Publishing type：Research paper (scientific journal)  

DOI： 10.1103/physrevc.108.014614

Other URL： http://harvest.aps.org/v2/journals/articles/10.1103/PhysRevC.108.014614/fulltext

Authorship：Corresponding author   Publishing type：Research paper (scientific journal)  

DOI： 10.1103/physrevc.108.014322

Other URL： http://harvest.aps.org/v2/journals/articles/10.1103/PhysRevC.108.014322/fulltext

Authorship：Corresponding author   Publishing type：Research paper (scientific journal)  

DOI： 10.1103/physrevc.108.l011304

Other URL： http://harvest.aps.org/v2/journals/articles/10.1103/PhysRevC.108.L011304/fulltext

Publishing type：Research paper (scientific journal)  

Abstract

We present complete formulas of the allowed and first-forbidden transitions of nuclear beta decay taking into account the recoil-order and induced currents up to the next-to-leading order (NLO). The longitudinal part of the vector current is cleared away by the use of the conservation of the vector current for the multipole operators of the natural-parity transitions, which makes the effect of the meson exchange current for the vector current as small as possible. The formula is transparent enough to be applied to various beta-decay processes. As a numerical demonstration, we apply our formulas to the beta decay of a neutron-rich nucleus 160Sn. We find that the NLO corrections amount to 10–20 percent of the total decay rate, whereas the induced currents alter the rate at most by 5 percent.

DOI： 10.1093/ptep/ptad089

Other URL： https://academic.oup.com/ptep/article-pdf/2023/7/073D02/50967205/ptad089.pdf

Publishing type：Research paper (scientific journal)  

DOI： 10.1103/PhysRevC.107.L041304

Publishing type：Research paper (scientific journal)  

The properties of the deformed halo of Ne31 are discussed using the antisymmetrized molecular dynamics plus resonating group method (AMD+RGM). The AMD+RGM calculations describe a large neutron radius for the ground state and reveal that the ground state is dominated by core-excited components. The resonant states are also investigated by applying the analytical continuation of the coupling constant. It is found that the first excited state (the 5/2- state) is also dominated by core-excited components and has a small decay width, whereas the second excited state (the 7/2- state) is dominated by the valence neutron in the f wave coupled to the ground state of Ne30.

DOI： 10.1103/physrevc.107.024314

Other URL： http://harvest.aps.org/v2/journals/articles/10.1103/PhysRevC.107.024314/fulltext

Publishing type：Research paper (scientific journal)  

We investigate geometric configurations of α (4He nucleus) clusters in the second Jπ= 2 + state of 12C, which has been discussed as a rotational band member of the second 0 + state, the Hoyle state. The ground and excited 0 + and 2 + states are described by a three-α cluster model. The three-body Schrödinger equation with orthogonality conditions is accurately solved by the stochastic variational method with correlated Gaussian basis functions. To analyse the structure of these resonant states in a convenient form, we introduce a confining potential. The two-body density distributions together with the spectroscopic information clarify the structure of these states. We find that main configurations of both the second 0 + and 2 + states are acute-angled triangle shapes originating from the 8Be(0 +)+ α configuration. However, the 8Be + α components in the second 2 + state become approximately 2/3 because the 8Be subsystem is hard to excite, indicating that the state is not an ideal rigid rotational band member of the Hoyle state.

DOI： 10.1140/epja/s10050-023-00947-3

Other URL： https://link.springer.com/article/10.1140/epja/s10050-023-00947-3/fulltext.html

Authorship：Lead author,　Corresponding author   Publishing type：Research paper (scientific journal)  

The He4 nucleus is a well bound and highly correlated four-nucleon system that is also found in the form of α clusters as a substructure in nuclear many-body systems. The standard single-particle shell model cannot represent these four-body correlations. It is highly desirable to find a simple way to identify and distinguish these fundamental structures without large-scale computations. In this paper, we investigate with intrinsic Slater determinants as trial states in how far these two competing pictures prevail in the ground states of C12 and O16. The trial states can describe both the j-j coupling shell-model and α-cluster configurations in a unified way. One-body density distributions of the trial states are calculated and compared to elastic scattering cross section data. The parameters of the trial state are chosen to reproduce the experimental charge radii. A well developed cluster structure is characterized by an enhancement of the differential elastic scattering cross sections, as well as the elastic charge form factors around the first peak positions. The density profiles of the internal regions can also be probed at higher momentum transfer regions beyond the second minimum. With these trial states one can visualize the competition between cluster and shell structure in an intuitive and simple way.

DOI： 10.1103/physrevc.107.l021304

Other URL： http://harvest.aps.org/v2/journals/articles/10.1103/PhysRevC.107.L021304/fulltext

Authorship：Lead author,　Corresponding author   Publishing type：Research paper (scientific journal)  

We investigate the degree of α (He4 nucleus) clustering in the ground-state density profiles of Ti44 and Ti52. Two types of density distributions, shell- and cluster-model configurations, are generated fully microscopically with the antisymmetrized quasi-cluster model, which can describe both the j-j coupling shell and α-cluster configurations in a single scheme. Despite both the models reproducing measured charge radius data, we found that the α clustering significantly diffuses the density profiles near the nuclear surface compared to the ideal j-j coupling shell-model configuration. The effect is most significant for Ti44, while it is less for Ti52 due to the occupation of the 0f7/2 orbits in the Ca48 core. This difference can be detected by measuring proton-nucleus elastic scattering or the total reaction cross section on a carbon target at intermediate energies.

