arXiv subjects

Yoshiko Kanada-En'yo

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

At least 19 recordsLinked to original sources

arXiv2026

3-body cluster gas structures in the excited $0^+$ states of $N=6$ nuclei

We investigate the cluster structure of $α+{}^2n+{}^2n$ in $^8\mathrm{He}(0_2^+)$ and compare it with those of $2α+{}^2n$ in $^{10}\mathrm{Be}(0_2^+)$ and $3α$ in $^{12}\mathrm{C}(0_2^+)$ to understand the emergence mechanism of the 3-body cluster gas states. We apply an extended cluster model combined with cluster breaking components in a microscopic framework using effective nuclear forces based on nucleon degrees of freedom including the antisymmetrization between nucleons. In detailed analysis of the 3-body cluster structures of excited $0^+$ states, it is shown that $^8\mathrm{He}(0_2^+)$ exhibits 3-body cluster gas feature of $α+{}^2n+{}^2n$ similar to $^{12}\mathrm{C}$ but contains significant mixing of a 2-body-like $(α+{}^2n)+{}^2n$ component. We discuss cluster structures of $^8\mathrm{He}(0_2^+)$ and $^{12}\mathrm{C}(0_2^+)$ from the point of view of inter-cluster energies of ${}^2n \text{-} {}^2n$ and $α\text{-}{}^2n$ in comparison with the $α\text{-} α$ energies and find that the origin for the 2-body-like $(α+{}^2n)+{}^2n$ mixing is the unbalance of the $α\text{-}{}^2n$ and ${}^2n \text{-} {}^2n$ energies, in which Pauli effects play an essential role through the kinetic energy loss and internal potential energy loss of clusters. We clarify the emergence mechanism of the 3-body cluster gas state in excited $0^+$ states of $^8\mathrm{He}$ and $^{12}\mathrm{C}$ systems. The balance of inter-cluster interactions is essential for the appearance of 3-body cluster gas states. Microscopic effects, i.e., the Pauli effects of nucleons between clusters play a crucial role in cluster structures of excited $0^+$ states.

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arXiv2026

Lattice QCD study of color correlations between quarks in static multiquark systems

We study the color correlation between two static quarks in 3Q ($QQQ$) and 4Q ($QQ\bar Q\bar Q$) multiquark systems at $T=0$ based on the reduced two-body density matrices $ρ$ in color space. We perform quenched lattice QCD calculations with the Coulomb gauge adopting the standard Wilson gauge action, and the spatial volume is $L^3 = 32^3$ at $β= 5.8$, which corresponds to the lattice spacing $a=0.14$ fm and the system volume $L^3=4.5^3$ fm$^3$. We evaluate the two-body color density matrix $ρ$ of static quarks, and investigate the dependence of color correlations on the quarks' spatial configuration. As a result, we find that the color correlations depend on the minimal path length along a flux tube which connects two quarks under consideration. The color correlation between quarks quenches because of color leak into the gluon field (flux tube) and finally approaches the random color configuration in the large distance limit. We also find a ``universality'' in the flux-tube path length dependence of the color correlation for 2Q, 3Q, and 4Q ground-state systems. Our results show that the color correlations of end-point quarks can be a clue to clarify the internal structures of hadrons, including exotic (multiquark) hadrons.

hep-lat↗

arXiv2025

$α+{}^2n+{}^2n$ 3-body cluster structures and dineutron breaking in ${}^8 \mathrm{He}$

