arXiv subjects

Satoru Hirenzaki

Publications and source records attributed to Satoru Hirenzaki.

31 records · Page 2Linked to original sources

arXiv2012

$η^\prime$ meson under partial restoration of chiral symmetry in nuclear medium

In-medium modification of the eta' mass is discussed in the context of partial restoration of chiral symmetry in nuclear medium. We emphasize that the U_A(1) anomaly effects causes the eta'-eta mass difference necessarily through the chiral symmetry breaking. As a consequence, the eta' 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 eta' mass generation eventually implies that there should be also a strong attractive interaction in the scalar channel of the eta'-N two-body system. We find that the attraction can be strong enough to form a bound state.

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arXiv2012

Spectroscopy of eta' mesic nuclei with (p,d) reaction

We are going to perform an inclusive spectroscopy experiment of eta' mesic nuclei with the 12C(p,d) reaction to study in-medium properties of the eta' meson. In nuclear medium, the eta' meson mass may be reduced due to partial restoration of chiral symmetry. In case of sufficiently large mass reduction and small absorption width of eta' at normal nuclear density, peak structures of eta' mesic states in 11C will be observed near the eta' emission threshold even in an inclusive spectrum. The experiment will be carried out at GSI with proton beam supplied by SIS using FRS as a spectrometer. The detail of the experiment is described.

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arXiv2012

Spectroscopy of eta'-nucleus bound states at GSI-SIS

The eta' meson mass may be reduced due to partial restoration of chiral symmetry. If this is the case, an eta'-nucleus system may form a nuclear bound state. We plan to carry out a missing-mass spectroscopy with the 12C(p,d) reaction at GSI-SIS. Peak structures corresponding to such a bound state may be observed even in an inclusive measurement, if the decay width is narrow enough.

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arXiv2012

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

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.

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arXiv2012

eta' meson under partial restoration of chiral symmetry in nuclear medium

We shed light upon the eta' mass in nuclear matter in the context of partial restoration of chiral symmetry, pointing out that the U_{A}(1) anomaly effects causes the eta'-eta mass difference necessarily through the chiral symmetry breaking. As a consequence, it is expected that the eta' mass is reduced by order of 100 MeV in nuclear matter where partial restoration of chiral symmetry takes place. The discussion given here is based on Ref. [1].

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arXiv2012

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

The in-medium mass of the $η^{\prime}$ meson is discussed in a context of partial restoration of chiral symmetry in nuclear medium. The $η^{\prime}$ 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 $η^{\prime}$ mass induced by partial restoration of chiral symmetry. This strong attraction in $η^{\prime}$ nuclear systems does not accompany large absorption of $η^{\prime}$ into nuclear matter. This leads to the possibility of so narrow bound states of the $η^{\prime}$ meson in nuclei to be seen in hadronic reactions with light nuclear targets.

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arXiv2011

Eta-prime bound states in nuclei and partial restoration of chiral symmetry

We discuss the in-medium mass of the eta-prime meson under partial restoration of chiral symmetry. The chiral SU(3)\otimes SU(3) symmetry tells us the flavor singlet pseudoscalar meson eta-prime should degenerate with the octet $η$ meson in the SU(3) flavor limit, when chiral symmetry is restored in spite of U(1)A anomaly in the flavor single axial current. The suppression of the anomaly effect induces an order of 100 MeV reduction for the eta-prime mass at the saturation density without introducing a large absorption width. We show the formation spectrum of the eta-prime mesonic bound state in a nucleus as a possible observation of the eta-prime mass reduction.

hep-ph↗

arXiv2011

Precision Spectroscopy of Deeply Bound Pionic Atoms and Partial Restoration of Chiral Symmetry in Medium

We study theoretically the formation spectra of deeply bound pionic atoms expected to be observed by experiments with high energy resolution at RIBF/RIKEN, and we discuss in detail the possibilities to extract new information on the pion properties at finite density from the observed spectra, which may provide information on partial restoration of chiral symmetry in medium. We find that the non-yrast pionic states such as 2s are expected to be seen in the (d,3He) spectra, which will be helpful to reduce uncertainties of the theoretical calculations in the neutron wave functions in nucleus. The observation of the 2s state with the ground 1s state is also helpful to reduce the experimental uncertainties associated in the calibration of the absolute excitation energy. We find that the nuclear densities probed by atomic pions are quite stable and almost constant for various atomic states and various nuclei. Effects of the pion wave function renormalization to the formation spectra are also evaluated.