DOI： 10.1103/physrevc.106.044330

Other URL： http://harvest.aps.org/v2/journals/articles/10.1103/PhysRevC.106.044330/fulltext

Publishing type：Research paper (scientific journal)  

We theoretically investigate the fate of a neutron-alpha p-wave resonance in dilute neutron matter, which may be encountered in neutron stars and supernova explosions. While He5 is known as a resonant state that decays to a neutron and an alpha particle in vacuum, this unstable state turns into a stable bound state in the neutron Fermi sea because the decay process is forbidden by the Pauli-blocking effect of neutrons. Such a resonance-to-bound transition assisted by the Pauli-blocking effect can be realized in cold atomic experiments for a quantum mixture near the heteronuclear Feshbach resonance.

DOI： 10.1103/physrevc.106.045807

Other URL： http://harvest.aps.org/v2/journals/articles/10.1103/PhysRevC.106.045807/fulltext

Publishing type：Research paper (scientific journal)  

The root mean square radii of the proton density distribution in O16-24 derived from measurements of charge changing cross sections with a carbon target at ∼900A MeV together with the matter radii portray thick neutron skin for O22-24 despite O22,24 being doubly magic. Imprints of the shell closures at N=14 and 16 are reflected in local minima of their proton radii that provide evidence for the tensor interaction causing them. The radii agree with ab initio calculations employing the chiral NNLOsat interaction, though skin thickness predictions are challenged. Shell model predictions agree well with the data.

DOI： 10.1103/PhysRevLett.129.142502

PubMed

Authorship：Corresponding author   Publishing type：Research paper (scientific journal)  

The total reaction cross section of high-energy nucleus-nucleus collision reflects the nuclear density profiles of the colliding nuclei and is a standard tool to investigate the size properties of short-lived unstable nuclei. This relies on the assumption that the nucleus-nucleus collision is strongly absorptive in the sense of an optical model. However, this property does not hold completely, while incomplete absorption occurs when the overlap density of two colliding nuclei is low enough. In this paper, we propose a way to quantify this incompleteness, i.e., the "blackness" of the total reaction cross section. The significance of this quantification is shown by taking an example of the total reaction cross sections of proton-rich C isotopes.

DOI： 10.1093/ptep/ptac089

Publishing type：Research paper (scientific journal)  

In neutron-rich nuclei neighboring Si-42, the quenching of the N = 28 shell gap occurs and is expected to induce shape coexistence in their excitation spectra. We have applied the theoretical framework of antisymmetrized molecular dynamics with the Gogny D1S density functional to describe the shape coexistence in the N = 28 isotones Mg-40, Si-42, and S-44. We show that different nuclear shapes coexist in these nuclei: Rigid shapes with different deformations coexist in Mg-40 and Si-42, while S-44 exhibits large-amplitude collective motion and does not have any particular shape. These characteristics are reflected well in the monopole transition strengths that can be utilized as a probe for the shape coexistence.

DOI： 10.1093/ptep/ptac071

Authorship：Lead author,　Corresponding author   Publishing type：Research paper (scientific journal)   International / domestic magazine：International journal  

We revisit a sudden increase of the isotope shift of the charge radius of Pb isotopes at N > 126 based on a Skyrme Hartree-Fock-Bogoliubov theory. New parametrizations of the pairing interaction optimized for four selected Skyrme interactions greatly improve a description of this phenomenon. The density-dependent spinorbit interaction is also investigated and further increases the charge radius. The pairing correlations significantly change the properties of the neutron orbits near the Fermi level and play a vital role in pulling out the well-bound protons in the Pb isotopes at N > 126. Regarding Pb-208 as a "core" nucleus, a novel pairing core swelling effect is proposed: The pairing interaction reduces the radius of "valence" neutron orbits by the shrinkage of the diffused 1g(9/2) orbit and the mixing of the sharp 0i(11/2) orbit. Simultaneously, the core nucleus swells, leading to the sudden enhancement of the charge radius at N > 126. This characteristic behavior appears in the density profile near the nuclear surface and its measurement is highly desirable.

DOI： 10.1103/PhysRevC.105.044303

Publishing type：Research paper (scientific journal)  

In order to efficiently describe nucleon orbits around a heavy core nucleus, we propose locally peaked Gaussians orthogonalized to the occupied bound states in the core. We show the advantage of those functions in both numerical stability and fast convergence by taking examples of touchstone calcium isotopes Ca-62,Ca-72 in Ca-60,Ca-70 +n + n three-body models. Both weakly bound configurations and continuum coupling effect are taken into account. We evaluate the neutron radii and the occupation probabilities of two-neutron configurations not only for the ground state but also for some particle-bound excited states by varying the strength of the core-neutron interaction. The emergence of the halo structure in the ground state depends on the energy difference between 2s(1/)(2 )and 0g(9/2) orbits. Two-neutron [consisting of (s(1/2))(2) configuration] and one-neutron [consisting of (g(9/2)s(1/2)) configuration] halo structures of Ca-62 can coexist in narrow energy spacing provided that both of 2s(1/)(2) and 0g(9/2) orbits are almost degenerate and barely bound. The ground-state structure of Ca-72 is likely to be a two-neutron halo, although its emergence depends on the position of the 2s(1/)(2) level.