The $0_2^+$ state of ${}^8\mathrm{He}$ has been discovered by a recent experiment, which suggested a developed cluster structure of spatially correlated neutron pairs, called "dineutrons" (${}^2n$). We aim to investigate the structure of ${}^8\mathrm{He}(0^+_1)$ and ${}^8\mathrm{He}(0^+_2)$ to clarify the monopole excitation mode in ${}^8\mathrm{He}$ system while focusing on the $α+{}^2n+{}^2n$ cluster structures and the breaking of ${}^2n$ clusters. We apply a microscopic cluster model with the generator coordinate method for the $α+{}^2n+{}^2n$ cluster and ${}^6\mathrm{He}+{}^2n$ cluster dynamics. The $p_{3/2}$-closure component, which is induced by the spin-orbit force, is also incorporated. The present calculation reasonably reproduces the experimental data of the properties of ${}^8\mathrm{He}$, such as $2n$ and $4n$ separation energies, energy spectra, and radii. The spatially developed cluster structure of the $0_2^+$ state is obtained. The $0_1^+$ and $0_2^+$ states have dominant components of $α+{}^2n+{}^2n$ 3-body cluster, but contain significant ${}^2n$ breaking components which contribute to the energy gain and size shrinking of the ${}^8\mathrm{He}$ system. The monopole excitation in ${}^8\mathrm{He}$ is regarded as a radial excitation, which is similar to that in ${}^{12}\mathrm{C}$. The $α+{}^2n+{}^2n$ cluster structures play a dominant role in ${}^8\mathrm{He}(0_{1,2}^+)$, and the mixing of the dineutron breaking contributes to significant structural effects.

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arXiv2024

Lattice QCD study of color correlations between static quarks with gluonic excitations

We study the color correlation between static quark and antiquark ($q\bar q$) that is accompanied by gluonic excitations in the confined phase at $T=0$ by constructing reduced density matrices $ρ$ in color space. We perform quenched lattice QCD calculations with the Coulomb gauge adopting the standard Wilson gauge action, and the spatial volume is $L^3 = 32^3$ at $β= 5.8$, which corresponds to the lattice spacing $a=0.14$ fm and the system volume $L^3=4.5^3$ fm$^3$. We evaluate the color density matrix $ρ$ of static $q\bar q$ pairs in 6 channels (${Σ_g^+}$, ${{Σ_g^+}'}$, ${Π_u}$, ${Π_u'}$, ${Δ_g}$, ${Δ_g'}$), and investigate the interquark-distance dependence of color correlations. We find that as the interquark distance increases, the color correlation quenches because of color leak into the gluon field and finally approaches the random color configuration in the $q\bar q$ systems with and without gluonic excitations. For this color screening effect, we evaluate the "screening mass" to discuss its dependence on channels, the quantum number of the gluonic excitations.

hep-lat↗

arXiv2024

QCD sum rules for positive and negative parity heavy baryons at next-to-leading order in $α_s$-expansion

QCD sum rules for positive and negative parity heavy baryons in the heavy quark limit are formulated. We apply the method to $Λ$ and $Σ$ channels. We include the next-to-leading order corrections in $α_s$-expansion to dimension 0 and 3 terms in the operator product expansion. The corrections lead to the considerable reduction of the predicted masses and significantly improves the stability with respect to the Borel parameter, especially for negative parity states. It is also found that in the heavy quark limit chiral odd condensates do not contribute to the negative parity states.

hep-ph↗

arXiv2022

Effects of density-dependent spin-orbit interactions in Skyrme-Hartree-Fock-Bogoliubov calculations of the charge radii and densities of Pb isotopes

I have investigated the $N$-dependence of the charge radii $r_c$ across $N=126$ in the Pb isotopes and the surface densities of $^{208}$Pb using new Skyrme interactions that contain a density-dependent spin-orbit term, which I have named the Skyrme-ddso interactions. I have compared the results obtained using Skyrme-Hartree-Fock-Bogoliubov calculations that employ the Skyrme-ddso interactions with the original Skyrme results and have discussed the effects of including the density-dependent spin-orbit term. The results for the kink behavior of $r_c$ at $N=126$ in the Pb isotopes were improved by the inclusion of the density-dependent spin--orbit term. Moreover, the new Skyrme calculations yield better results for the inner part of the surface proton density of $^{208}$Pb at $r\sim 5$ fm. The change in the $\ell s$ potentials from the original Skyrme calculation contributes to the kink behavior through its effects on the $\ell s$ splitting of the neutron $2g_{7/2,9/2}$ orbitals. It also affects the inner part of the surface proton density through its effect on the proton $1h_{11/2}$ orbitals. I have further demonstrated that the change in the isoscalar-to-isovector ratio of the spin--orbit term makes only a minor contribution to the single-particle energies and to the kink behavior in the Pb isotopes. In addition, I have investigated $^{48}$Ca using Skyrme-Hartree-Fock calculations with the new Skyrme interactions and have determined the effects of the density-dependent spin--orbit term on its radii and densities.

