We present a model for the study of the excitation of Δ(1232) and N*(1440) resonances in isobaric charge-exchange (AZ, A(Z ± 1)) reactions of heavy nuclei. Quasi-elastic and inelastic elementary ...processes contributing to the double differential cross sections of the reactions are described in terms of the exchange of virtual pions. The inelastic channel includes processes where the resonances are excited both in the target and in the projectile nucleus. We present results for reactions of 112Sn and 124Sn on different targets. Our results confirm that the position of the Δ peak is insensitive to targets with mass number A ≥ 12, and show that the origin of the Δ peak shift towards low excitation energies, with respect to its position in reactions with a proton target, can be easily explained in terms of the superposition of the different excitation mechanisms contributing to the reaction.
A theoretical method incorporating the density functional theory and quasiparticle-phonon model is applied for systematic study of low-energy excitations of different multipolarities related to ...neutron or proton skins in stable and exotic nuclei. Furthermore, the unique character of the observed excitations identified with pygmy dipole or pygmy quadrupole resonances is confirmed in quasiparticle-random-phase-approximation plus multiphonon calculations. The achievements of the multiphonon approach for description of pygmy and other strengths are discussed.
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We suggest new methods to extract elastic (quasi-elastic) scattering angular distribution and reaction (capture) cross sections from the experimental elastic (quasi-elastic) backscattering ...excitation function taken at a single angle. A novel Coulomb scattering relation between angular momentum and centrifugal energy is used. The methodology is developed for addressing complementary reaction observables, improving the description of elastic differential cross section.
We present an extensive experimental study of the recently predicted pygmy quadrupole resonance (PQR) in Sn isotopes, where complementary probes were used. In this study, (α,α′γ) and (γ,γ′) ...experiments were performed on 124Sn. In both reactions, Jπ=2+ states below an excitation energy of 5 MeV were populated. The E2 strength integrated over the full transition densities could be extracted from the (γ,γ′) experiment, while the (α,α′γ) experiment at the chosen kinematics strongly favors the excitation of surface modes because of the strong α-particle absorption in the nuclear interior. The excitation of such modes is in accordance with the quadrupole-type oscillation of the neutron skin predicted by a microscopic approach based on self-consistent density functional theory and the quasiparticle-phonon model (QPM). The newly determined γ-decay branching ratios hint at a non-statistical character of the E2 strength, as it has also been recently pointed out for the case of the pygmy dipole resonance (PDR). This allows us to distinguish between PQR-type and multiphonon excitations and, consequently, supports the recent first experimental indications of a PQR in 124Sn.
Pairing across the particle emission threshold and the properties of corresponding quasiparticle strength functions are discussed in an extended mean-field approach. This particular type of dynamical ...correlations gives rise to a unique class of sharp low-lying resonances close to the particle emission threshold. Spectral functions for particle and hole states are discussed. They are explored theoretically by single-nucleon transfer reactions, populating the low energy continuum with respect to a core nucleus. The cross sections of the reaction d(9Li, 10Li)p at Tlab=2.36 AMeV, recently measured at REX-ISOLDE, are well reproduced by our calculations including a pairing resonance in the 3/2− partial wave of purely coupled channels nature.
We calculate the modification of a rho meson in nuclear matter through its coupling to resonance-hole states. Starting from a recently proposed model, we include all four star resonances up to 1.9 ...GeV. In contrast to previous works, we include not only resonances that couple to the rho in a relative
p-wave, but also those that couple to an
s-wave state. In addition, we solve the equation for the rho spectral function self-consistently. We find that
s-wave resonances affect the in medium spectral function of the rho strongly. In the transverse channel the rho meson is, especially at non-zero momentum, completely washed out and can in the presence of nuclear matter no longer be viewed as a resonant excitation of the vacuum. Instead, our model shows a continuum of possible excitations with the quantum numbers of a transversely polarized rho. In the longitudinal channel, however, the rho retains its resonant character in our calculation. As a consequence of the self-consistent treatment we also find a strong enhancement of the widths of the included nucleon resonances in medium.
(ProQuest: ... denotes formulae and/or non-USASCII text omitted)We study the charmed meson pair (D super(0)D super(0) and D super(+)D super(-)) production in pp annihilation within an effective ...Lagrangian model that has only the baryon-meson degrees of freedom and involves the physical hadron masses. The reaction amplitudes include terms corresponding to the t-channel ..., ..., and ... baryon exchanges and the s-channel excitation, propagation and decay of the Psi(3770) resonance into the charmed mesons. The initial- and final-state distortion effects have been accounted for by using a simple eikonal approximation-based procedure in the same way as was done in our previous study of the ... reaction within a similar model. The D super(0)D super(0) production reaction is dominated by the ... baryon exchange process and the corresponding total cross sections are predicted to be in the range of 0.18?0.7 mu b for antiproton beam momenta varying between threshold and 20GeV/c. The Psi(3770) resonance contributions have a large influence on the differential cross sections of the D super(-)D super(+) production reaction.
We perform Glauber model calculations of the antiproton–nucleus elastic and quasielastic scattering and absorption in the beam momentum range ∼0.5÷10 GeV/c. A good agreement of our calculations with ...available LEAR data and with earlier Glauber model studies of the p¯A elastic scattering allows us to make predictions at the beam momenta of ∼10 GeV/c, i.e. at the regime of the PANDA experiment at FAIR. The comparison with the proton–nucleus elastic scattering cross sections shows that the diffractive minima are much deeper in the p¯A case due to smaller absolute value of the ratio of the real-to-imaginary part of the elementary elastic amplitude. Significant polarization signal for p¯A elastic scattering at 10 GeV/c is expected. We have also revealed a strong dependence of the p¯A absorption cross section on the slope parameter of the transverse momentum dependence of the elementary p¯N amplitude. The p¯A optical potential is discussed.
The study of a fully quantum mechanical description of coherent meson production in antinucleon annihilation on nuclei is presented. Two different reaction mechanisms are presented including initial ...and final state interactions, which are both derived from a folding approach. The underlying fundamental antinucleon-nucleon NN and pion-nucleon piN interactions enter into the optical potentials, which are folded with Hartree-Fock-Bogoliubov nuclear densities. Existing approaches to pion nucleus interactions have been extended to higher energies beyond the Delta -resonance. Cross sections are shown.
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