Nuclear mass form factors from coherent photoproduction of πmesons

Data for coherent photoproduction of π⁰ mesons from nuclei ( ¹²C, ⁴⁰Ca, ⁹³Nb, ^natPb), recently measured with the TAPS detector at the Mainz MAMI accelerator, have been analyzed in view of the mass form factors of the nuclei. The form factors have been extracted in plane-wave approximation of the A(γ,π⁰)A reaction and corrected for final-state interaction effects with the help of distorted-wave impulse approximations. Nuclear mass rms radii have been calculated from the slope of the form factors for q² → 0. Furthermore, the Helm model (hard-sphere form factor folded with Gaussian) was used to extract diffraction radii from the zeroes of the form factor and skin thicknesses from the position and height of its first maximum. The diffraction radii from the Helm model agree with the corresponding charge radii obtained from electron scattering experiments within their uncertainties of a few per cent. The rms radii from the slope of the form factors are systematically lower by up to 5% for PWIA and up to 10% for DWIA. Also the skin thicknesses extracted from the Helm model are systematically smaller than their charge counterparts.     

Elastic scattering of intermediate energy protons on4He and12C

The elastic angular distribution and polarization of ～1 GeV protons on⁴He and¹²C have been analysed using the recently proposed correlation expansion for the Glauber amplitude by retaining terms up to three-body density only. The calculations include Coulomb and spin effects. Using realistic form factors for target nuclei it is found that we need to consider only up to the second-order density term to provide a satisfactory explanation of both kinds of experimental data in the available momentum transfer region. The contribution of the three-body density term is only marginal except in⁴He differential cross-section in the cm angular range 45°<θ _cm<65°.     

Proton spectroscopic factors of Sm isotopes in the pairing-plus-quadrupole model

Proton spectroscopic factors have been calculated for the single-proton states in Sm isotopes with N = 84–92 by using the deformed quasiparticle wave functions obtained in the pairing-plus- quadrupole model. Comparison is given with the experimental data from the pick-up reactions (d, ³He) and (t, ⁴He) to the product nuclei ^145–153Pm. Effects of deformation on the spectroscopic factors are studied.     

Finite-range DWBA analyses of (dt) and (d3He) reactions on 64Zn at Ed = 13 MeV

Exact finite-range DWBA analyses of ($\text{d}\text{, t}\text{)}$ and $\text{(}\text{d}\text{d}$, ³He) reactions have been performed for an ⁶⁴Zr target at an incident deuteron energy of 13.0 MeV, leading to the ground states of the residual nuclei. The microscopic overlap functions for (d, t) and (d, ³He) systems obtained by using the Phillips triton wavefunctions have been used as projectile form factors into the calculation. The results are compared with zero-range DWBA calculations taking the finite-range effects into account by means of a local energy approximation. The results obtained by finite-range and zero-range calculations for differential cross sections as well as vector and tensor analysing powers are compared with the experimental data. The range of validity of the local energy approximation is discussed.     

Spectroscopic Measurement in 9He and 12Be

Spectroscopy for neutron-rich nuclei ⁹He and ¹²Be has been performed by means of heavy-ion double charge exchange (HIDCX) (¹⁸O, ¹⁸Ne) reaction on stable target nuclei ⁹Be and ¹²C, respectively. Several clear peaks in ¹²Be at low excitation energy region even above neutron separation energy have been observed in one-shot measurement, whereas no prominent signals of ⁹He have been observed owing to the small cross section. It is shown that the HIDCX reaction is a new powerful spectroscopic tool for study of unstable neutron-rich nuclei.     

Nucleon momentum distributions in doubly closed shell nuclei

The momentum distributions in nuclei like⁴He,¹⁶O and⁴⁰Ca are explicitly calculated within a phenomenological model which includes dynamical short range and tensor correlation effects. The common behaviour of such distributions in the high momentum region, already established in light nuclei, is extended to the medium weight region. Comparison with existing calculations is discussed and, for completeness, also form factors are evaluated within the same framework.     

