Search

Nuclear effects in polarized inelastic electron scattering off polarized $^3He$ are discussed; in the kinematics of future experiments at CEBAF, Fermi motion effects are found to be much larger than in deep inelastic scattering. It is shown that improperly describing nuclear dynamics would lead to the extraction of unreliable neutron spin structure functions. On the other hand side, a simple and workable equation relating the Gerasimov -- Drell -- Hearn Integral for the neutron to the corresponding quantity for $^3He$ is proposed.

Effects of the nuclear medium on the transverse response function of inclusive inelastic electron scattering are studied and shown to be substantial at high momentum transfer. In a relativistic Fermi gas model the recently published SLAC data for 56Fe at |q| = 1.14 GeV/c can be reasonably well described if one takes the one-body and two-body meson exchange currents into account together with medium-modified nucleon and Δ masses.

Inelastic electron scattering with energy transfers in the region of the Δ(3, 3) resonance is described by the excitation of nuclear Δ A ∗ resonances. Compared to the quasifree Δ excitation picture we observe an increase of the excitation strength at energies below the quasifree resonance peak as is indicated by recent experimental results from Saclay. This contribution reflects the ΔN-dynamics in the nuclear medium. We conclude that the deep inelastic (e, e′) reaction offers a convenient tool to study the internal N∗ excitations of bound nucleons and thus complements the information obtained from pion induced reactions.

Response functions for inelastic electron scattering from 58 Ni have been determined for momentum transfers of q ≈ 0.4–2 fm −1 . A multipole decomposition of the full continuum for excitation energies below 35 MeV yields new features of the E1 and E3 strengths. The E2 strength is in excellent agreement with α-scattering data which demonstrates the usefulness of both probes and shows the isospin purity of the isoscalar giant quadrupole resonance.

The recently formulated theory of the impulse approximation in QCD is developed further. The integro-differential equation describing the evolution of the parton's distribution function is solved. The formalism is applied to compute R = σL/σT in deep inelastic electron scattering and the average transverse momentum 〈kT〉 of the Drell-Yan pairs. The cross section formula for the latter process is significantly different from the one recently conjectured. Agreement with recent data is good in both cases.

The low-lying quadrupole states in 142 Nd were investigated by inelastic electron scattering. The momentum transfer range covered was 0.5–2.8 fm − . The extracted transition charge densities indicate quite different characters for these states. On the basis of a quasiparticle-phonon nuclear model calculation this difference can be understood as arising from an interplay between collective and single-particle aspects.

Cross sections for inclusive inelastic electron scattering from H, D, Be, Al, Cu and Au have been measured at 6° for incident energies up to 19.5 GeV. Within the stated errors, the cross sections were found to be directly proportional to the sum of the constituent nucleon cross sections.

The effect of nuclear binding and Fermi motion on the ratio R A = σ L σ T is estimated using a convolution model appropriate at finite Q2 values and x≳0.2. The difference in RA compared to the free nucleon ratio RN is predicted to be negligible within experimental error bars. The Q2 dependence of the EMC effect is also investigated.

The excitation of 0+ states in 58Ni and 26Mg has been investigated by inelastic electron scattering. Shell model calculations in a 1&ℏ;ω model space are not able to reproduce the data, which clearly show contributions from 2&ℏ;ω, i.e. giant monopole resonance-like, excitations.

The search for magnetic dipole transitions from the ground state-even Ca isotopes to high lying Jπ=1+ states by means of low momentum transfer but high resolution inelastic electron scattering is described. The previously detected strongly excited Jπ=1+ state EX=10.319 MeV [B(M1)↑=1.12±0.27μK2] in 40Ca has been confirmed, but - contrary to the expectations of the independent particle shell model - only a fairly weak M1 transition is observed in 42 Ca [E X = 11.235 MeV , B( M 1)↑=0.59±0.05 μ 2 K ] and none in 44Ca between EX=8.2−12.2 MeV. In 48Ca, however, a very strong M1 transition [B(M1) ↑ = 4.0 ± 0.3 μ2K] to a single state at EX=10.227 MeV has been discovered.

