H. Nagahiro

Formation of

We calculate theoretically the formation spectra of eta(958)-nucleus systems in the (p,d) reaction for the investigation of the in-medium modification of the eta mass. We show the comprehensive numerical calculations based on a simple form of the eta optical potential in nuclei with various potential depths. We conclude that one finds an evidence of possible attractive interaction between eta and nucleus as peak structure appearing around the eta threshold in light nuclei such as 11C when the attractive potential is stronger than 100 MeV and the absorption width is of order of 40 MeV or less. Spectroscopy of the (p,d) reaction is expected to be performed experimentally at existing facilities, such as GSI. We also estimate the contributions from the omega and phi mesons, which have masses close to the eta meson, concluding that the observation of the peak structure of the eta-mesic nuclei is not disturbed although their contributions may not be small.

\eta^\prime(958)

A novel method is proposed to measure eta(958) meson bound states in 11C nuclei by missing mass spectroscopy of the 12C(p,d) reaction near the eta production threshold. It is shown that peak structures will be observed experimentally in an inclusive measurement in case that the in-medium eta mass reduction is sufficiently large and that the decay width of eta mesic states is narrow enough. Such a measurement will be feasible with the intense proton beam supplied by the SIS synchrotron at GSI combined with the good energy resolution of the fragment separator FRS.

-mesic nuclei by (

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.

p,d

The radiative decay of the axial-vector resonances into a pseudoscalar meson and a photon is studied using the vector meson Lagrangian obtained from the hidden gauge symmetry (HGS) formalism. The formalism is well suited to study this problem since it deals with pseudoscalar and vector mesons in a unified way, respecting chiral invariance. We show explicitly the gauge invariance of the set of diagrams that appear in the approach and evaluate the radiative decay width of the a{sub 1}(1260) and b{sub 1}(1235) axial-vector meson resonances into {pi}{gamma}. We also include the contribution of loops involving anomalous couplings and compare the results to those obtained previously within another formalism.

) reaction

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.

Feasibility Study of Observing η' Mesic Nuclei with (p,d) Reaction

The in-medium mass of the

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

eta^{prime}

Hidden gauge formalism for the radiative decays of axial-vector mesons

meson is discussed in a context of partial restoration of chiral symmetry in nuclear medium. The

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

eta^{prime}

Nuclear bound state of eta'(958) and partial restoration of chiral symmetry in the eta' mass

mass is expected to be reduced by order of 100 MeV at the saturation density. The reduction is a consequence of the suppression of the anomaly effect on the