Response Function Of Nuclei Research Articles

Relativistic Spin-Isospin Dependent Response Function of Nucleus

A full relativistic formalism is employed to derive the relativistic particle-hole and delta-hole excitation polarization insertion of pion propagator in nuclear matter. The spin-isospin-dependent response function of nucleus at high energy-momentum transfer is calculated with the nuclear matter approximation. The short range correlation effect, two-nucleon absorption and nucleus form factor effects are included in the calculation. The position and width of the resonance peak of the spin-isospin mode are reproduced and found to be coincident with experiment data. The position of the peak and its width is sensitive to Landau-Migdal parameter g' which is about 0.6.

Antiparticle Excitation Effect in the Relativistic Spin-Isospin-Dependent Response Function of Nucleus**The project supported by National Natural Science Foundation of China (Grant No. 19775072), and by the Natural Science Foundation of Guangdong Province of China (Grant No. 970130)

The spin-isospin-dependent response function of nucleus is studied in the relativistic formalism. Besides the well-known relativistic particlehole and -hole excitations, the antiparticle excitations such as nucleon-antinucleon, nucleon-antidelta, antinucleon-delta excitations are also taken into account in the calculation of the response function, and the effect of the antiparticle excitation is emphasized. The antiparticle excitation enhances the response function and its effect to the response function is largely determined by the cutoff parameter which is introduced by the need of the renormalization. The position of the peak of the -hole resonance is mainly dominated by short range correlation Landau-Migdal parameter , and we find is about 0.6. The effect of two-nucleon absorption and projectiletarget form factor are also studied.

Inclusive electron-nucleus scattering at high momentum transfer.

The response function of nuclei in the quasielastic region at large momentum transfer (q\ensuremath{\le}10 ${\mathrm{fm}}^{\mathrm{\ensuremath{-}}1}$) is measured for a series of nuclei, $^{4}\mathrm{He}$, $^{12}\mathrm{C}$, $^{27}\mathrm{Al}$, $^{56}\mathrm{Fe}$, and $^{197}\mathrm{Au}$, up to large values of the Bjorken scaling variables x2.5.

Δ Excitations in nuclei and the coherent pion decay

The Δ excitations in nuclei induced by intermediate energy charge exchange reactions are analyzed within the isobar-hole model. It is shown that the isovector spin-longitudinal (S · qT) response function of nuclei in the Δ resonance region is shifted down in energy by ~ 60 MeV in comparison to the spin-transverse (S × qT) response function. This shift is consistent with pion and photon total cross section data. The coherent pion decay of the Δ resonance is studied by means of the 12C(p, nπ+)12C(g.s.) coincidence reaction. The calculations show that the coherent pion production cross section provides a unique signature on the nuclear pionic mode. The coherent pions have a peak energy of E = 250 MeV and a strongly forward peaked angular distribution.

Manifestation of ground-state correlation in momentum distribution and response function

A relation is studied between the momentum distribution and the response function of nuclei in the quasielastic region. It is shown that a consistent treatment of the ground-state correlation leads simultaneously to (i) the existence of the high-momentum tail of the momentum distribution and to (ii) a quenching of the response function around the quasielastic peak region and an enhancement of the high-energy tail part, i.e. they are two different manifestations of the ground-state correlation.