Electron charge form factors and static properties of extremely light 1p-shell nuclei within the anisotropic-oscillator model involving projections

The mirror odd nuclei ⁷Li and ⁷Be and the neutron-rich nucleus ⁶He are considered within a microscopic approach relying on the variational principle. The binding energies of the nuclei, their root-mean-square radii, and the electron charge C0 and C2 form factors are calculated. The resulting form factors are compared with the predictions of the independent-particle model that assumes intermediate coupling. The sensitivity of the nuclear properties obtained here to the choice of nucleon-nucleon potential, to deviations of the nuclear deformation from that which follows from a variation of the total-energy functionals, and to taking projections onto states characterized by definite values of the total angular momentum and its projection is analyzed. A comparison with experimental data is performed.     

Three-nucleon interaction in 3-, 4- and ∞-body systems

We report results of variational calculations of ³H, ³He, ⁴He and nuclear matter with the Urbana v₁₄ two-nucleon interaction and realistic models of the three-nucleon interaction (TNI). These include the Tucson and isobar intermediate-state models of the two-pion exchange TNI. The latter is also studied with an intermediate-range three-nucleon repulsion. In general, realistic TNI helps to bring the theory closer to experiment by giving extra binding energy to the A = 3 and 4 nuclei and providing extra saturation to the nuclear matter binding energy. The Coulomb energy of ³He and the rms radii of A = 3, 4 nuclei are also well described. However, some problems remain unresolved. There is a slight overbinding of ⁴He, an underbinding of nuclear matter, and the charge form factors of ³He and ⁴He, calculated with impulse approximation, deviate from the experimental at q²>5 fm^?2.     

Detailed study of the cluster structure of light nuclei in a three-body model: (II). The spectrum of low-lying states of nuclei with A = 6

The three-body α + 2N model developed in our earlier works to describe the ground states of the A = 6 nuclei is generalized here to describe the spectrum of the low-lying states of these nuclei. The levels of the nuclei are shown to be differently sensitive to the various Nα interaction components, whence some conclusions concerning the true form of the Nα interaction are drawn. The geometric structure of the ⁶Li and ⁶He ground states is studied in detail. A significant contribution of the stretched cigar-shaped three-particle configuration NαN with an α-particle between two nucleons has been found. The wave functions of the ground and excited states of the A = 6 nuclei are tabulated. The wave functions found have been tested carefully using numerous experimental data.     

Nucleon momentum distributions and elastic electron scattering form factors for some 1p-shell nuclei

The nucleon momentum distributions (NMD) and elastic electron scattering form factors of the ground state for 1p-shell nuclei with Z?=?N (such as ⁶Li, ¹⁰B, ¹²C and ¹⁴N nuclei) have been calculated in the framework of the coherent density fluctuation model (CDFM) and expressed in terms of the weight function $\left| {f( x )} \right|^2$ . The weight function has been expressed in terms of nucleon density distribution (NDD) of the nuclei and determined from the theory and the experiment. The feature of the long-tail behaviour at high-momentum region of the NMDs has been obtained by both the theoretical and experimental weight functions. The experimental form factors F(q) of all the considered nuclei are very well reproduced by the present calculations for all values of momentum transfer q. It is found that the contributions of the quadrupole form factors F _C2(q) in ¹⁰B and ¹⁴N nuclei, which are described by the undeformed p-shell model, are essential for obtaining a remarkable agreement between the theoretical and experimental form factors.     

Extraction of nuclear coupling constants from data on nuclear charge form factors

A possibility of extracting nuclear coupling constants from data on nuclear charge form factors is discussed. The method exploits analytic properties of form factors in the momentum transfer plane. As an illustration the form factor of⁴He is considered in detail. In this case the value \(g_{4_{He^3 He(^3 H)} }^2 /4\pi = 16 \pm 1\) has been obtained in excellent agreement with earlier determinations by means of other methods. Similar analysis of the¹⁶O form factor yields the first estimate of the oxygen-nucleon coupling∶ \(g_{16_{O^{15} O(^{15} N)N} }^2 /4\pi = 64\) .     

