arXiv subjects

Yoshiko Kanada-En'yo

Publications and source records attributed to Yoshiko Kanada-En'yo.

At least 37 records · Page 2Linked to original sources

arXiv2020

Binding of antikaons and Lambda(1405) clusters in light kaonic nuclei

The energy spectra of light-mass kaonic nuclei were investigated using the theoretical framework of the $0s$-orbital model with zero-range $\bar{K} N$ and $\bar{K}\bar{K}$ interactions of effective single-channel real potentials. The energies of the $\bar{K} NN$, $\bar{K} NNN$, $\bar{K} NNNN$, $\bar{K}\bar{K} N$, and $\bar{K}\bar{K} NN$ systems were calculated in the cases of weak- and deep-binding of the $\bar{K} N$ interaction, which was adjusted to fit the $Λ(1405)$ mass with the energy of the $\bar{K} N$ bound state. The results qualitatively reproduced the energy systematics of kaonic nuclei calculated via other theoretical approaches. In the energy spectra of the $\bar{K} NN$ and $\bar{K}\bar{K} NN$ systems, the lowest states $\bar{K} NN(J^π,T=0^-,1/2)$ and $\bar{K}\bar{K} NN(0^+,0)$ were found to have binding energies approximately twice and four times as large as that of the $\bar{K} N(1/2^-,0)$ state, respectively. Higher $(J^π,T)$ states including $\bar{K} NN(1^-,1/2)$, $\bar{K}\bar{K} NN(0^+,1)$, and $\bar{K}\bar{K} NN(1^+,1)$ were predicted at energies of 9--25 MeV below the antikaon-decay threshold. The effective $Λ(1405)$-$Λ(1405)$ interaction in the $\bar{K}\bar{K} N N$ system was also investigated via a $\bar{K} N+\bar{K} N$-cluster model. Strong and weak $Λ(1405)$-$Λ(1405)$ attractions were obtained in the $S^π=0^+$ and $S^π=1^-$ channels, respectively. The $Λ(1405)$-$Λ(1405)$ interaction in the $$\bar{K}\bar{K} NN$ system was compared with the effective $d$-$d$ interaction in the $NNNN$ system, and the properties of dimer-dimer interactions in hadron and nuclear systems were discussed.

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arXiv2020

Effective interactions between nuclear clusters

The effective interactions between two nuclear clusters, $d+d$, $t+t$, and $α+α$, are investigated within a cluster model using local nucleon-nucleon~($NN$) forces. It is shown that the interaction in the spin-aligned $d+d$ system is repulsive for all inter-cluster distances, whereas the $α+α$ and spin-aligned $t+t$ systems are attractive at intermediate distances. The Pauli blocking between identical-nucleon pairs is responsible for the cluster-cluster repulsion and becomes dominant in the shallow binding limit. We demonstrate that two $d$-clusters could be bound if the $NN$ force has nonzero range and is strong enough to form a deeply bound $d$-cluster, or if the $NN$ force has both even-parity and odd-parity attraction. Effective dimer-dimer interactions for general quantum systems of two-component fermions are also discussed in heavy-light mass limit, where one component is much heavier than the other, and their relation to inter-cluster interactions in nuclear systems are discussed. Our findings provide a conceptual foundation for conclusions obtained numerically in the literature, that increasing the range or strength of the local part of the attractive nucleon-nucleon interaction results in a more attractive cluster-cluster interaction.