High-resolution (e,e′) was used to measure the form factor of the 6−, T=1 resonance in 28Si. The results disagree with previous experimental results and with theoretical calculations. The role of meson-exchange currents in producing the observed quenching of magnetic strength, and the relevance of (e,e′) to other reactions are briefly discussed.

We have measured inclusive electron scattering cross sections on 3 He at incident energies up to 667 MeV. The transverse and longitudinal response functions were extracted at four-momentum transfers between −0.1 (GeV/ c ) 2 and −0.3 (GeV/ c ) 2 and up to an energy transfer of 450 MeV. The data are compared to recent theoretical calculations which include many-body effects.

Inelastic electron scattering cross sections, measured for 14 C J π = 4 − states at 11.7, 17.3, and 24.3 MeV, have been combined with previously measured (π, π') cross-section ratios to deduce the isoscalar and isovector amplitudes of the spin transition densities. The T = 1 states exhaust (33–45)% of the isovector single-particle strenght, and (1–15)% of the isoscalar strength. Pion scattering cross sections for the T = 2, 4 − state 24.3 MeV are predicted.

Inelastic electron scattering with high energy resolution (FWHM = 30 keV) has been used to study the states at 6.05(0 + ), 6.13(3 − )and 6.92(2 + ) MeV excitation energy in 16 O for momentum transfers q =0.22–0.49 fm −1 . The experiment yields a new determination of reduced transition probabilities and radiative widths for ground-state transitions.

High-resolution inelastic electron scattering (FWHM ≈ 33 keV) with 50 MeV and 63.5 MeV electrons on 208 Pb has been used to study magnetic excitations between E x =6 MeV and 8 MeV. Angular distributions were analyzed in terms of the DWBA with RPA wave functions. Eight J π =2 − states carrying a total strength ∑ B (M2)↑=8500 ω 2 K fm 2 have been found. The strong fragmentation is in qualitative agreement with theoretical predictions.

The total form factor square of orbital M1 excitations in 164 Dy has been determined up to momentum transfer values q eff =1.6 fm −1 using high-resolution inelastic electron scattering. The total orbital M1 strength in 164 Dy of ΣB (MI)↑=5.17±0.52 μ 2 N is the largest M1 strength observed in a heavy deformed nucleus. It is clustered in two groups of levels, the strongest centered around E x ∽3.1 MeV , the other around 2.6 MeV.

It is shown that the unusual shape of the Coulomb form factor for the 0 gnd + → 4 1 + transition in 56 Fe can be attributed to the enhance collectivity due to the strong correlation between protons and neutrons in the shell-model wave functions.

The momentum transfer dependence ( q =0.20−0.59 fm −1 ) of the recently discovered M1 transition from the J π =1 + state at E x =5.846 MeV to the ground state of 208 Pb has been studied with high-resolution inelastic electron scattering. The experimental data are compared to results of RPA calculations which include tensor correlations. The influence of these correlations and of the interference of proton and neutron contributions on the M1 transition will be discussed.

A new schematic model including the continuum is proposed to analyze momentum-transfer dependences of the escape widths of giant multipole resonances observed by inelastic electron scattering.

The location of the M2 giant resonance in 28Si, 90Zr and 208Pb, predicted within the framework of the MSI-RPA particle- hole model, has been confirmed by high-resolution inelastic electron scattering ( E X ≈ 44A − 1 3 MeV ). The fragmented M2 strength distribution can only be described assuming a mass-dependent quenching of the intrinsic gs factor. This has the consequence that the long sought M1 strength is much reduced in heavy nuclei, an effect which is supported experimentally.

Following the recent discovery of a very strong magnetic dipole transition in 48 Ca to a state at 10.23 MeV in high-resolution inelastic electron scattering, results of a detailed search for M1 strength in the other N = 28 Isotones 50 Ti, 52 Cr and 54 Fe are described. The M1 strength found in the investigated region of excitation energy E x ≈ 7–12 MeV is very fragmented and considerably quenched in comparison to predictions of shell model calculations in a model space that includes up to 2p-2h excitations.