DOI： 10.1103/PhysRevC.105.024310

Publishing type：Research paper (scientific journal)  

A systematic analysis of nuclear deformation is made for neutron-rich Ti, Cr, and Fe isotopes to explore the nuclear structure in the island of inversion near N = 40, where strong nuclear deformation is predicted. The nuclear ground states are obtained by the Skyrme-Hartree-Fock method in three-dimensional coordinate space, which properly describes any nuclear shape. Three types of Skyrme interactions are employed to generate various deformed states in its isotopic chain. We find that in the island of inversion the occupation of highly elongated intruder orbits induces not only large quadrupole deformation but also large hexadecapole deformation. This appears as a sizable enhancement of the nuclear matter radius, showing the characteristic shell effect of the density profile near the nuclear surface. We show that the edge of the island of inversion, where the intruder orbit starts being occupied, can be determined by measuring the enhancement of the total reaction cross section at high incident energy. The possibility of constraining the hexadecapole deformation by a measurement of the total reaction cross sections is discussed.

DOI： 10.1103/PhysRevC.105.014316

Publishing type：Research paper (scientific journal)  

Nuclear surface diffuseness reflects spectroscopic information near the Fermi level. I propose a way to decompose the surface diffuseness into single-particle (s.p.) contributions in a quantitative manner. Systematic behavior of the surface diffuseness of neutron-rich even-even O, Ca, Ni, Sn, and Pb isotopes is analyzed with a phenomenological mean-field approach. The role of the s.p. wave functions near the Fermi level is explored: The nodeless s.p. orbits form a sharp nuclear surface, while the nodal s.p. orbits contribute to diffusing the nuclear surface.

DOI： 10.1093/ptep/ptab136

Publishing type：Research paper (scientific journal)  

We elucidate the fate of two and three neighboring alpha particles in cold neutron matter by focusing on an analogy between such alpha systems and Fermi polarons realized in ultracold atoms. We describe in-medium excitation properties of an alpha particle and neutron-mediated two- and three-alpha interactions using theoretical approaches developed for studies of cold atomic systems. We numerically solve the few-body Schrodinger equation of alpha particles within standard alpha cluster models combined with in-medium properties of alpha particles. We point out that the resultant two-alpha ground state and three-alpha first excited state, which correspond to 8Be and the Hoyle state, respectively, known as main components in the triple-alpha reaction, can become bound states in such a manyneutron background although these states are unstable in vacuum. Our results suggest a significance of these in-medium cluster states not only in astrophysical environments such as core-collapsed supernova explosions and neutron star mergers but also in neutron-rich nuclei.

DOI： 10.1103/PhysRevC.104.065801

Publishing type：Research paper (scientific journal)  

Background: The density profile of exotic nuclei can be a rich source of information on the nuclear surface. In particular, the nuclear surface diffuseness is correlated with the occupation probability of nucleons in distinct nuclear orbits, especially those with low angular momenta. Purpose: The aim of this paper is to investigate the relationship between the nuclear surface diffuseness and spectroscopic information of neutron-rich Ne and Mg isotopes both at the cusp and inside the island of inversion. Method: We use the microscopic antisymmetrized molecular dynamics model to calculate the densities and other spectroscopic information related to Ne and Mg isotopes. A two-parameter Fermi density distribution is then used to define the diffuseness parameter and the matter radius. These quantities are extracted by minimizing the difference between these two densities. To relate them with observables, the two densities are given as inputs to a Glauber model calculation of nucleon-nucleus elastic scattering differential cross section, with the demand that they reproduce the first peak position and its magnitude. Results: A marked increase in the occupation of neutrons in the pf orbit is noted in Ne and Mg isotopes from N = 19 onwards. We observed that the nuclear surface diffuseness is strongly correlated with the nuclear deformation, in the island of inversion, and gradually increases with the occupation of neutrons in the 1p3/2 orbit. This result is also confirmed by a single-particle estimate of the valence neutron density distribution, with 29Ne as a test case. An exception is noted for 35-37Mg, where the filling up of the holes in the sd shell partially compensates the increase in diffuseness due to filling up of the 1p3/2 orbit. Conclusion: Information on nuclear density profile of neutron-rich medium mass nuclei can be reliably extracted by studying the first diffraction peak of the nucleon-nucleus elastic scattering differential cross section. The enormous surface diffuseness of Ne and Mg isotopes, in the island of inversion, could be attributed to the increasing neutron occupation of the 1p3/2 orbit.

