Kazuo Tsushima

Variation of hadron masses in finite nuclei

The quark-meson coupling model, based on a mean-field description of nonoverlapping nucleon bags bound by the self-consistent exchange of {sigma}, {omega}, and {rho} mesons, is extended to investigate the change of hadron properties in finite nuclei. Relativistic Hartree equations for spherical nuclei have been derived from a relativistic quark model of the structure of bound nucleons and mesons. Using this unified, self-consistent description of both infinite nuclear matter and finite nuclei, we investigate the properties of some closed-shell nuclei and study the changes in the hadron masses of the nonstrange vector mesons, the hyperons, and the nucleon in those nuclei. We find a new, simple scaling relation for the changes of the hadron masses, which can be described in terms of the number of nonstrange quarks in the hadron and the value of the scalar mean field in a nucleus. {copyright} {ital 1997} {ital The American Physical Society}

Nucleon and hadron structure changes in the nuclear medium and impact on observables

We study the effect of hadron structure changes in a nuclear medium using the quark-meson coupling (QMC) model. The QMC model is based on a mean field description of non-overlapping nucleon (or baryon) bags bound by the self-consistent exchange of scalar and vector mesons in the isoscalar and isovector channels. The model is extended to investigate the properties of finite nuclei, in which, using the Born-Oppenheimer approximation to describe the interacting quark-meson system, one can derive the effective equation of motion for the nucleon (or baryon), as well as the self-consistent equations for the meson mean fields. In conventional nuclear physics, the Skyrme effective forces are very popular, but, there is no satisfactory interpretation of the parameters appearing in the Skyrme forces. Comparing a many-body Hamiltonian generated by the QMC model in the zero-range limit with that of the Skyrme effective forces, it is possible to obtain a remarkable agreement between the Skyrme force and the QMC effective interaction. One can also investigate the relationship between the QMC model and Quantum Hadrodynamics, by carrying out a re-definition of the scalar field in matter. Furthermore, by using naive dimensional analysis, it is possible to see that the QMC model can provide remarkably natural coupling constants and hence the model itself is regarded as a natural effective field theory for nuclei. The model is first applied to nuclear matter, where the coupling constants are determined so as to produce the saturation condition at normal nuclear matter density. We find a new, simple scaling relation for the changes of hadron masses in a nuclear medium, which can be described in terms of the number of light quarks in a hadron and the value of the scalar mean-field in matter. Once the coupling constants are fixed, the model can be applied to various finite nuclei, including strange and exotic hypernuclei. In this article, we discuss in detail the properties of hypernuclei and meson-nucleus deeply bound states. It is also of great interest that the QMC model predicts a variation of the nucleon form factors in nuclear matter, which will affect certainly the analysis of electron scattering off nuclei, including polarization-transfer experiments. Recent experimental analysis of data taken at Jefferson Laboratory (JLab) and MAMI indeed seems to support such a variation of nucleon form factors in nuclei. The change of nucleon structure in a nuclear medium is also expected to modify nuclear structure functions (the nuclear EMC effect), which

Baryon masses from lattice QCD: Beyond the perturbative chiral regime

Consideration of the analytic properties of pion-induced baryon self-energies leads to new functional forms for the extrapolation of light baryon masses. These functional forms reproduce the leading non-analytic behavior of chiral perturbation theory, the correct non-analytic behavior at the

Self-consistent description of finite nuclei based on a relativistic quark model

N \pi

IN-MEDIUM ELECTRON-NUCLEON SCATTERING

threshold and the appropriate heavy-quark limit. They involve only three unknown parameters, which may be obtained by fitting to lattice data. Recent dynamical fermion results from CP-PACS and UKQCD are extrapolated using these new functional forms. We also use these functions to probe the limit of applicability of chiral perturbation theory to the extrapolation of lattice QCD results.

Charmed mesic nuclei

Abstract Relativistic Hartree equations for spherical nuclei have been derived from a relativistic quark model of the structure of bound nucleons which interact through the (self-consistent) exchange of scalar (σ) and vector (ω and ϱ) mesons. The coupling constants and the mass of the σ-meson are determined from the properties of symmetric nuclear matter and the rms charge radius in 40 Ca. Calculated properties of static, closed-shell nuclei from 16 O to 208 Pb are compared with experimental data and with results of Quantum Hadrodynamics (QHD). The dependence of the results on the nucleon size and the quark mass is investigated. Several possible extensions of the model are also discussed.

Binding of hypernuclei in the latest quark-meson coupling model

Abstract In-medium nucleon electromagnetic form factors are calculated in the quark meson coupling model. The form factors are typically found to be suppressed as the density increases. For example, at normal nuclear density and Q 2 ∼0.3 GeV 2 , the nucleon electric form factors are reduced by approximately 8% while the magnetic form factors are reduced by only 1–2%. These variations are consistent with current experimental limits but should be tested by more precise experiments in the near future.

σ and ω meson propagation in a dense nuclear medium

We show that the

Charmonium absorption by nucleons

{D}^{\ensuremath{-}}

Self-consistent description of Λ hypernuclei in the quark-meson coupling model

meson will form narrow bound states with