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arXiv2022

Deformation effects on the surface neutron densities of stable S and Ni isotopes probed by proton elastic scattering via isotopic analysis

To extract structure information from proton elastic scattering off S isotopes at 320 MeV and Ni isotopes at $E_p=180$ MeV, this study proposes isotopic analyses combining nuclear structure and reaction calculations. The isotonic analysis was repeated on $^{48}$Ca and $^{50}$Ti. The structure calculations were performed by using the spherical and deformed Relativistic Hartree--Bogoliubov (RHB) calculations, and the spherical nonrelativistic Skyrme Hartree--Fock--Bogoliubov calculations. The $(p,p)$ reactions were calculated using the relativistic impulse approximation (RIA) assuming the theoretical densities of target nuclei. The RIA calculations using the target densities obtained by the RHB calculation, along with the density-dependent point-coupling interactions reasonably reproduced the $(p,p)$ cross sections in the studied mass number region. The nuclear structure and $(p,p)$ reactions were analyzed in detail; especially, the effects of deformation on the isotopic systematics of the surface densities and $(p,p)$ cross sections were clarified. The deformation effects were found to be essential to describe the isotopic systematics of the experimental $(p,p)$ cross sections. Overall, isotopic and isotonic analyses are useful for extracting the nuclear structure information such as nuclear deformations and single-particle features from proton scattering, enabling sensitive probing of surface densities.

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arXiv2022

Neutron $3s_{1/2}$ occupation change across the stable tin isotopes investigated using isotopic analysis of proton scattering at 295 MeV

The isotopic systematics of Sn isotopes in the range A=116--124 were investigated by combining the nuclear structure and reaction calculations for the analysis of Sn(p,p) reactions at 295 MeV. The Sn(p,p) reactions were calculated employing relativistic impulse approximation (RIA) with theoretical densities obtained for the Sn isotopes from relativistic Hartree-Bogoliubov (RHB) calculations with the DD-ME2 interaction and nonrelativistic Skyrme Hartree-Fock-Bogoliubov (SHFB) calculations with the SKM* interaction. Calculation using the DD-ME2 density reproduced the experimental data for $^{122}$Sn(p,p) but overestimated the $^{116}$Sn(p,p) and $^{118}$Sn(p,p) cross sections at backward angles. In the isotopic analysis of the cross section ratio $R(σ)$ of $^{122}$Sn to $^{116}$Sn, a calculation using the SKM* density reproduced the peak amplitudes of $R(σ)$ obtained from the experimental cross sections, whereas a calculation using the DD-ME2 density did not. The ratio $R(σ)$ was found to be sensitive to the isotopic change of the neutron $3s_{1/2}$ occupation through the isotopic difference of the surface neutron density around r=4--5 fm. Isotopic analysis indicated that a rapid increase of the $3s_{1/2}$ occupation from $^{116}$Sn to $^{122}$Sn obtained by the DD-ME2 calculation is unlikely. This result derived from the 295 MeV Sn(p,p) cross section data is consistent with the direct measurement of the neutron occupations in Sn isotopes by neutron transfer and pick-up reactions.

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arXiv2022

Collective model for cluster motion in $^8$Be, $^{12}$C, and $^{16}$O systems

A microscopic $nα$ cluster model was applied to $^{8}$Be, $^{12}$C, and $^{16}$O systems to investigate cluster motion in the ground state and radial excitation. In the microscopic calculation of $^{12}$C and $^{16}$O using the generator coordinate method with the coordinate $D$ of the $α$-$α$ distance, excited states were obtained as the large-amplitude mode built on the ground state. A collective model was constructed to describe the cluster motion of these states by utilizing inputs from the microscopic cluster model such as the norm kernel and energy expectation values. Furthermore, the cluster model was extended by introducing the imaginary part of the coordinate $D$ to incorporate the dynamical effects on the collective mass. The collective wave function obtained with the collective model was found to be in reasonable agreement with the results of the generator coordinate method for energies, root-mean-square radii, and amplitude functions.