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arXiv2020

Microscopic calculation of proton and alpha-particle inelastic scattering to study the excited states of $^{6}$He and $^{8}$He

Elastic and inelastic cross sections of the $p+{}^6\textrm{He}$, $p+{}^8\textrm{He}$, and $α+{}^8\textrm{He}$ reactions were investigated using the Melbourne $g$-matrix folding approach with the theoretical densities of ${}^6\textrm{He}$ and ${}^8\textrm{He}$ obtained by a microscopic structure model of antisymmetrized molecular dynamics (AMD). Microscopic coupled-channel (MCC) calculations of the $p+{}^6\textrm{He}$ and $p+{}^8\textrm{He}$ reactions were performed to investigate transition properties of the ${}^6\textrm{He}(2^+_1)$ and ${}^8\textrm{He}(2^+_1)$ states. The MCC+AMD calculations reproduced elastic cross sections of the $p+{}^6\textrm{He}$ reaction at $E=40.9$ MeV/A and of the $p+{}^8\textrm{He}$ reaction at $E=32.5$ and 72 MeV/A, which have both been measured by inverse kinematics experiments. For $p+{}^6\textrm{He}$ inelastic scattering to the $2^+_1$ state, the calculated result was in reasonable agreement with the $(p,p')$ data at $E=24.5$ and 40.9 MeV/A and supported the AMD prediction of the neutron transition matrix element $M_n=7.9$ fm$^2$. For the $p+{}^8\textrm{He}$ inelastic scattering to ${}^8\textrm{He}(2^+_1)$, the MCC+AMD calculation overshot the $(p,p')$ cross sections at $E=72$ MeV/A by a factor of three. According to a phenomenological model analysis, $M_n$ values in the range of 4--6 fm$^2$ were favored to reproduce the ${}^8\textrm{He}(2^+_1)$ cross sections of the $p+{}^8\textrm{He}$ reaction at $E=72$ MeV/A. For the $α+{}^8\textrm{He}$ reaction, the MCC+AMD calculation reproduced the elastic cross sections at $E=26$ MeV/A. Theoretical predictions of the ($p,p'$) and ($α,α'$) cross sections to the ${}^8\textrm{He}(0^+_2)$, ${}^8\textrm{He}(1^-_1)$, ${}^8\textrm{He}(2^+_3)$ and ${}^8\textrm{He}(3^-_1)$ states are also given.

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arXiv2020

Neutron dominance in excited states of $^{26}$Mg and $^{10}$Be probed by proton and alpha inelastic scattering

Isospin characters of nuclear excitations in $^{26}$Mg and $^{10}$Be are investigated via proton($p$) and alpha($α$) inelastic scattering. A structure model of antisymmetrized molecular dynamics (AMD) is applied to calculate the ground and excited states of $^{26}$Mg and $^{10}$Be. The calculation describes the isoscalar feature of the ground-band $2^+_1$($K^π=0^+_1$) excitation and predicts the neutron dominance of the side-band $2^+_2$($K^π=2^+$) excitation in $^{26}$Mg and $^{10}$Be. The $p$ and $α$ inelastic scattering off $^{26}$Mg and $^{10}$Be is calculated by microscopic coupled-channel (MCC) calculations with a $g$-matrix folding approach by using the matter and transition densities of the target nuclei calculated with AMD. The calculation reasonably reproduces the observed $0^+_1$, $2^+_1$, and $2^+_2$ cross sections of $^{26}$Mg+$p$ scattering at incident energies $E_p=$24 and 40 MeV and of $^{26}$Mg+$α$ scattering at $E_α=$104 and 120 MeV. For $^{10}$Be+$p$ and $^{10}$Be+$α$ scattering, inelastic cross sections to the excited states in the $K^π=0^+_1$ ground-, $K^π=2^+$ side-, $K^π=0^+_2$ cluster-, and $K^π=1^-$ cluster-bands are investigated. The isospin characters of excitations are investigated via inelastic scattering processes by comparison of the production rates in the $^{10}$Be+$p$, $^{10}$Be+$α$, and $^{10}$C+$p$ reactions. The result predicts that the $2^+_2$ state is selectively produced by the $^{10}$Be+$p$ reaction because of the neutron dominance in the $2^+_2$ excitation as in the case of the $^{26}$Mg+$p$ scattering to the $2^+_2$ state, whereas its production is significantly suppressed in the $^{10}$C+$p$ reaction.

