Satoru Hirenzaki

η′-Nucleus optical potential and possible η′ bound states

Abstract Starting from a recent model of the η ′ N interaction, we evaluate the η ′ -nucleus optical potential, including the contribution of lowest order in density, t ρ / 2 m η ′ , together with the second-order terms accounting for η ′ absorption by two nucleons. We also calculate the formation cross section of the η ′ bound states from ( π + , p ) reactions on nuclei. The η ′ -nucleus potential suffers from uncertainties tied to the poorly known η ′ N interaction, which can be partially constrained by the experimental modulus of the η ′ N scattering length and/or the recently measured transparency ratios in η ′ nuclear photoproduction. Assuming an attractive interaction and taking the claimed experimental value | a η ′ N | = 0.1 fm , we obtain an η ′ optical potential in nuclear matter at saturation density of V η ′ = − ( 8.7 + 1.8 i ) MeV , not attractive enough to produce η ′ bound states in light nuclei. Larger values of the scattering length give rise to deeper optical potentials, with moderate enough imaginary parts. For a value | a η ′ N | = 0.3 fm , which can still be considered to lie within the uncertainties of the experimental constraints, the spectra of light and medium nuclei show clear structures associated to η ′ -nuclear bound states and to threshold enhancements in the unbound region.

Medium effects to N(1535) resonance and eta mesic nuclei

The structure of eta-nucleus bound systems (eta mesic nuclei) is investigated as one of the tools to study in-medium properties of the N(1535) (N^*) resonance by using the chiral doublet model to incorporate the medium effects of the N^* resonance in a chiral symmetric way. We find that the shape and the depth of the eta-nucleus optical potential are strongly affected by the in-medium properties of the N^* and the nucleon. Especially, as a general feature of the potential, the existence of a repulsive core of the eta-nucleus potential at the nuclear center with an attractive part at the nuclear surface is concluded. We calculate the level structure of bound states in this central-repulsive and surface-attractive optical potential and find that the level structure is sensitive to the in-medium properties of the N^*. The (d,3He) spectra are also evaluated for the formation of these bound states to investigate the experimental feasibility. We also make comments on the possible existence of halo-like eta states in beta-unstable halo nuclei.

Pionic atom spectroscopy in the (d,3 He) reaction at finite angles

We study the formation of deeply bound pionic atoms in the (d, 3He) reactions theoretically and show the energy spectra of the emitted 3He at finite angles, which are expected to be observed experimentally. We find that the different combinations of the pion-bound and neutron-hole states dominate the spectra at different scattering angles because of the matching condition of the reaction. We conclude that the observation of the (d, 3He) reaction at finite angles will provide the systematic information of the pionic bound states in each nucleus and will help to develop the study of the pion properties and the partial restoration of chiral symmetry in nuclei.

η′ meson under partial restoration of chiral symmetry in nuclear medium

In-medium modification of the 0 mass is discussed in the context of partial restoration of chiral symmetry in nuclear medium. We emphasize that the UA(1) anomaly e ects causes the 0 - mass di erence necessarily through the chiral symmetry breaking. As a consequence, the 0 mass is expected to be reduced by order of 100 MeV in nuclear matter where about 30% reduction of chiral symmetry takes place. The strong attraction relating to the 0 mass generation eventually implies that there should be also a strong attractive interaction in the scalar channel of the 0 -N two-body system. We find that the attraction can be strong enough to form a

Study of possible omega bound states in nuclei with the (gamma,p) reaction

We perform calculations for {omega} production in nuclei by means of the ({gamma},p) reaction for photon energies and proton angles suited to currently running and future experiments in present laboratories. For some cases of possible {omega} optical potentials, we find that clear peaks are observable when a good resolution in the {omega} energy is available. We also study the inclusive production of {pi}{sup 0}{gamma} in nuclei around the {omega} energy and find a double hump structure for the energy spectra, with a peak around a {pi}{sup 0}{gamma} energy of m{sub {omega}}-100 MeV, which could easily be misidentified by a signal of an {omega} bound state in nuclei, while it is actually due to a different scaling of the uncorrelated {pi}{sup 0}{gamma} production and {omega} production with subsequent {pi}{sup 0}{gamma} decay.

Nuclear density probed by anti-kaon–nucleus systems and anti-kaon–nucleus interaction

Abstract Effective nuclear densities probed by anti-kaon–nucleus systems is studied theoretically both for bound and low energy scattering states. As for the bound states, we investigate kaonic atoms. We find that the effective density depends on the atomic states significantly and we have the possibility to obtain the anti-kaon properties at various nuclear densities by observing the several kaonic atom states. We also find the energy dependence of the probed density by scattering states. We find that the study of the effective nuclear density will help to find the proper systems to investigate the meson properties at various nuclear densities.

Structure and Formation of η‐ and π‐Nucleus Systems

In this article, we review recent research activities on the structure and formation of the η mesic nuclei and the pionic atoms.

Meson and Baryon resonances

In this talk I review recent advances on the structure of the meson and baryon resonances which can be dynamically generated from the interaction of mesons or mesons and baryons. Particular emphasis is put on results involving vector mesons, which bring new light into the nature of some of the observed higher mass mesons and baryons and make predictions for new states.