peak regions is presented. A reduction of the differences between our data and theory seems obtainable through the introduction of meson-exchange currents, resonant and non-resonant meson production, and the use of the shell model. Our experimental Coulomb sum-rule estimates at higher | q | agree with independent particle model predictions. We compare our results in the vicinity of the Δ-peak with the total absorption cross section for real photons.

Measurements of the Proton and Deuteron Spin Structure Functions g1 and g2

Measurements are reported of the proton and deuteron spin structure functions g1 at beam energies of 29.1, 16.2, and 9.7 GeV and g2 at a beam energy of 29.1 GeV. The integrals of g1 over x have been evaluated at fixed Q**2 = 3 (GeV/c)**2 using the full data set. The Q**2 dependence of the ratio g1/F1 was studied and found to be small for Q**2>1 (GeV/c)**2. Within experimental precision the g2 data are well-described by the Wandzura-Wilczek twist-2 contribution. 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 for both proton and deuteron targets. A2 for the proton is found to be positive and inconsistent with zero. Measurements of g1 in the resonance region show strong variations with x and Q**2, consistent with resonant amplitudes extracted from unpolarized data. These data allow us to study the Q**2 dependence of the first moments of g1 below the scaling region.

Measurements of the Q**2 dependence of the proton and neutron spin structure functions g(1)**p and g(1)**n

Abstract The ratio g 1 F 1 has been measured over the range 0.03 g 1 F 1 to be consistent with no Q2-dependence at fixed x in the deep-inelastic region Q2 > 1 (GeV/c)2. A trend is observed for g 1 F 1 to decrease at lower Q2. Fits to world data with and without a possible Q2-dependence in g 1 F 1 are in agreement with the Bjorken sum rule, but Δq is substantially less than the quark-parton model expectation.

Deuteron A(Q2) structure function and the neutron electric form factor

We present new measurements of the deuteron A(Q2) structure function in the momentum transfer region between 1 and 18 fm−2. The accuracy of the data ranges from 2 % to 6 %. We investigate the sensitivity of A(Q2) to the nucleon-nucleon interaction and to the neutron electric form factor GEn. Our analysis shows that below 20 fm−2 GEn can be inferred from these data with a significantly improved accuracy. The model dependence of this analysis is discussed.

Spectral function of finite nuclei and scattering of GeV electrons

Abstract We employ the local-density approximation to derive the spectral function P( k , E) of finite nuclei. For various densities of nuclear matter we calculate P( k , E) , and split it into the single-particle and correlated parts. For finite nuclei P( k , E) is calculated by combining the nuclear-matter correlated part, evaluated in local-density approximation, with the finite-nucleus single-particle part obtained from mean-field calculations or (e, e′p) experiments. These spectral functions are used to calculate cross sections for inclusive electron-nucleus scattering at large momentum transfer. The recoil-nucleon final-state interaction is treated in the local-density approximation as well.

Model-independent nuclear charge densities from elastic electron scattering

Abstract We propose a method to extract nuclear charge densities from elastic electron scattering data without using model distributions. Upper limits for the amplitudes of the higher Fourier components of ϱ ( r ), not measured by experiment due to the finite maximum momentum transfer, are derived from theoretical calculations. Among all possibly occupied proton states K the smallest width Γ of the peaks of theoretical radial wave functions R K 2 ( r ) is selected. This width depends little on the type of theoretical calculation used, because it is closely related to the (experimentally known) separation energies. When determining phenomenological charge densities no structures in ϱ ( r ) having a width smaller than Γ are admitted. This constraint permits derivation of charge densities without further model assumptions. Also, realistic error bars on these densities can be obtained. To introduce the condition of a minimal width of structures, and in order to decouple the densities at different radii as much as possible, the phenomenologieal density is written as a sum of many individual components all having this width; a sum of Gaussians (SOG) is used. As an application muonic X-ray data and four sets of (e, e) data on 12 C and 32 S are analysed. The extent to which the charge density can be derived from low, medium or high momentum transfer (e, e) data is discussed. The results are compared to conventional model densities.

Measurements of the Proton and Deuteron Spin Structure Function g2 and Asymmetry A2

We have measured proton and deuteron virtual photon-nucleon asymmetries A2p and A2d and structure functions g2p and g2d over the range 0.03<x<0.8 and 1.3<Q2<10 (GeV/c)2 by inelastically scattering polarized electrons off polarized ammonia targets. Results for A2 are significantly smaller than the positivity limit sqrt(R) for both targets. Within experimental precision, the g2 data are well-described by the twist-2 contribution g2WW. Twist-3 matrix elements have been extracted and are compared to theorectical predictions.

Precise neutron magnetic form factors

Precise data on the neutron magnetic form factor Gmn have been obtained with measurements of the ratio of cross sections of D(e, en) and D(e, ep) up to momentum transfers of Q 2 = 0.9 (GeV/c) 2 . Data with typical uncertainties of 1.5% are presented. These data allow for the first time to extract a precise value of the magnetic radius of the neutron.  2002 Elsevier

Precise measurements of the neutron magnetic form-factor

Abstract The neutron magnetic form factor Gmn has been determined via a measurement of the ratio of cross sections D(e,e′n) and D(e,e′p). The absolute detection efficiency of the neutron detector was measured with high accuracy using tagged neutrons produced from H(n,p)n elastic scattering by means of a high intensity neutron beam. This approach minimizes the model dependence and improves upon the weakest points of previous experiments. Data in the range q2=0.2–0.8 (GeV/c)2 with uncertainties of

Measurement of the deuteron spin structure function g1d(x) for 1 (GeV/c)2 < Q2 < 40 (GeV/c)2

New measurements are reported on the deuteron spin structure function g_1^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<Q^2<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 g_1^d, including Gamma_1^d, and the net quark polarization Delta Sigma.Abstract New measurements are reported on the deuteron spin structure function g1d. These results were obtained from deep inelastic scattering of 48.3 GeV electrons on polarized deuterons in the kinematic range 0.01 6 Li 2 H) as the target material. Extrapolations of the data were performed to obtain moments of g1d, including Γ1d, and the net quark polarization ΔΣ.