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arXiv2020

Properties of $K^π=0^+_1$, $K^π=2^-$, and $K^π=0^-_1$ bands of $^{20}$Ne probed via proton and alpha inelastic scattering

The $K^π=0^+_1$, $K^π=2^-$, and $K^π=0^-_1$ bands of $^{20}$Ne are investigated with microscopic structure and reaction calculations via proton and $α$ inelastic scattering off $^{20}$Ne. Structures of $^{20}$Ne are calculated with variation after parity and total angular momentum projections in the antisymmetrized molecular dynamics(AMD). The $K^π=0^+_1$ and $K^π=0^-_1$ bands have $^{16}\textrm{O}+α$ cluster structures, whereas the $K^π=2^-$ band shows a $^{12}\textrm{C}+2α$-like structure. Microscopic coupled-channel calculations of proton and $α$ scattering off $^{20}$Ne are performed by using the proton-nucleus and $α$-nucleus potentials, which are derived by folding the Melbourne $g$-matrix $NN$ interaction with AMD densities of $^{20}$Ne. The calculation reasonably reproduces the observed cross sections of proton scattering at $E_p=25$--35 MeV and $α$ scattering at $E_α=104$--386 MeV. Transition properties from the ground to excited states are discussed by reaction analyses of proton and $α$ inelastic processes. Mixing of the $K^π=2^-$ and $K^π=0^-_1$ bands is discussed by detailed analysis of the $0^+_1\to 3^-_1$ and $0^+_1\to 3^-_2$ transitions. For the $3^-_1$ state, mixing of the $K^π=0^-_1$ cluster component in the $K^π=2^-$ band plays an important role in the transition properties.

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arXiv2020

Variation after $K$-projection in antisymmetrized molecular dynamics for low-energy dipole excitations in $^{10}$Be and $^{16}$O

For study of dipole excitations, a new method of variation after $K$-projection in the framework of antisymmetrized molecular dynamics (AMD) with the deformation $β$ constraint was proposed. The method was applied to $^{10}$Be and $^{16}$O to describe low-energy dipole excitations and found to be a useful and economical approach for dipole excitations. In the application to $^{10}$Be, two dipole states in low-energy region were described. For $^{16}$O, the $1_1^-$ and $1_2^-$ states with remarkable dipole strengths were obtained. The $1_1^-$ state is characterized by significant toroidal dipole (TD) and compressional dipole strengths, whereas the $1_2^-$ has significant TD strength and shows a developed $α+ {}^{16}$O cluster structure. Dipole properties in $^{16}$O were discussed by analysis of current densities of the dipole transitions.

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arXiv2020

Transition properties of low-lying states in $^{28}$Si probed via inelastic proton and alpha scattering

$0^+$, $1^-$, $2^+$, and $3^-$ excitations of $^{28}\textrm{Si}$ are investigated via proton and $α$ inelastic scattering off $^{28}\textrm{Si}$. The structure calculation of $^{28}\textrm{Si}$ is performed with the energy variation after total angular momentum and parity projections in the framework of antisymmetrized molecular dynamics (AMD). As a result of the AMD calculation, the oblate ground and prolate bands, $0^+$ and $3^-$ excitations, and the $1^-$ and $3^-$ states of the $K^π=0^-$ band are obtained. Using the matter and transition densities of $^{28}\textrm{Si}$ obtained by AMD, microscopic coupled-channel calculations of proton and $α$ scattering off $^{28}\textrm{Si}$ are performed. The proton-$^{28}\textrm{Si}$ potentials in the reaction calculation are microscopically derived by folding the Melbourne $g$-matrix $NN$ interaction with the AMD densities of $^{28}\textrm{Si}$. The $α$-$^{28}\textrm{Si}$ potentials are obtained by folding the nucleon-$^{28}\textrm{Si}$ potentials with an $α$ density. The calculation reasonably reproduces the observed elastic and inelastic cross sections of proton and $α$ scattering. Transition properties are discussed by combining the reaction analysis of proton and $α$ scattering and structure features such as transition strengths and form factors. The isoscalar monopole and dipole transitions are focused.