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arXiv2021

Investigation of multi-step effects for proton inelastic scattering to the $2^{+}_{1}$ state in $^6$He

Multi-step effects between bound, resonant, and non-resonant states have been investigated by the continuum-discretized coupled-channels method (CDCC). In the CDCC, a resonant state is treated as multiple states fragmented in a resonance energy region, although it is described as a single state in usual coupled-channel calculations. For such the fragmented resonant states, one-step and multi-step contributions to the cross sections should be carefully discussed because the cross sections obtained by the one-step calculation depend on the number of those states, which corresponds to the size of the model space. To clarify the role of the multi-step effects, we propose the one-step calculation without model-space dependence for the fragmented resonant states. Furthermore, we also discuss the multi-step effects between the ground, $2^{+}_{1}$ resonant, and non-resonant states in $^6$He for proton inelastic scattering.

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arXiv2021

Shell effect in $A=$116--124 Tin isotopes investigated using isotopic analysis of proton scattering at 295 MeV

Proton elastic scattering off Sn isotopes at $E_p=295$ MeV in the mass number range of $A=$116--124 was investigated using calculation employing relativistic impulse approximation (RIA) with theoretical densities obtained for the Sn isotopes from relativistic Hartree-Bogoliubov (RHB) and nonrelativistic Skyrme Hartree-Fock-Bogoliubov (SHFB) calculations of spherical nuclei. In the RIA calculations, a modified version of the Murdock and Horowitz model that includes a density dependence in the effective nucleon-nucleon ($NN$) interaction was used. A calculation using the theoretical density obtained from a relativistic calculation employing the DD-ME2 interaction successfully reproduced the experimental data for $^{122}$Sn$(p,p)$, but it overestimated the $^{116}$Sn$(p,p)$ and $^{118}$Sn$(p,p)$ cross sections at backward angles. Isotopic analyses of the $(p,p)$ reactions combined with nuclear structure properties were performed based on reaction calculations that used a model density modified from the DD-ME2 density to optimize the neutron density of the Sn isotopes by fitting the isotopic cross section ratios. The resulting optimized density reproduced the experimental $(p,p)$ data for the series of Sn isotopes from $^{116}$Sn to $^{124}$Sn. The neutron root-mean-square(rms) radii and the skin thickness of the Sn isotopes obtained in the present analysis exhibited smooth $A$ dependences in the range of $A=$116--124, which are consistent with the theoretical predictions obtained using the DD-ME2 interaction but seem to contradict the experimental results determined from the $(p,p)$ data. In a detailed analysis of the surface neutron density probed by proton elastic scattering, a signal of the shell effect at $N=66$ in Sn isotopes was found.

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arXiv2021

Isotopic analysis of 295 MeV proton scattering off $^{204,206,208}$Pb for improvement of neutron densities and radii

A new method of reaction analysis for proton elastic scattering is proposed, combining systematic analyses of nuclear structure and reactions in a series of isotopes. This method is applied to $^{204}$Pb$(p,p)$, $^{206}$Pb$(p,p)$, and $^{208}$Pb$(p,p)$ at $E_p=295$ MeV to obtain improved neutron densities and radii from experimental cross section data. The reaction calculation is performed according to the relativistic impulse approximation using the modified Murdock and Horowitz model with density-dependent effective $NN$ interaction. Analysis of Pb isotopes is performed using theoretical densities given by the relativistic Hartree-Bogoliubov and nonrelativistic Skyrme Hartree-Fock-Bogoliubov calculations and the experimental density extracted from the $(p,p)$ data at 295 MeV. The isotopic ratios ($R(σ)$) of the $^{A}$Pb$(p,p)$-to-$^{206}$Pb$(p,p)$ cross sections are analyzed in connection with the isotopic differences ($D(ρ_n)$ and $D(r_n)$) in neutron densities $(ρ_n(r))$ and radii $(r_n)$ between $^A$Pb and $^{208}$Pb. A hole-model analysis is performed, assuming $^{204}$Pb and $^{206}$Pb as a $^{208}$Pb core and neutron holes to clarify the one-to-one correspondence between isotopic structure properties such as $D(ρ_n)$ and $D(r_n)$ and the isotopic cross-section ratio. By fitting $R(σ)$, the values of $D(ρ_n)$ and $D(r_n)$ are extracted from the experimental $(p,p)$ cross section data with less uncertainty of the structure and reaction models. The isotopic neutron radius difference between $^{206}$Pb and $^{208}$Pb was obtained as $D(r_n)=-0.012$ fm with an acceptable range of $D(r_n)=-0.03 \sim -0.006$ fm.