On magnetic dipole form factors in deformed nuclei

Properties of magnetic dipole form factors for deformed nuclei are discussed in terms of the angular momentum projected Hartree-Fock-Bogoljubov approximation and the neutron-proton interacting boson model. It is pointed out that there exists a relation between the M1 form factor for the excitation of the orbital K^π=1⁺ band, the M1 form factor for the ground-state band, and the collective M1 form factor in odd-A nuclei.     

Multiplicities for evaporative4He emission in heavy ion reactions: Relationships to spin and lifetime expectancy of the composite nucleus

Multiplicities are compared for⁴He evaporation in reactions of⁴⁰Ar and⁵⁶Fe projectiles (8.5 MeV/u) with with^natAg and²³⁸U targets. Coincidence requirements involving fusion-fission and projectile-like fragments have been used to select separate entrance-channel spin zones. Evaporation-like⁴He emission from the composite nuclei is shown to be large for mean spins ≦100?, and to decrease dramatically with increasing spin. Coincidence measurements between two⁴He particles have also been studied for⁴⁰Ar+^natAg. This requirement is shown to select reactions that lead to evaporation residues and therefore to a zone of relatively low spin. The shapes of the⁴He spectra provide an interesting probe of the mechanism and also of the thermodynamic properties of hot nuclei.     

The six-quark-admixture in the form factor of the3He at large transfer momenta

Elastic form factor of the³He nucleus is analysed with the use of Gaussian-type and realistic nuclear wave functions with a contribution of six-quark admixtures taken into account. The latter has been chosen so as to describe the data of analysis of cumulative and other processes and it amounts to about 8%. It is shown that unlike the deuteron form factor for³He the quark-nucleon interference is essential. The six-quark admixture does not remove the second minimum in the form factor of³He as a three-nucleon system atq ²~50 fm^?2. The comparison with other theoretical models and available experimental data is performed.     

Polarized parity violating electron scattering on 3He

We calculate the asymmetry parameters, A, and figures-of-merit for polarized parity violating electron scattering from ³He via the reaction, e⁻ +³ He → e⁻ +³ He. We do this explicitly forv incident electron energies of 1.0 GeV and 4.0 GeV. We find a sharp and unexpected variation in A due to cancellations between the weak and electromagnetic form factors caused by the different q² dependences of these form factors. We find that at small angles, the asymmetry may be obtained to reasonably high accuracy for all energies considered and that the interesting region where the asymmetry has its first maximum and minimum is accessible for electron energies of 1 GeV or higher. In addition we find that the asymmetry and figures-of-merit are in the range of those for other proposed target nuclei. We also consider the possibility of strange quark contributions to the asymmetry and show that at the first maxima and minima, possible contributions of the strange quark current vector form factors cause large variations in the asymmetry which might be observed.     

Charge form factor and cluster structure of the 6Li nucleus

The charge form factor of the 6Li nucleus is considered on the basis of its cluster structure. The charge density of ⁶Li is presented as a superposition of two terms. One of them is a folded density and the second one is a sum of the ⁴He and deuteron densities. Using the available experimental data for ⁴He and deuteron charge form factors, a satisfactory agreement of the calculations within the suggested scheme is obtained with the experimental data for the charge form factor of ⁶Li, including those in the region of large transferred momenta.      

Studies of single neutron holes in the transitional nuclei N = 83–89:: The 150, 148Nd(d,t) and 150, 148, 146Nd(3He, α) pick-up reactions

The level structures of the ^{145, 147, 149}Nd nuclei up to about 5 MeV excitation energy have been investigated with the (³He, α) reaction at 24 MeV. Additional 17 MeV (d, t) data have been obtained for ^{147, 149}Nd. The angular distributions have been analyzed with standard DWBA calculations, and spectroscopic factors have been deduced. Two groups of states carrying h_{$\text{11}\text{2}$} single-particle strength may be associated with the $\text{9}\text{2}$^? [514] and $\text{11}\text{2}$^? [505] Nilsson orbitals. A considerable amount of high-l single-particle strength may be found in the continuum observed in the (³He, α) spectra above 3 MeV in all the nuclei.