Correlations and spectral functions in asymmetric nuclear matter

The self-energy of nucleons in asymmetric nuclear matter is evaluated employing different realistic models for the nucleon-nucleon interaction. Starting from the Brueckner Hartree Fock approximation without the usual angle-average in the two-nucleon propagator the effects of the hole-hole contributions are investigated within the self-consistent Green's function approach. Special attention is paid to the isospin-dependence of correlations, which can be deduced from the spectral functions of nucleons in asymmetric matter. The strong components of the proton - neutron interaction lead in neutron-rich matter to a larger depletion for the occupation probability of proton states below the Fermi momentum.Comment: 11 pages, 5 figure

Spectral function at high missing energies and momenta

The nuclear spectral function at high missing energies and momenta has been determined from a self-consistent calculation of the Green's function in nuclear matter using realistic nucleon-nucleon interactions. The results are compared with recent experimental data derived from ($e,e'p$) reactions on $^{12}C$. A rather good agreement is obtained if the Green's functions are calculated in a non-perturbative way.Comment: 10 pages, 3 figure

Properties of asymmetric nuclear matter in different approaches

Properties of asymmetric nuclear matter are derived from various many-body approaches. This includes phenomenological ones like the Skyrme Hartree-Fock and relativistic mean field approaches, which are adjusted to fit properties of nuclei, as well as more microscopic attempts like the Brueckner-Hartree-Fock approximation, a self-consistent Greens function method and the so-called $V_{lowk}$ approach, which are based on realistic nucleon-nucleon interactions which reproduce the nucleon-nucleon phase shifts. These microscopic approaches are supplemented by a density-dependent contact interaction to achieve the empirical saturation property of symmetric nuclear matter. The predictions of all these approaches are discussed for nuclear matter at high densities in $\beta$-equilibrium. Special attention is paid to behavior of the isovector component of the effective mass in neutron-rich matter.Comment: 16 pages, 7 figure

Tensor target spin asymmetries in incoherent π−-photoproduction off the deuteron including rescattering effects

Tensor target spin asymmetries [Formula: see text] ([Formula: see text]=0,1,2) in the reaction [Formula: see text] are studied for photon energies from [Formula: see text]-threshold up to 1.5[Formula: see text]GeV with inclusion of rescattering effects. It is shown that the influence of rescattering effects on the tensor target spin asymmetries is sizable in the energy region near [Formula: see text]-threshold. At higher energies, much smaller influence of rescattering effects is seen. The sensitivity of the obtained results to the elementary pion photoproduction operator is investigated and a considerable dependence is found, in particular at forward pion angles. In addition, a comparison with results of other theoretical models is also given. The extracted spin asymmetries are compared with available experimental data and a qualitative agreement is obtained. The predictions presented here may be useful to interpret the recent measurements from the VEPP-3 electron storage ring. </jats:p