DOI： 10.1103/PhysRevC.104.054313

Publishing type：Research paper (scientific journal)  

<title>Abstract</title>
Mass number dependence of the nuclear radii is closely related to the nuclear matter properties. It is known that the most of nuclei exhibit some deformation. We discuss how the nuclear density profile is modified by the nuclear deformation to elucidate the enhancement mechanism of the nuclear radii through a systematic investigation of neutron-rich Ne, Mg, Si, S, Ar, Ti, Cr, and Fe isotopes. Skyrme-Hartree-Fock calculations are performed in a three-dimensional Cartesian grid to describe the nuclear deformation in a non-empirical way. The role of the nuclear deformation on the nuclear density profiles is explored in comparison to calculations with spherical limit. We find correlations between the nuclear deformation and the internal nuclear density. The evolution of the nuclear radii appears to follow the core swelling mechanism recently proposed in spherical nuclei [Phys. Rev. C 101, 061301(R) (2020)], and the radius is further enhanced by the nuclear deformation. This study demands further theoretical and experimental investigations for the internal density.

DOI： 10.1093/ptep/ptab087

Publishing type：Research paper (scientific journal)  

Nuclear dipole excitation has been used as a probe of nuclear structure. To unveil the structure of various excitation modes proposed up to date, a study of isoscalar (IS) and isovector (IV) dipole excitations has been of particular importance. In this paper, we discuss the possibility of separating the dipole excitation cross sections into the IS and IV contributions using heavy-ion collisions at high-incident energies from 100 to 400 MeV/nucleon. We examine the dipole transitions of Li-6 and He-6 on carbon and lead targets and quantify the nuclear, Coulomb, and their interference contributions. We show that the IS and IV separation can be made in a certain degree of accuracy when appropriate target and incident energies are chosen for each case of Li-6 and He-6. (C) 2021 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.nuclphysa.2021.122204

Publishing type：Research paper (scientific journal)  

<title>Abstract</title>
We propose formulas of the nuclear beta-decay rate that are useful in a practical calculation. The decay rate is determined by the product of the lepton and hadron current densities. A widely used formula relies upon the fact that the low-energy lepton wave functions in a nucleus can be well approximated by a constant and linear to the radius for the s-wave and p-wave wave functions, respectively. We find, however, the deviation from such a simple approximation is evident for heavy nuclei with large Z by numerically solving the Dirac equation. In our proposed formulas, the neutrino wave function is treated exactly as a plane wave, while the electron wave function is obtained by iteratively solving the integral equation, thus we can control the uncertainty of the approximate wave function. The leading-order approximation gives a formula equivalent to the conventional one and overestimates the decay rate. We demonstrate that the next-to-leading-order formula reproduces well the exact result for a schematic transition density as well as a microscopic one obtained by a nuclear energy-density functional method.

DOI： 10.1093/ptep/ptab069

Publishing type：Research paper (scientific journal)  

Background: The neutron-rich F-28,F-29 isotopes have been recently studied via knockout and interaction cross-section measurements. The two-neutron halo in F-29 has been linked to the occupancy of pf intruder configurations.Purpose: We investigate the bound spectrum and continuum states in F-29, focusing on the electric dipole (E1) response of low-lying excitations and the effect of dipole couplings on nuclear reactions.Method: F-29 (F-27 +n + n) wave functions are built within the hyperspherical harmonics expansion formalism, and total reaction cross sections are calculated using the Glauber theory. Continuum states and B(E1) transition probabilities are described in a pseudostate approach using the analytical transformed harmonic oscillator basis. The corresponding structure form factors are used in continuum-discretized coupled-channels (CDCC) calculations to describe low-energy scattering.Results: Parity inversion in F-28 leads to a F-29 ground state characterized by 57.5% of (P-3/2)(2) intruder components, a strong dineutron configuration, and an increase of the matter radius with respect to the core radius of Delta R = 0.20 fm. Glauber-model calculations for a carbon target at 240 MeV/nucleon provide a total reaction cross section of 1370 mb, in agreement with recent data. The model produces also a barely bound excited state corresponding to a quadrupole excitation. B(E1) calculations into the continuum yield a total strength of 1.59 e(2 )fm(2) up to 6 MeV, and the E1 distribution exhibits a resonance at approximate to 0.85 MeV. Results using a standard shell-model order for F-28 lead to a considerable reduction of the B(E1) distribution. The four-body CDCC calculations for F-29 + 120 Sn around the Coulomb barrier are dominated by dipole couplings, which totally cancel the Fresnel peak in the elastic-scattering cross section.Conclusions: Our three-body calculations for F-29, using the most recent experimental information on F-28, are consistent with a two-neutron halo. Our predictions show the low-lying enhancement of the E1 response expected for halo nuclei and the relevance of dipole couplings for low-energy reactions on heavy targets. These findings may guide future experimental campaigns.

DOI： 10.1103/PhysRevC.102.064627

Publishing type：Research paper (scientific journal)  

Light clusters such as alpha particles and deuterons are predicted to occur in hot nuclear matter as encountered in intermediate-energy heavy-ion collisions and protoneutron stars. To examine the in-medium properties of such light clusters, we consider a much simplified system in which, like an impurity, a single alpha particle is embedded in a zero-temperature, dilute gas of noninteracting neutrons. By adopting a non-self-consistent ladder approximation for the effective interaction between the impurity and the gas, which is often used for analyses of Fermi polarons in a gas of ultracold atoms, we calculate the quasiparticle properties of the impurity, i.e., the energy shift, effective mass, quasiparticle residue, and damping rate.