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arXiv2019

Cluster correlation and nuclear vorticity in low-lying $1^-$ states of $^{24}$Mg

We investigated cluster correlation and nuclear voricity in low-lying $1^-$ states of $^{24}$Mg within antisymmetrized molecular dynamics framework. We found that the toroidal and compressional dipole modes separately appear as the $K=1$ and $K=0$ states. The $1^-$ ($K=1$) state is the toroidal dipole state with the strong nuclear vorticity but no prominent cluster structure, and the $1^-$ ($K=0$) state is the compressional dipole state having enhanced cluster structure but has the weaker vorticity.

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arXiv2019

Quantitative description of the $^{20}$Ne($p$,$pα$)$^{16}$O cross section as a means of probing the surface $α$ amplitude

The proton-induced $α$ knockout reaction has been utilized for decades to investigate the $α$ cluster states of nuclei, of the ground state in particular. However, even in recent years, it is reported that the deduced $α$ spectroscopic factors from $α$ knockout experiments and reaction analyses with a phenomenological $α$ cluster wave function diverge depending on the kinematical condition of the reaction. In the present study we examine the theoretical description of the $^{20}$Ne($p$,$pα$)$^{16}$O cross section based on the antisymmetrized molecular dynamics and the distorted wave impulse approximation by comparing with existing experimental data. We also investigate the correspondence between the $α$ cluster wave function and the $α$ knockout cross section. The existing $^{20}$Ne($p$,$pα$)$^{16}$O data at 101.5 MeV is well reproduced by the present framework. Due to the peripherality of the reaction, the surface region of the cluster wave function is selectively reflected to the knockout cross section. A quantitatively reliable $α$ cluster wave function, $p$-$α$ cross section, and distorting potentials between scattering particles, $α$-$^{16}$O in particular, are crucial for the quantitative description of the ($p$,$pα$) cross section. Due to the peripherality of the reaction, the ($p$,$pα$) cross section is a good probe for the surface $α$ amplitude.

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arXiv2019

Lattice QCD study of static quark and antiquark correlations via entanglement entropies

We study the color correlation between static quark and antiquark ($q\bar q$) in the confined phase via reduced density matrices $ρ$ defined in color space. We adopt the standard Wilson gauge action and perform quenched calculations with the Coulomb gauge condition for reduced density matrices. The spatial volumes are $L^3 = 8^3$, $16^3$, $32^3$ and $48^3$, with the gauge couplings $β= 5.7$, 5.8 and 6.0. Each element of the reduced density matrix in the sub space of quarks' color degrees of freedom of the $q\bar q$ pair is calculated from staples defined by link variables. As a result, we find that $ρ$ is well written by a linear combination of the strongly correlated $q\bar q$ pair state with the color-singlet component and the uncorrelated $q\bar q$ pair state with random color configurations. We compute the Renyi entropies $S^{\rm Renyi}$ from $ρ$ to investigate the $q\bar q$ distance dependence of the color correlation of the $q\bar q$ pair and find that the color correlation is quenched as the distance increases.

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arXiv2019

Cluster structures and monopole transitions of $^{14}$C

Cluster structures of $^{14}$C were investigated with a method of antisymmetrized molecular dynamics (AMD) combined with a $3α+nn$ cluster model while focusing on the monopole excitations and linear-chain $3α$ band. Variation after parity and angular momentum projections was performed in the AMD framework, and the generator coordinate method was applied to take into account various $3α+nn$ cluster configurations. Energy spectra and monopole and $E2$ transition strengths of $0^+$, $2^+$, and $4^+$ states were calculated to assign band structures. The $0^+_3$ state with remarkable monopole transition was obtained as a vibrational mode of the triangle $3α$ configuration. In addition, the linear-chain $3α$ band from the band-head $0^+_4$ state was obtained. $^{10}$Be$+α$ decay widths of $0^+$, $2^+$, and $4^+$ states were evaluated. $α$ inelastic scattering off $^{14}$C was also investigated by the microscopic coupled-channel calculation with the $g$-matrix folding model to propose possible observation of the $0^+_3$ state via $α$ scattering experiments.

