Green's function Monte Carlo calculations of magnetic moments and M1 transitions including two-body meson-exchange current (MEC) contributions are reported for A<=7 nuclei. The realistic Argonne v18 two-nucleon and Illinois-2 three-nucleon potentials are used to generate the nuclear wave functions. The two-body meson-exchange operators are constructed to satisfy the continuity equation with the Argonne v18 potential. The MEC contributions increase the A=3,7 isovector magnetic moments by 16% and the A=6,7 M1 transition rates by 17--34%, bringing them into very good agreement with the experimental data.
The structure and the energy spectrum of the $η^{\prime}$ mesonic nuclei are investigated in a relativistic mean field theory. One expects a substantial attraction for the $η^{\prime}$ meson in finite nuclei due to the partial restoration of chiral symmetry in the nuclear medium. Such a hadronic scale interaction for the $η^{\prime}$ mesonic nuclei may provide modification of the nuclear structure. The relativistic mean field theory is a self-contained model for finite nuclei which provides the saturation property within the model, and is good to investigate the structure change of the nucleus…
Microscopics of meson degrees of freedom in nucleons and mesons in nuclei - what can be seen in the process of quasielastic knockout of mesons by high-energy electrons
We present a selection of the first results obtained in a comprehensive calculation of ground state properties of even-even superheavy nuclei in the region of 96 < Z < 136 and 118 < N < 320 from the Quark-Meson-Coupling model (QMC). Ground state binding energies, the neutron and proton number dependence of quadrupole deformations and Q$_α$ values are reported for even-even nuclei with 100 < Z < 136 and compared with available experimental data and predictions of macro-microscopic models. Predictions of properties of nuclei, including Q$_α$ values, relevant for planning future experiments are p…
Recent topics on mesons in nuclei are discussed by especially emphasizing the role of the partial restoration of chiral symmetry in the nuclear medium. The spontaneously broken chiral symmetry in vacuum is considered to be incompletely restored in finite nuclear density systems with moderate reduction of the magnitude of the quark condensate. On the partial restoration of chiral symmetry, the wave function renormalization is important to be taken into account for the Nambu-Goldstone bosons. We also discuss the possible change of the meson properties in the nuclear medium and meson-nucleus syst…
After some short introductory remarks on particular issues on the vector mesons in nuclei, in this paper we present a short review of recent developments concerning the interaction of vector mesons with baryons and with nuclei from a modern perspective using the local hidden gauge formalism for the interaction of vector mesons. We present results for the vector baryon interaction and in particular for the resonances which appear as composite states, dynamically generated from the interaction of vector mesons with baryons, taking also the mixing of these states with pseudoscalars and baryons in…
Recent theoretical developments of hadrons in nuclei are briefly reviewed in the aspect of chiral symmetry in nuclei. We show a general sum rule connecting in-medium hadronic quantities and quark condensate, emphasizing that both pionic mode and particle-hole excitations in the nuclear medium are responsible for reduction of the chiral condensate in nuclear matter. We also discuss that few-body nuclear systems with kaons are good objects to investigate basic features of kaon-nucleus interactions, showing recent understandings of the structure of Lambda(1405) and possible bound states of KbarNN…
The contribution of the tensor meson $K_2^*(1430)$ exchange in the process $γp\to K^+Λ(Σ^0)$ is investigated within the Regge framework. Inclusion of the $K_2^*$ exchange in the $K(494)+K^*(892)$ exchanges with the coupling constants chosen from the SU(3) symmetry leads to a better description of the production mechanism without referring to any fitting procedure. This shows the significance of the role of the tensor meson exchange to have the Regge theory basically free of parameters with the SU(3) symmetry a good approximation for the meson-baryon couplings.
The energy transfer spectra have been calculated for the coherent $η$ meson production in the proton nucleus reaction. The elementary reaction occurring in the nucleus is considered as $ pN \to pN^*(1535) $; $ N^*(1535) \to Nη$. The $N^*(1535)$ excitation for the forward going proton and $η$ meson is occurred due to the $π^0$ and $η$ meson exchange interactions, other mesons do not contribute in this process. The cross sections are calculated for the $π^0$ and $η$ meson exchange interactions, and the effect of their interference on the cross section is also studied. The initial and final state…
Recent developments in the relativistic nuclear field theory (RNFT) are reviewed. Based on the covariant meson-nucleon Lagrangian of quantum hadrodynamics, RNFT connects consistently the high-energy scale of heavy mesons, medium-energy range of pion and the low-energy domain of emergent collective vibrations (phonons) in a parameter-free way. Mesons and phonons build up the effective interaction in various channels, in particular, the phonon-exchange part takes care of the retardation effects, which are of great importance for the fragmentation of single-particle states, spreading of collectiv…
We investigate the $ϕ$ meson nuclear transparency using some recent theoretical developments on the $ϕ$ in medium self-energy. The inclusion of direct resonant $ϕN$-scattering and the kaon decay mechanisms leads to a $ϕ$ width much larger than in most previous theoretical approaches. The model has been confronted with photoproduction data from CLAS and LEPS and the recent proton induced $ϕ$ production from COSY finding an overall good agreement. The results support the need of a quite large direct $ϕN$-scattering contribution to the self-energy.
This is the contribution to the proceedings of the MENU 2010 conference. The recent work of Ref. [7] is summarized. Elastic piN scattering and the reaction pi^+ p --> K^+ Sigma^+ are described simultaneously in a unitary coupled-channels approach which respects analyticity. SU(3) flavor symmetry is used to relate the t- and u- channel exchanges that drive the meson-baryon interaction in the different channels. Angular distributions, polarizations, and spin-rotation parameters are compared with available experimental data. The pole structure of the amplitudes is extracted from the analytic cont…
Back in the mid eighties, a new branch of investigation which was related to the interaction of eta mesons with nuclei came into existence. It started with the theoretical prediction of possible exotic states of eta mesons and nuclei bound by the strong interaction and later developed into an extensive experimental program to search for such unstable states as well as understand the underlying interaction via eta meson producing reactions. The vast literature of experimental as well as theoretical works which studied various aspects of eta producing reactions such as the $π^+$ $n$ $\to ηp$, $p…
We have calculated the total cross section for k^+-4^He, 16^O, 40^Ca, intes at incident momenta of the kaon P_lab<1GeV . We derived the K^+-nucleon optical potential according to the exchange of 3- mesons (segma,roh,omega) and also for 4- (segma,roh,omega, segma_0) exchanged between the reactants. We showed both of the radial behavior of the real and the imaginary parts of the derived potential. Comparisons between the available experimental data, other theoretical work and the calculated total cross sections for the three studied nuclei which have shown a reasonable agreement. The extended fo…
A meson-exchange model of the associated photoproduction of vector mesons and N*(1440) resonances
我们讨论了质子在特定通道中光生ω-和ρ 0-介子的情况，其中靶质子被激发到Roper共振N*（1440）。我们提出了一个简单的介子交换模型，这些过程，以评估其截面阈值附近和低动量转移。特别建议，在这些运动学条件下，ρ 0介子和Roper共振的相关光生的微分截面可以提供关于N*（1440）的标量-等激激发强度的直接信息，从而提供关于有效的σ N N*（1440）耦合的大小的直接信息。后一个量是鲜为人知的，对核多体问题很感兴趣。