DOI： 10.1103/PhysRevC.102.055802

Publishing type：Research paper (scientific journal)  

Background: Eclipse effect of the neutron and the proton in a deuteron target is essential to correctly describe high-energy deuteron scattering. The nucleus-deuteron scattering needs information on not only the nucleus-proton interaction but also the nucleus-neutron interaction, for which no direct measurement of the nucleus-neutron cross sections is available for unstable nuclei.Purpose: We systematically evaluated the total reaction cross sections on a deuteron target to explore the feasibility of extracting the nucleus-neutron interaction from measurable cross sections.Methods: High-energy nucleus-deuteron collision is described by the Glauber model, in which the proton and neutron configuration of the deuteron is explicitly taken into account.Results: Our calculation reproduces available experimental total reaction cross section data on the nucleus-deuteron scattering. The possibility of extracting the nucleus-neutron total reaction cross section from nucleus-deuteron and nucleus-proton total reaction cross sections is explored. The total reaction cross sections on proton, neutron, and deuteron targets can be expressed, to good accuracy, in terms of the nuclear matter radius and the neutron skin thickness. Incident-energy dependence of the total reaction cross sections is examined.Conclusions: The total reaction cross section on a deuteron target includes information on both the nucleus-neutron and the nucleus-proton profile functions. Measuring the cross sections by deuteron and proton targets is a promising tool to extract the nuclear size properties.

DOI： 10.1103/PhysRevC.102.054601

Publishing type：Research paper (scientific journal)  

The triple-alpha reaction is key to C production and is expected to occur in weakly coupled thermal plasmas as encountered in normal stars. We investigate how Coulomb screening affects the structure of a system of three alpha particles in such a plasma environment by precise three-body calculations within the Debye-Huckel approximation. A three-alpha model that has the Coulomb interaction modified in the Yukawa form is employed. Precise three-body wave functions are obtained by a superposition of correlated Gaussian basis with the aid of the stochastic variational method. The energy shifts of the Hoyle state due to the Coulomb screening are obtained as a function of the Debye screening length. The results, which automatically incorporate the finite-size effect of the Hoyle state, are consistent with the conventional result based on the Coulomb correction to the chemical potentials of ions that are regarded as point charges in a weakly coupled thermal plasma. We have given a theoretical basis to the conventional point-charge approach to the Coulomb screening problem relevant for nuclear reactions in normal stars by providing the first evaluation of the Coulomb corrections to the value of the triple-alpha process that produces a finite-size Hoyle state.

DOI： 10.1093/ptep/ptaa093

Publishing type：Research paper (scientific journal)  

Antiproton-nucleon ((p) over barN) total cross sections are typically 3-4 times larger than the NN ones at incident energies from a few hundreds to thousands MeV. We investigate antiproton-nucleus scattering as it could work as a probe of the nuclear structure giving the sensitivity differently from a proton probe. High-energy antiproton-nucleus reactions are reasonably described by the Glauber model with a minimal profile function that reproduces the (p) over barN and (p) over bar-C-12 cross section data. In contrast to the proton-nucleus scattering, we find that the complete absorption occurs even beyond the nuclear radius due to the large (p) over barN elementary cross sections, which shows stronger sensitivity to the nuclear density distribution in the tail region. This sensitivity is quantified in the total reaction cross sections with various density profiles for future measurement including neutron-rich unstable nuclei.

DOI： 10.1103/PhysRevC.102.034614

Publishing type：Research paper (scientific journal)  

Background: The density of most nuclei is constant in the central region and is smoothly decreasing at the surface. A depletion in the central part of the nuclear density can have nuclear structure effects leading to the formation of "bubble" nuclei. However, probing the density profile of the nuclear interior is, in general, very challenging.Purpose: The aim of this paper is to investigate the nuclear bubble structure, with nucleon-nucleus scattering, and quantify the effect that the bubble structure has on the nuclear surface profile.Method: We employed high-energy nucleon-nucleus scattering, using the Glauber model to analyze various reaction observables, which helps in quantifying the nuclear bubble. The effectiveness of this method is tested on Si-2(8) with harmonic-oscillator (HO) densities, before applying it on even-even N = 14 isotones, in the 22 <= A <= 34 mass range, with realistic densities obtained from antisymmetrized molecular dynamics (AMD).Results: Elastic scattering differential cross sections and reaction probability for the proton-Si-28 reaction are calculated using the HO density to design tests for signatures of the nuclear bubble structure. We then quantify the degree of bubble structure for N = 14 isotones with the AMD densities by analyzing their elastic scattering at 325, 550, and 800 MeV incident energies. The present analyses suggest O-2(2) as the most measurable candidate for a bubble nucleus, among even-even N = 14 isotones, in the 22 <= A <= 34 mass range.Conclusion: We have shown that the bubble structure information is imprinted on the nucleon-nucleus elastic scattering differential cross section, especially in the first diffraction peak. Bubble nuclei tend to have a sharper nuclear surface and deformation seems to be a hindrance in their emergence.

