0000000000230325
AUTHOR
W. Leidemann
Deuteron electrodisintegration near threshold at high momentum transfer
Electrodisintegration of the deuteron near the break-up threshold is a particularly striking example of the existence of exchange currents (EC). While the conventional one-body current contribution grossly underestimates the experimental cross-section up to a momentum transfer of aboutq μ 2 =15 fm−2, the inclusion of EC—dominantly π-MEC—leads to a drastic increase in satisfactory agreement with experimental data up toq 2=9 fm−2.
Tensor and Vector Analyzing Powers in the Reaction 2H(e,e’p)
The first experiment to be performed an the internal target facility of NIKHEF-K will be a study of eleclron-induced quasi-elastic proton knock-out from tensor-polarized deuterium. Here, we present the first results from the experimental tests as well as the results of a Monte Carlo simulation, which show the feasibility of the proposed experiment, even at modest luminosities.
The role of the neutron electric form factor ind(e, e? N)N including polarization observables
The influence of the neutron electric form factor on various observables in two-body break-up of deuterons by electrons such as differential cross section, beam, target and beam-target asymmetries and outgoing nucleon polarization as well is investigated for different kinematic regions. The electron-deuteron vector asymmetryAedV and the outgoing nucleon polarization component P′x(n) are the most promising observables in and off the quasi-free region for a determination ofGEn. Also the single polarization observablesAdT and Py0(p) and the double polarization observable P′z(n) show significant influences fromGEn.
Effective interaction method for hyperspherical harmonics
Abstract The effective interaction hyperspherical harmonics (EIHH) method [1] is outlined. Recent extensions of the approach are discussed. Results for binding energies and radii of various p-shell nuclei are shown.
The role of electromagnetic form factors in meson exchange currents
The question of electromagnetic form factors, i.e. F1V versus GEV, to be used in isovector meson exchange currents in nonrelativistic calculations is critically reviewed. None of the various arguments given earlier in favour of F1V have been found valid. Furthermore, model dependence of theoretical calculations on deuteron threshold disintegration due to e.m. form factor fits and potential models is found to be substantial. In view of these results, relativistic effects have to be included for a clear understanding of this process in the high momentum transfer region.
The relativistic spin-orbit current in deuteron photodisintegration below and above ?-threshold
It is shown that the spin-orbit current which leads to an improved description ofd(γ,p)n below π-threshold is essentially a two-body exchange effect. This is demonstrated by separation of its one-body contribution. Furthermore, above π-threshold its inclusion leads to an improved agreement with experiment, in particular for the differential cross section in the Δ-excitation region.
Polarization Effects in Photo- and Electrodisintegration of the Deuteron
Polarization observables in deuteron photodisintegration like photon and target asymmetries and one- and two nucleon polarization of the final state are studied with respect to their sensitivity to subnuclear degrees of freedom. Furthermore it is shown that the electric form factor of the neutron has a sizeable influence on the polarization asymmetry in d(\(\overset{\lower0.5em\hbox{$\smash{\scriptscriptstyle\rightharpoonup}$}}{e}\),e’n)p with polarized electrons. Uncertainties arising from potential model dependence are discussed.
Proton-neutron correlations and the longitudinal nuclear response
We study the influence of the proton-neutron correlations, in particular of the tensor ones, on the longitudinal nuclear response. They generate a high-energy tail that we evaluate. We show that this tail produces an apparent quenching of the Coulomb sum rule. The amount of quenching found is significant, although insufficient to explain the totality of the missing strength.
Deuteron electrodisintegration near threshold with the Bonn potential
Deuteron electrodisintegration near threshold is calculated for the Bonn potential including consistent meson exchange currents. Experimental data can fairly well be described over the whole q-range if GE is used as electromagnetic form factor for the exchange current, whereas F1 leads to a large overestimation at high q.