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arXiv2006

Kaon Absorption from Kaonic Atoms and Formation Spectra of Kaonic Nuclei

We considered the kaon absorption from atomic states into nucleus. We found that the nuclear density probed by the atomic kaon significantly depends on the kaon orbit. Then, we reexamined the meanings of the observed strengths of one-body and two-body kaon absorption, and investigated the effects to the formation spectra of kaon bound states by in-flight ($K^-,p$) reactions. As a natural consequence, if the atomic kaon probes the smaller nuclear density, the ratio of the two-body absorption at nuclear center is larger than the observed value, and the depth of the imaginary potential is deeper even at smaller kaon energies as in kaonic nuclear states because of the large phase space for the two-body processes.

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arXiv2006

η- and η'-mesic nuclei and U_A(1) anomaly at finite density

We discuss theoretically the possibility of observing the bound states of the ηand η'(958) mesons in nuclei. We apply the NJL model to study the ηand η' meson properties at finite density and calculate the formation cross sections of the ηand η' bound states with the Green function method for (γ,p) reaction. We also discuss the experimental feasibility at photon facilities like SPring-8. The contributions due to the ωmeson production are also included to obtain the realistic (γ,p) spectra. We conclude that we can expect to observe resonance peaks in (γ,p) spectra for the formation of meson bound states and we can deduce new information on ηand η' properties at finite density. These observations are believed to be essential to know the possible mass shift of η' and deduce new information on the effective restoration of the U_A(1) anomaly in the nuclear medium.

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arXiv2005

Formation of Kaonic Atoms and Kaonic Nuclei by In-flight ($K^-,p$) reactions

We study the kaonic atom and kaonic nucleus formation by the in-flight ($K^-, p$) reactions for C, O, Si and Ca target cases theoretically. Deeply bound kaonic atoms were predicted to exist as quasi-stable states and were expected to be observed in some proper experimental methods. Kaonic nuclear states are also expected to exist with large decay widths. We evaluate the formation cross sections of the kaonic atoms and kaonic nuclei using an effective number approach. We show that the indications of the kaonic bound states can be observed in the outgoing proton energy spectra.

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arXiv2004

Formation of η'(958)-mesic nuclei and axial U_A(1) anomaly at finite density

We discuss the possibility to produce the bound states of the $η'(958)$ meson in nuclei theoretically. We calculate the formation cross sections of the $η'$ bound states with the Green function method for ($γ$,p) reaction and discuss the experimental feasibility at photon facilities like SPring-8. We conclude that we can expect to observe resonance peaks in ($γ$,p) spectra for the formation of $η'$ bound states and we can deduce new information on $η'$ properties at finite density. These observations are believed to be essential to know the possible mass shift of $η'$ and deduce new information of the effective restoration of the chiral $U_A(1)$ anomaly in the nuclear medium.

hep-ph↗

arXiv2002

Transposition of a local-density-dependent pion-nucleus potential to an effective density-linear potential - generalized Seki-Masutani relations

We have shown that a local-density-dependent term, $F[ρ(r)] ρ(r)$, of the pion-nucleus potential with a nuclear density, $ρ(r)$, can be transposed to a conventional density-linear term, $F(ρ_e) ρ(r)$, with an effective nuclear density, $ρ_e$, which is close to $\sim 0.6 ρ(0)$ for most $π^-$ bound states. The presently found relations, {\it generalized Seki-Masutani relations}, for the density-quadratic term, the medium-modified isovector term and the double-scattering isoscalar term of the s-wave pion-nucleus interaction assure that the constant parameters in the conventional pion-nucleus potential are interpreted as being effective ones in the light of density-dependent effects.

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