DOI： 10.1103/PhysRevC.102.034619

Publishing type：Research paper (scientific journal)  

The exotic, neutron-rich and weakly-bound isotope(29)F stands out as a waymarker on the southern shore of the island of inversion, a portion of the nuclear chart where the effects of nuclear forces lead to a reshuffling of the single particle levels and to a reorganization of the nuclear structure far from stability. This nucleus has become very popular, as new measurements allow to refine theoretical models. We review the latest developments and suggest how to further assess the structure by proposing predictions on electromagnetic transitions that new experiments of Relativistic Coulomb Excitation should soon become able to measure.The neutron-rich, weakly bound fluorine isotope(29)F has been extensively investigated theoretically, but its significance has been revived by recent experiments. The authors present the latest developments and make prediction on the electromagnetic transitions occurring in this isotope that may be observed in the near future.

DOI： 10.1038/s42005-020-00402-5

Publishing type：Research paper (scientific journal)  

We report the measurement of reaction cross sections (sigma(ex)(R)) of F-27,F-29 with a carbon target at RIKEN. The unexpectedly large sigma(ex)(R) and derived matter radius identify F-29 as the heaviest two-neutron Borromean halo to date. The halo is attributed to neutrons occupying the 2p(3/2) orbital, thereby vanishing the shell closure associated with the neutron number N = 20. The results are explained by state-of-the-art shell model calculations. Coupled-cluster computations based on effective field theories of the strong nuclear force describe the matter radius of F-27 but are challenged for F-29.

DOI： 10.1103/PhysRevLett.124.222504

Publishing type：Research paper (scientific journal)  

Background: Nuclear radius is one of the most important and basic properties of atomic nuclei and its evolution is closely related to the saturation of the nuclear density in the internal region but the systematics of the nuclear radii for the neutron-rich unstable nuclei is not well known.Purpose: Motivated by the recent interaction cross section measurement which indicates the Ca-48 core swelling in the neutron-rich Ca isotopes, we explore the mechanism of the enhancement of the neutron and proton radii for spherical nuclei.Methods: Microscopic Hartree-Fock calculations with three sets of Skyrme-type effective interactions are performed for the neutron-rich Ca, Ni, and Sn isotopes. The total reaction cross sections for the Ca isotopes are evaluated with the Glauber model to compare them with the recent cross section data.Results: We obtain good agreement with the measured cross sections and charge radii. The neutron and proton radii of the various "core" configurations are extracted from the full Hartree-Fock calculation and discuss the core swelling mechanism.Conclusions: The core swelling phenomena occur depending on the properties of the occupying valence single-neutron states to minimize the energy loss that comes from the saturation of the densities in the internal region, which appears to be prominent in light nuclei such as Ca isotopes.

DOI： 10.1103/PhysRevC.101.061301

Publishing type：Research paper (scientific journal)  

Background: A newly identified drip-line nucleus F-31 offers a unique opportunity to study the two-neutron (2n) correlation at the east shore of the island of inversion where the N = 28 shell closure is lost. Purpose: We aim to present the first three-body theoretical results for the radius and total reaction cross sections of F-31. This will further help to investigate how the pairing and the breakdown of the N = 28 shell closure influence the formation of the 2n-halo structure and the antihalo effect in this mass region.Methods: A F-29+n + n three-body system is described by the cluster orbital shell model, and its total reaction cross section is calculated by the Glauber theory.Results: Our three-body calculations predict 3.48-3.70 fm for the root-mean-square radius of F-31, which corresponds to the total reaction cross section of 1530 (1410) to 1640 (1500) mb for a carbon target at 240 (900) MeV/nucleon. The binding mechanism and halo formation in F-31 are discussed.Conclusions: The present study suggests a novel antihalo effect in this mass region: When the pairing overcomes the energy gap between the p(3/2) and f(7/2) orbits, the inversion of the occupation number of these orbits takes place, and it diminishes the 2n-halo structure.

DOI： 10.1103/PhysRevC.101.041303

Publishing type：Research paper (scientific journal)  

Interaction cross sections for Ca42-51 on a carbon target at 280 MeV/nucleon have been measured for the first time. The neutron number dependence of derived root-mean-square matter radii shows a significant increase beyond the neutron magic number N = 28. Furthermore, this enhancement of matter radii is much larger than that of the previously measured charge radii, indicating a novel growth in neutron skin thickness. A simple examination based on the Fermi-type distribution, and mean field calculations point out that this anomalous enhancement of the nuclear size beyond N = 28 results from an enlargement of the core by a sudden increase in the surface diffuseness of the neutron density distribution, which implies the swelling of the bare Ca-48 core in Ca isotopes beyond N = 28.

DOI： 10.1103/PhysRevLett.124.102501

Publishing type：Research paper (scientific journal)  

Background: The F-29 system is located at the lower-N boundary of the "island of inversion" and is an exotic, weakly bound system. Little is known about this system beyond its two-neutron separation energy (S-2n) with large uncertainties. A similar situation is found for the low-lying spectrum of its unbound binary subsystem F-28.Purpose: We investigate the configuration mixing, matter radius, and neutron-neutron correlations in the ground-state of F-29 within a three-body model, exploring the possibility of F-29 to be a two-neutron halo nucleus.Method: The F-29 ground-state wave function is built within the hyperspherical formalism by using an analytical transformed harmonic oscillator basis. The Gogny-Pires-Tourreil (GPT) nn interaction with central, spin-orbit, and tensor terms is employed in the present calculations, together with different core + n potentials constrained by the available experimental information on F-28.Results: The F-29 ground-state configuration mixing and its matter radius are computed for different choices of the F-28 structure and S-2n value. The admixture of d waves with pf components is found to play an important role, favoring the dominance of dineutron configurations in the wave function. Our computed radii show a mild sensitivity to the F-27+n potential and S-2n values. The relative increase of the matter radius with respect to the F-27 core lies in the range 0.1-0.4 fm depending upon these choices.Conclusions: Our three-body results for F-29 indicate the presence of a moderate halo structure in its ground state, which is enhanced by larger intruder components. This finding calls for an experimental confirmation.