A recently observed Kπ = 1+ mode in deformed nuclei is studied microscopically. By calculating the energies, the B(M1)-values and the form-factors of inelastic electron scattering for 156Gd, we conclude that the relatively strong M1-strength observed at 3.075 MeV comes predominantly from the convection current of proton excitations in the Oh 1 2 - orbit . We suggest a search for the M1-strength around 4 MeV, which arises from proton excitations in deformation-aligned orbits.

The E2 form factors for the first three Jπ=2+ levels in 56Fe, measured in (e, e′) reactions for momentum transfers qeff

The discovery of a new collective magnetic dipole excitation mode in high-resolution inelastic electron scattering on 64 156 Gd is discussed in terms of a geometrical two-rotor model and the interacting boson model. Besides in the deformed nucleus 156 Gd evidence has also been accumulated for the existence of this mode in 158 Gd and for the absence in the transitional nucleus 60 146 Nd in agreement with the theoretical prediction.

Inelastic electron scattering experiments were performed on a 17 O gas target in a range of momentum transfer q = 0.6−1.1fm −1 ; B (E3) values for twelve odd-parity levels were obtained from the measured Coulomb form factors. The results are discussed in terms of the weak coupling model.

The European Muon Collaboration (EMC) effect in 12C, 40Ca and 56Fe is calculated taking nucleon binding and correlations resulting from realistic many-body calculations properly into account. The effect of Q2-rescaling is also investigated.

High-resolution inelastic electron scattering on 154 Sm, 158 Gd, 164 Dy, 168 Er and 174 Yb provides further evidence on the recently discovered low-lying magnetic dipole mode. We present here spectra, form factors and estimates for transition strengths and use mainly the interacting boson model (IBA-2) for comparison. We also show first results on the fragmentation of the strength of the new mode in 156 Gd.

A second-order perturbative calculation is reported for core-polarization effects on the matrix elements 〈 p −1 3 2 d 5 2 ; T, J π =4 − | M 4| 16 O core ; 0 + 〉 with T =0 and T =1 or the stretched-magnetic (M4) excitation in 16 O. It is found that the matrix elements are reduced from the single-particle value by both first- and second-order correction terms with comparable magnitudes, and the reductions come mainly from the central part of the nucleon-nucleon interaction. The reduction of the strength observed in inelastic electron scattering experiments is well explained by the core polarization. The calculated results are quite consistent for two different sets of realistic interactions, the Paris potential and the Reid soft-core potential.

We explore a method for combined analysis of inelastic electron-scattering data and muonic quadrupole hyperfine-splitting measurements. The method, applied here to 152 Sm, provides an accurate normalization for (e, e′) data, a precise value for B (E2; 0 + → 2 + ), and shows that the interpretation of the monopole (elastic) and quadrupole (inelastic) data from both experiments is consistent at the present level of experimental accuracy.

It is shown that in the relativistic many-body theory the Coulomb sum rule value is never exhausted in the space-like momentum transfer region. This implies that the Coulomb sum rule should be used with a particular caution to analyze deep inelastic electron scattering from nuclei.

A fluctuation analysis technique and the comparison of experimentally deduced strength distributions with a statistical one have been used to extract level densities as a function of excitation energy from high-resolution inelastic electron scattering spectra. Both methods yield for the Jπ = 2− states around E x = 9 MeV in 90 Zr mean level spacings 〈D〉 = 6.5±1.6 keV and 〈D〉 = 5.5 ± 1.5 keV, respectively. Those level densities are then employed to estimate the magnetic quadrupole strength that is hidden in the background and escaped direct experimental detection.

The rising σ( v )/σ(v) ratio is quantitavely predicted from deep inelastic electron scattering, in particular from the scaling violations observed for the difference of the proton and neutron structure functions. The parametrization of the deviations from scaling is based on a simple two-component picture of deep inelastic scattering.

I estimate the contributions of meson exchange currents and final state interactions to the longitudinal and transverse response functions of 3 He. They improve their usual one-body descriptions.