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arXiv2019

Microscopic calculation of inelastic proton scattering off $^{18}$O, $^{10}$Be, $^{12}$Be, and $^{16}$C for study of neutron excitation in neutron-rich nuclei

The microscopic coupled-channel calculation of inelastic proton scattering is performed for the study of neutron excitations in $2^+_1$ states of $^{18}$O, $^{10}$Be, $^{12}$Be, and $^{16}$C. Proton-nucleus potentials in the coupled-channel calculation are microscopically derived by folding the Melbourne $g$-matrix $NN$ interaction with matter and transition densities of target nuclei obtained by the structure model calculation of antisymmetrized molecular dynamics. The calculated result reasonably reproduces the elastic and inelastic proton scattering cross sections, and supports the dominant contribution of neutron in the $2^+_1$ excitation of $^{12}$Be and $^{16}$C as well as $^{18}$O. Sensitivity of the inelastic scattering cross sections to the neutron transition density is discussed. The exotic feature of the neutron transition density with the amplitude in the outer region in $^{12}$Be and $^{16}$C is focused.

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arXiv2019

Direct probing of the cluster structure in ${}^{12}$Be via $α$-knockout reaction

Background: Recent theoretical and experimental researches using proton-induced $α$-knockout reactions provide direct manifestation of $α$-cluster formation in nuclei. In recent and future experiments, $α$-knockout data are available for neutron-rich beryllium isotopes. In $^{12}$Be , rich phenomena are induced by the formation of $α$-clusters surrounded by neutrons, for instance, breaking of the neutron magic number $N=8$. Purpose: Our objective is to provide direct probing of the $α$-cluster formation in the $^{12}$Be target through associating the structure information obtained by a microscopic theory with the experimental observables of $α$-knockout reactions. Method: We formulate a new wave function of the Tohsaki-Horiuchi-Schuck-R{ö}pke (THSR) type for the structure calculation of ${}^{12}$Be nucleus and integrate it with the distorted wave impulse approximation framework for the $α$-knockout reaction calculation of $^{12}$Be$(p,pα)^{8}$He. Results: We reproduce the low-lying spectrum of the $^{12}$Be nucleus using the THSR wave function and discuss the cluster structure of the ground state. Based on the microscopic wave function, the optical potentials and $α$-cluster wave function are determined and utilized in the calculation of ${}^{12}$Be($p,pα$)${}^{8}$He reaction at 250 MeV. The possibility of probing the clustering state of $^{12}$Be through this reaction is demonstrated by analysis of the triple differential cross sections that are sensitively dependent on the $α$-cluster amplitude at the nuclear surface. Conclusions: This study provides a feasible approach to validate directly the theoretical predictions of clustering features in the $^{12}$Be nucleus through the $α$-knockout reaction.

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arXiv2019

Investigation of spatial manifestation of $α$ clusters in $^{16}$O via $α$-transfer reactions

Recently, we have determined surface distributions of $α$ clusters in the ground state of $^{20}\mathrm{Ne}$ from $α$-transfer cross sections, without investigating the properties of its excited states. In this paper we extend our comprehension of $α$-cluster structures in excited states of nuclei through reaction studies. In particular we focus on $^{16}\mathrm{O}$, for which attention has been paid to advances of structure theory and assignment regarding $4^+$-resonance states. We study the surface manifestation of the $α$-cluster states in both the ground and excited states of $^{16}\mathrm{O}$ from the analysis of the $α$-transfer reaction $^{12}\mathrm{C}(^6\mathrm{Li},d)^{16}\mathrm{O}$. The $α$-transfer reaction is described by the distorted-wave Born approximation. We test two microscopic wave functions as an input of reaction calculations. Then a phenomenological potential model is introduced to clarify the correspondence between cluster-wave functions and transfer-cross sections. Surface peaks of the $α$-wave function of $^{16}\mathrm{O}(0^+)$ are sensitively probed by transfer-cross sections at forward angles, while it remains unclear how we trace the surface behavior of $^{16}\mathrm{O}(4^+)$ from the cross sections. We are able to specify that the $α$-cluster structure in the $0_1^+$ and $0_2^+$ states prominently manifests itself at the radii $\sim 4$ and $\sim 4.5$~fm, respectively. It is remarkable that the $4_1^+$ state has the $^{12}\mathrm{C}+α$-cluster component with the surface peak at the radius $\sim 4$ or outer, whereas the $^{12}\mathrm{C}+α$-cluster component in the $4_2^+$ state is found not to be dominant. The $4_2^+$ state is difficult to be interpreted by a simple potential model assuming the $^{12}\mathrm{C}+α$ configuration only.

