Nuclear Phys. A 634 (1998) 463
The nuclear electric polarizability is theoretically analyzed using a sum rule derived from the longitudinal part of the forward Compton amplitude. Beyond the leading dipole contribution, this approach leads to the presence of potential-dependent terms that do not show up in previous analyses. The significance of these new contributions is illustrated by performing an explicit calculation for a proton-neutron system interacting via a separable potential.
Phys. Rev. C 58 (1998) 582
The spectral function of 4He is calculated with the Lorentz integral transform method in a large energy and momentum range. The excitation spectrum of the residual 3N-system is fully taken into account. The obtained spectral function is used to calculate the quasi elastic longitudinal (e,e') response RL of 4He for q = 300, 400, and 500 MeV/c. The consistent comparison with the exact RL shows that the disagreement is rather sizeable at high energies and reduces to about 10% in the quasi elastic peak at q=500 MeV/c. The description of RL by means of the spectral function is rather poor at lower energies.
Phys. Rev. Lett. 78 (1997) 432
The longitudinal (e,e') response function of 4He is calculated precisely with full final state interaction. The explicit calculation of the four-body continuum states is avoided by the method of integral transforms. Precision tests of the response show the high level of accuracy. Non--relativistic nuclear dynamics are used. The agreement with experimental data is very good over a large energy range for all considered momentum transfers (q=300, 400, 500 MeV/c). Only at higher q the theoretical response overestimates the experimental one beyond the quasi-elastic peak.
Phys. Rev. Lett. 78 (1997), 4015
A four-nucleon calculation of the total 4He photodisintegration
cross section is performed. The full final-state interaction is taken into
account for the first time. This is achieved via the method of the Lorentz
integral transform. Semi-realistic NN interactions are employed. Different
from the known partial two-body 4He(g,n)3He and 4He(g,p)3H
cross sections our total cross section exhibits a pronounced giant resonance.
Thus, in contrast to older (g ,np) data, we predict quite a strong contribution
of the (g ,np) channel at the giant resonance peak energy.
Phys. Lett. B 408 (1997) 1
The total photodisintegration cross sections of three--body nuclei are calculated with semirealistic NN potentials below pion threshold. Full final state interaction with Coulomb force is taken into account via the Lorentz integral transform method. The experimental total cross sections are well described and the sum rule sigma-1(3H) agrees with elastic electron scattering data. The calculated 3He polarizability is 0.15 fm3.
Phys. Rev. Lett. 78 (1997) 4011
The differential cross section and the trsnsverse interference structure fun cion for the reaction 2H(e,e') haaver been determined at an np invariant mass of 2.16 GeV. The data, covering a 40°ree; range in the proton emission angle, indicate that delta excitation ang subsequent Ndelta interaction is the dominant reaction mechanism. Calculations performed within an N-delta coupled-channel approach reproduce the cross section data, but understimate the fTT by 30 or 40 percent.
Phys. Rev. C 54 (1996) 1766
The28Si(g pol,np)Xreaction has been studied using the Ladon polarized and tagger gamma-ray beam, in the energy region between 50 and 78 MeV. The data have been compared with the quasideuteron mechanism. At the highest photon energy the applied model leads to a satisfactory description of both the unpolarized cross section and beam polarization asymetry.
Phys. Rev. C 53 (1996) 1506
The symmetry of diprotons leads to dramatic features in the 2He(gamma,pp) beam polaritazion asymmetry that are very different from those of deuteron photodisintegration. Calculations using realistic Faddeev wave functions show that striking features schould persist for 1S0 p-p pairs embedded in 3He, and these challenge the simple interpretarion given to recent 3He (gamma,pp)n measurements.
Phys. Lett. B 366 (1996) 354
Making use of QCD sum rules a lower bound to the value of the electromagnetic polarizability alphaE of charged pions is given. We find that, if present constraints on the duality threashold are accepted, this lower bound is incompatible with the value predicted by chiral perturbation theory, as well as with the lowest experimental result.
V.D.Efros, W. Leidemann, G.Orlandini and E.L.Tomusiak
The inclusive reactions g+3H ®X and e+ 4H e® e’+X are studied with the Lorentz integral transform method. The method allows the inclusion of the full final-state interaction without explicit knowledge of the continuum states. Features of the inversion procedure are discussed in this work. The technique for the calculation of the matrix elements of the Hamiltonian is described. The total photoabsorption cross section of 3H is calculated with a realistic super-soft-core NN force. In the threshold region the cross section is rather similar to that obtained with central forces only, while in the peak the realistic NN interaction leads to more strength. For the longitudinal (e,e’) response we extend our calculation with a semirealistic force to q= 600 MeV/c. Rather good agreement with experimental data is found. The accuracy of the quasielastic response approximation is discussed.
Fizika B, 8 (1999) 181
The general formulation of a technically advantageous method to
find the. ground state solution of: the Schrödinger equation in configuration
space for systems with the number of particles A greater than 4 is presented
The wave function is expanded in pair-correlated hyperspherical harmonics
beyond the lowest-order approximation and then calcu1ated in the Faddeev
approach. A recent efficient, recursive method to construct antisymmetric
A-particle hyperspherical harmonics is used. The accuracy is tested for
the bound-state energies of nuclei with A = 6 to 12 using the effective
V4 potentials. The high quality of the results thus obtained becomes
evident from a comparison with other approaches.
Few Body Sys. 26 (1999) 251
The Lorentz integral transform method is described briefly. The resulting differential equations are solved via an expansion in hypersherical harmonics, and a new approach is introduced for incorporating correlations in the basis functions. New results for the tota1 photoabsorption cross section of 3H and 3He are presented. It is shown that the peak of the cross section is strongly affected by the three-nucleon force. In addition, we review the results for the 4He electromagnetic response functions obtained with the Lorentz integral transform method.
Phys. Rev. Lett. 82 (1999) 687
We report on a first measurement of tensor analyzing powers in quasielastic electro-deuteron scattering at an average three-momentum transfer of 1.7fm-1. Data sensitive to the spin-dependent nucleon density in the deuteron were obtained for missing momenta up to 150 MeV/cwith a tensor polarized 2H target internal to an electron storage ring. The data are well described by a calculation that includes the effects of final-state interaction, meson-exchange and isobar currents, and leading-order relativistic contributions.