The differential cross section of inelastic electron scattering for the low-lying “collective” Kπ=1+ excitations in rare-earth nuclei is calculated in DWBA by using microscopically calculated transition-densities. In the region of low-momentum transfer (q⪅0.5 fm-1) in which experimental data are available the shape of calcualted cross sections is almost the same for all nuclei and is slightly but systematically different from the observed shape.

We study the effects of core configuration mixing on inelastic electron scattering for the first 2 + and 3 − levels of single closed-shell nuclei such as 92 Mo and 52 Cr. The theory accounts fairly well for the octupole states where particle hole core polarization is important. This last effect is weak for the quadrupole states and our description fails totally to account for their collectivity.

The distributions of the allowed muon capture strengths in 1p-shell nuclei are shown to exhibit a tendency to concentrate in a few low-lying daughter states. These strong excitations are analogs of the giant magnetic dipole transitions, predicted by Kurath, and observed in inelastic electron scattering. Similar excitations are expected in 1S radiative pion capture and low-energy charged pion photoproduction processes.

We have considered the influence of short-range dynamical and statistical correlations on the inelastic scattering of electrons from light nuclei. The correlation effects are discussed on the example of the longitudinal sum rule for the 16O and 12C nuclei. A remarkable increase in the sum rule, caused by the short-range correlations at medium momentum transfers (100–200 MeV), is pointed out.

The corrections to vector meson dominance relating high energy Compton scattering and ϱ-photo-production at t = 0 are estimated using the operator expansion near the light cone and the experimental results on deep inelastic electron scattering.

Elastic and inelastic electron scattering form factors for the ground (01+ and first 2+ and 4+ states are calculated in the unrestricted, projected, Hartree-Fock approximation and compared with experimental data. A practical method, applicable to any type of wavefunction, is given for the calculation of the center-of-mass correction, to the form factor.

Using soft pion method, it is shown that the structure function F L e π→ e+anything (ω) m π 2 =0 =0 . With the aid of factorization of single Regge exchange, it follows that F L eN→e+anything ( ω ) = 0 for ω where Pomeron contribu tion dominates.

The multipole expansion of the inelastic electron scattering continuum in 90Zr yields an E2-like structure which involves a giant monopole resonance at 17 MeV with a width of 4 MeV.

The total cross-section for production of hadrons by inelastic electron scattering at 3.2° from hydrogen and deuterium has been measured in the Q 2 range 0.015 GeV 2 to 0.1 GeV 2 , at virtual photon energies ranging from 2 GeV to 8.5 GeV. The transition to photoproduction is observed to be smooth, the ratio σ D /σ H being about 1.85 in this range. No evidence is seen for a conjectured rapid Q 2 -dependence of this ratio at low Q 2 .

The electron scattering form factor for the excitation of the 0 2 + state for 4 He is calculated in the symplectic shell model and the results are compared with experiment.

The configuration of the 6.0 MeV 4+ state in 24Mg has been investigated using the inelastic electron scattering form factor for this level. It is shown that 1s-0d shell cannot describe the observed form factor succesfully. The amount of 0g shell admixture in this transition is estimated. Saxon-Woods wavefunctions and phase-shift analysis have been used.

Low-energy inelastic electron scattering experiments have been performed for 208 Pb with excitation energy ranging from 5 to 22 MeV. Resonances are observed at 7.3, 7.9, 8.9, 10.2, 10.6, 11.2 and 14.1 MeV. For the triple at 10.2, 10.6 and 11.2 MeV, evidence is presented for an E2 assignment, with a reduced transition probability B (E2,0) = (2.6 ± 0.9) × 10 3 fm 4 .

The form factors for inelastic electron scattering to the first excited 0 + levels in 16 O and 40 Ca are calculated using the Brown and Green model. It is shown that the form factors are strongly dependent on the deformations of the states. The monopole matrix element of the 40 Ca 0 + → 0 + transitions becomes 2.46 fm 2 (exp. 2.5 fm 2 ).

Inelastic electron scattering from factors have been measured and B (E2) values extracted for the first four excited states of 51 V. The B (E2) values agree with a shell-model description of the states for an effective proton charge of 1.6 e .