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arXiv2021

Low-energy dipole excitations in $^{20}$O with antisymmetrized molecular dynamics

Low-energy dipole (LED) excitations in $^{20}$O were investigated by variation after $K$-projection of deformation($β$)-constraint antisymmetrized molecular dynamics combined with the generator coordinate method. We obtained two LED states, namely, the $1_1^-$ state with one-proton excitation on the relatively weak deformation and the $1_2^-$ state with a parity asymmetric structure of the normal deformation. The former is characterized by a toroidal dipole (TD) mode with vortical nuclear current, whereas the latter is associated with a low-energy $E1$ mode caused by surface neutron oscillation along the prolate deformation. The TD (vortical) and $E1$ modes separately appear as the $K^π=1^-$ and $K^π=0^-$ components of the deformed states, respectively, but couple with each other in the $1_1^-$ and $1_2^-$ states of $^{20}$O because of $K$-mixing, and shape fluctuation. As a result of the mixing, TD and $E1$ transition strengths are fragmented into the $1_1^-$ and $1_2^-$ states. We also obtained the $K^π=0^+$, $K^π=0^-$, and $K^π=1^-$ bands with cluster structures in the energy region higher than the LED states.

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arXiv2021

Lattice QCD study of static quark and antiquark correlations at finite $T$ via entanglement entropies

With the aim of clarification of color correlations among quarks, we investigate the color correlation between a static quark and an antiquark (static $q\bar q$) below and above the phase transition temperature $T_c$ through the entanglement entropy(EE). By a quenched lattice QCD calculation on an anisotropic lattice adopting the standard Wilson gauge action in the Coulomb gauge, we compute a reduced density matrix $ρ$ defined in the color space, and the entanglement entropy $S_{\rm EE}$ constructed from $ρ$. The spatial volume is $L^3 = 24^3$ and the temporal extents are $N_T = 12,13,14,15,16,18,20$ and $24$, with a gauge coupling $β= 5.75$ and a renormalized anisotropy $ξ= 4.0$, which corresponds to temperatures between 180 and 370 MeV. From an analysis of $ρ$ and $S_{\rm EE}$, the color correlation between $q\bar q$ pairs is obtained as a function of the interquark distance $R$ and the temperature $T$. Below $T_c$, the $R$-dependence of the color correlation resembles that at $T=0$: the quark's color correlation gradually decreases as $R$ increases due to the color screening by in-between gluons. Above $T_c$, due to the deconfinement phase transition, the color correlation among quarks is found to quickly dissappear. Further, we investigate the color screening effect via the screening mass defined by $ρ$, and discuss the differences in the screening properties between the small and large R regions.

hep-lat↗

arXiv2021

Unexpectedly enhanced $α$-particle preformation in $^{48}$Ti probed by the $(p,pα)$ reaction

The formation of $α$ particle on nuclear surface has been a fundamental problem since the early age of nuclear physics. It strongly affects the $α$ decay lifetime of heavy and superheavy elements, level scheme of light nuclei, and the synthesis of the elements in stars. However, the $α$-particle formation in medium-mass nuclei has been poorly known despite its importance. Here, based on the $^{48}{\rm Ti}(p,pα)^{44}{\rm Ca}$ reaction analysis, we report that the $α$-particle formation in a medium-mass nucleus $^{48}{\rm Ti}$ is much stronger than that expected from a mean-field approximation, and the estimated average distance between $α$ particle and the residue is as large as 4.5 fm. This new result poses a challenge of describing four nucleon correlations by microscopic nuclear models.