DOI： 10.1103/PhysRevC.101.024310

Publishing type：Research paper (scientific journal)  

We measured the energy dependence of the total reaction cross sections (sigma(R)) for the proton drip-line nucleus of neon isotopes, Ne-17, with a solid hydrogen target. The sigma(R) on a proton target in the low- and intermediate-energy regions were provided, where only a few values are available for unstable nuclei. The new data were compared with theoretical calculations using the Glauber model. In the low-energy region (similar to 100A MeV), the theoretical cross sections overestimate the experimental ones, whereas the theoretical ones significantly underestimate the experimental data in the intermediate energy region (similar to 300-500A MeV). We discuss several possibilities for solving this discrepancy. This work suggests the necessity of more careful investigations of the energy dependence of sigma(R) for various nuclei on a proton target to determine the nuclear size properties precisely. (C) 2019 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.nuclphysa.2019.121663

DOI： 10.1007/s00601-019-1518-8

DOI： 10.1103/PhysRevC.100.024334

DOI： 10.1016/j.nuclphysa.2019.02.004

Publishing type：Research paper (scientific journal)  

A thick neutron skin emerges from the first determination of root mean square radii of the proton distributions for 17−22N from charge changing cross section measurements around 900A MeV at GSI. Neutron halo effects are signalled for 22N from an increase in the proton and matter radii. The radii suggest an unconventional shell gap at N = 14 arising from the attractive proton–neutron tensor interaction, in good agreement with shell model calculations. Ab initio, in-medium similarity re-normalization group, calculations with a state-of-the-art chiral nucleon–nucleon and three-nucleon interaction reproduce well the data approaching the neutron drip-line isotopes but are challenged in explaining the complete isotopic trend of the radii.

DOI： 10.1016/j.physletb.2019.01.024

DOI： 10.1103/PhysRevC.99.034605

The first excited J(pi) = 0(+) state of C-12, the so-called Hoyle state, plays an essential role in a triple-alpha (He-4) reaction, which is a main contributor to the synthesis of C-12 in a burning star. We investigate the Coulomb screening effects on the energy shift of the Hoyle state in a thermal plasma environment using precise three-alpha model calculations. The Coulomb screening effect between alpha clusters is taken into account within the Debye-Huckel approximation. To generalize our study, we utilize two standard alpha-cluster models, which treat the Pauli principle between the alpha particles differently. We find that the energy shift does not depend on these models and follows a simple estimation in the zero-size limit of the Hoyle state when the Coulomb screening length is as large as a value typical of such a plasma consisting of electrons and alpha particles.

DOI： 10.1007/s00601-021-01633-0

DOI： 10.1088/1742-6596/1643/1/012099

Other URL： https://iopscience.iop.org/article/10.1088/1742-6596/1643/1/012099

DOI： 10.1088/1742-6596/1643/1/012158

Other URL： https://iopscience.iop.org/article/10.1088/1742-6596/1643/1/012158

DOI： 10.1088/1742-6596/1643/1/012089

Other URL： https://iopscience.iop.org/article/10.1088/1742-6596/1643/1/012089

DOI： 10.7566/jpscp.32.010029

Three-body correlations in three-body exotic atoms are studied with
simple models that consist of three bosons interacting through a
superposition of long- and short-range potentials. We discuss the
correlations among particles by comparing the energy shifts given by
precise three-body calculations and by the Deser-Trueman formula, in
which the long- and short-range contributions are factorized. By varying
the coupling of the short-range potential, we evaluate the ranges of the
strength where the two-body correlations dominate and where the
three-body correlations cannot be neglected.

DOI： 10.21468/scipostphysproc.3.051

Exploring new excitation modes and the role of the nuclear clustering
has been of great interest. An interesting speculation was made in the
recent photoabsorption measurement of <inline-formula><alternatives><tex-math>^6</tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msup><mml:mi /><mml:mn>6</mml:mn></mml:msup></mml:math></alternatives></inline-formula>Li
that implied the importance of the nuclear clustering. To understand the
excitation mechanism of <inline-formula><alternatives><tex-math>^6</tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msup><mml:mi /><mml:mn>6</mml:mn></mml:msup></mml:math></alternatives></inline-formula>Li,
we perform a fully microscopic six-body calculation on the
electric-dipole (<inline-formula><alternatives><tex-math>E1</tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mi>E</mml:mi><mml:mn>1</mml:mn></mml:mrow></mml:math></alternatives></inline-formula>)
transitions and discuss how <inline-formula><alternatives><tex-math>^6</tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msup><mml:mi /><mml:mn>6</mml:mn></mml:msup></mml:math></alternatives></inline-formula>Li
is excited by the <inline-formula><alternatives><tex-math>E1</tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mi>E</mml:mi><mml:mn>1</mml:mn></mml:mrow></mml:math></alternatives></inline-formula>
field as a function of the excitation energy. We show the various
cluster components in the six-body wave functions and discuss the role
of the nuclear clustering in the <inline-formula><alternatives><tex-math>E1</tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mi>E</mml:mi><mml:mn>1</mml:mn></mml:mrow></mml:math></alternatives></inline-formula>
excitations of <inline-formula><alternatives><tex-math>^6</tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msup><mml:mi /><mml:mn>6</mml:mn></mml:msup></mml:math></alternatives></inline-formula>Li.