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arXiv2019

First microscopic coupled-channel calculation of $α$ inelastic cross sections on $^{16}$O

The $α$ inelastic scattering on $^{16}$O is investigated with the coupled-channel calculation using the $α$-nucleus coupled-channel potentials, which are microscopically derived by folding the the Melbourne $g$-matrix $NN$ interaction with the $^{16}$O and $α$ densities. The matter and transition densities of $^{16}$O are calculated by a microscopic structure model of the variation after the spin-parity projections combined with the generator coordinate method of $^{12}$C+$α$ in the framework of the antisymmetrized molecular dynamics. The calculation reproduces the observed elastic and inelastic cross sections at incident energies of $E_α$=104 MeV, 130 MeV, 146 MeV, and 386 MeV. The coupled-channel effect on the cross sections is also discussed.

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arXiv2019

$α$ scattering cross sections on $^{12}$C with microscopic coupled-channel calculation

$α$ elastic and inelastic scattering on $^{12}$C is investigated with the coupled-channel calculation using microscopic $α$-$^{12}$C potentials, which are derived by folding the Melbourne $g$-matrix $NN$ interaction with the matter and transition densities of $^{12}$C. These densities are obtained by a microscopic structure model of the antisymmetrized molecular dynamics combined with and without the $3α$ generator coordinate method. The calculation reproduces satisfactorily well the observed elastic and inelastic cross sections at incident energies of $E_α=130$~MeV, 172.5~MeV, 240~MeV, and 386~MeV with no adjustable parameter. Isoscalar monopole and dipole excitations to the $0^+_2$, $0^+_3$, and $1^-_1$ states in the $α$ scattering are discussed.

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arXiv2019

Isoscalar dipole excitations in $^{16}$O

Isoscalar (IS) monopole and dipole excitations in $^{16}$O were investigated by the method of shifted basis antisymmetrized molecular dynamics combined with the generator coordinate method. Significant strengths of the IS monopole and dipole transitions were obtained in the low-energy region below the giant resonances. In addition to the compressive mode, which mainly contributes to the high-energy strengths for the IS dipole giant resonance, we obtained a variety of low-energy dipole modes such as the vortical dipole mode in the $1^-_1$ state of the vibrating tetrahedral $4α$ and the $^{12}$C+$α$ cluster structure in the $1^-_2$ state. The $1^-_1$ state contributes to the significant low-energy strength of the IS dipole transition as 5\% of the energy-weighted sum rule, which describes well the experimental data observed by the $α$ inelastic scattering.

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arXiv2019

Low-energy dipole excitation modes in ${}^{10}$Be

Low-energy dipole excitations in ${}^{10}$Be were investigated based on the generator coordinate method with $α+ {}^6$He and $α+ α+ 2n$ cluster models. We obtained three $1^-$ states in $E_{x} < 15$~MeV, which show different characters in the $E1$, compressive dipole, and toroidal dipole transition strengths. We found the strong toroidal dipole transition in the $1_1^-$ state, remarkable $E1$ strength in the $1^-_2$ state, and the strong $E1$ and compressive dipole strength in the $1^-_3$ state. The $1^-_1$ is described by the $α+ {}^6$He cluster structure, where as the $1^-_2$ and $1^-_3$ states are understood by three-body excitations of the $α+ α+ 2n$ clustering.

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