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arXiv2020

Low-energy dipole excitation mode in $^{18}$O with antisymmetrized molecular dynamics

Low-energy dipole (LED) excitations in $^{18}$O were investigated using a combination of the variation after $K$-projection in the framework of antisymmetrized molecular dynamics with $β$-constraint with the generator coordinate method. We obtained two LED states, namely, the $1_1^-$ state with a dominant shell-model structure and the $1_2^-$ state with a large $^{14}\textrm{C}+α$ cluster component. Both these states had significant toroidal dipole (TD) and compressive dipole (CD) strengths, indicating that the TD and CD modes are not separated but mixed in the LED excitations of $^{18}$O. This is unlike the CD and TD modes for well-deformed nuclei such as $^{10}$Be, where the CD and TD modes are generated as $K^π=0^-$ and $K^π=1^-$ excitations, respectively, in a largely deformed state.

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arXiv2020

Microscopic coupled-channel calculation of proton and alpha inelastic scattering to the $4^+_1$ and $4^+_2$ states of $^{24}$Mg

Background: The triaxial and hexadecapole deformations of the K=0+ and K=2+ bands of 24Mg have been investigated by the inelastic scatterings of various probes, including electrons, protons, and alpha particles, for a prolonged time. However, it has been challenging to explain the unique properties of the scatterings observed for the $4^+_1$ state through reaction calculations. Purpose: To investigate the structure and transition properties of the K=0+ and K=2+ bands of 24Mg employing the microscopic structure and reaction calculations via inelastic proton and alpha-scattering. Particularly, the E4 transitions to the $4^+_1$ and $4^+_2$ states were reexamined. Method: The structure of 24Mg was calculated employing the variation after the parity and total-angular momentum projections in the framework of the antisymmetrized molecular dynamics(AMD). The inelastic proton and alpha reactions were calculated by the microscopic coupled-channel (MCC) approach by folding the Melbourne g-matrix NN interaction with the AMD densities of 24Mg. Results: Reasonable results were obtained on the properties of the structure, including the energy spectra and E2 and E4 transitions of the K=0+ and K=2+ bands owing to the enhanced collectivity of triaxial deformation. The MCC+AMD calculation successfully reproduced the angular distributions of the $4^+_1$ and $4^+_2$ cross sections of proton scattering at incident energies of $E_p$=40--100MeV and alpha-scattering at $E_α$=100--400MeV. Conclusions: This is the first microscopic calculation that described the unique properties of the $0^+_1\to 4^+_1$ transition. In the inelastic scattering to the $4^+_1$ state, the dominant two-step process of the $0^+_1\to 2^+_1\to 4^+_1$ transitions and the deconstructive interference is the weak one-step process were essential.

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arXiv2020

Probing negative-parity states of $^{24}$Mg probed via proton and alpha inelastic scattering

[Background:] The band structure of the negative-parity states of $^{24}$Mg has not yet been clarified. The $K^π=0^-$, $K^π=1^-$, and $K^π=3^-$ bands have been suggested, but the assignments have been inconsistent between experiments and theories. [Purpose:] Negative-parity states of $^{24}$Mg are investigated by microscopic structure and reaction calculations via proton and alpha inelastic scattering to clarify the band assignment for the observed negative-parity spectra. [Method:] The structure of $^{24}$Mg was calculated using the antisymmetrized molecular dynamics~(AMD). Proton and alpha inelastic reactions were calculated using microscopic coupled-channel (MCC) calculations by folding the Melbourne $g$-matrix $NN$ interaction with the AMD densities of $^{24}$Mg. [Results:] The member states of the $K^π=0^+$, $K^π=2^+$, $K^π=0^-$, $K^π=1^-$, and $K^π=3^-$ bands of $^{24}$Mg were obtained through the AMD result. In the MCC+AMD results for proton and alpha elastic and inelastic cross sections, reasonable agreements were obtained with existing data, except in the case of the $4^+_1$ state. [Conclusions:] The $3^-$ state of the $K^π=3^-$ band and the $1^-$ and $3^-$ states of the $K^π=0^-$ bands were assigned to the $3^-_1$(7.62 MeV), $1^-_1$(7.56 MeV), and $3^-_2$(8.36 MeV) states, respectively. The present AMD calculation is the first microscopic structure calculation to reproduce the energy ordering of the $K^π=0^-$, $K^π=1^-$, and $K^π=3^-$ bands of $^{24}$Mg.

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