DOI： 10.21468/scipostphysproc.3.022

Recently, the energy spectrum of <inline-formula><alternatives><tex-math>\boldsymbol{^{10 } }</tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mstyle mathvariant="bold"><mml:msup><mml:mi /><mml:mn>10</mml:mn></mml:msup></mml:mstyle></mml:math></alternatives></inline-formula>Li
was measured upto <inline-formula><alternatives><tex-math>\boldsymbol{4.6}</tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mstyle mathvariant="bold"><mml:mn>4.6</mml:mn></mml:mstyle></mml:math></alternatives></inline-formula> MeV,
via one-neutron transfer reaction <inline-formula><alternatives><tex-math>\boldsymbol{d(^{9}\textrm{Li},~p)^{10}\textrm{Li } }</tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mstyle mathvariant="bold"><mml:mi>𝐝</mml:mi><mml:msup><mml:mo stretchy="false" form="prefix">(</mml:mo><mml:mn>9</mml:mn></mml:msup><mml:mtext mathvariant="normal">Li</mml:mtext><mml:mo>,</mml:mo><mml:mspace width="0.222em" /><mml:mi>𝐩</mml:mi><mml:msup><mml:mo stretchy="false" form="postfix">)</mml:mo><mml:mn>10</mml:mn></mml:msup><mml:mtext mathvariant="normal">Li</mml:mtext></mml:mstyle></mml:math></alternatives></inline-formula>.
Considering the ambiguities on the <inline-formula><alternatives><tex-math>\boldsymbol{^{10 } }</tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mstyle mathvariant="bold"><mml:msup><mml:mi /><mml:mn>10</mml:mn></mml:msup></mml:mstyle></mml:math></alternatives></inline-formula>Li
continuum spectrum with reference to new data, we report the
configuration mixing in the ground state of the two-neutron halo nucleus
<inline-formula><alternatives><tex-math>\boldsymbol{^{11 } }</tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mstyle mathvariant="bold"><mml:msup><mml:mi /><mml:mn>11</mml:mn></mml:msup></mml:mstyle></mml:math></alternatives></inline-formula>Li
for two different choices of the <inline-formula><alternatives><tex-math>\boldsymbol{^{9}{\textrm{Li } }+n}</tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mstyle mathvariant="bold"><mml:msup><mml:mi /><mml:mn>9</mml:mn></mml:msup><mml:mtext mathvariant="normal">Li</mml:mtext><mml:mo>+</mml:mo><mml:mi>𝐧</mml:mi></mml:mstyle></mml:math></alternatives></inline-formula>
potential. For the present study, we employ a three-body
(<inline-formula><alternatives><tex-math>\boldsymbol{\textrm{core}+n+n}</tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mstyle mathvariant="bold"><mml:mtext mathvariant="normal">core</mml:mtext><mml:mo>+</mml:mo><mml:mi>𝐧</mml:mi><mml:mo>+</mml:mo><mml:mi>𝐧</mml:mi></mml:mstyle></mml:math></alternatives></inline-formula>)
structure model developed for describing the two-neutron halo system by
explicit coupling of unbound continuum states of the subsystem
(<inline-formula><alternatives><tex-math>\boldsymbol{\textrm{core}+n}</tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mstyle mathvariant="bold"><mml:mtext mathvariant="normal">core</mml:mtext><mml:mo>+</mml:mo><mml:mi>𝐧</mml:mi></mml:mstyle></mml:math></alternatives></inline-formula>),
and discuss the two-neutron correlations in the ground state of
<inline-formula><alternatives><tex-math>\boldsymbol{^{11 } }</tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mstyle mathvariant="bold"><mml:msup><mml:mi /><mml:mn>11</mml:mn></mml:msup></mml:mstyle></mml:math></alternatives></inline-formula>Li.

DOI： 10.21468/scipostphysproc.3.007

J-GLOBAL

We investigate the spin-flip charge-exchange type nuclear excitations, that are, Gamow-Teller (GT) and isovector-spin-monopole (IVSM) transitions, to explore a possible probe to study the two-neutron correlations in the halo nuclei. A typical light halo nucleus, He-6, is studied with He-4 (alpha) + two-nucleon (N) three-body model. We show that the IVSM transitions are superior to the GT ones to obtain the information on the structure of He-6: The strong IVSM strengths, which are sensitive to the binding energy of He-6, are found in the low-lying region below the alpha+deuteron (d) threshold, whereas the GT strengths have almost no peak due to small overlap between the wave functions of the ground state of He-6 and the alpha + d continuum of Li-6.

DOI： 10.1007/978-3-030-32357-8_38

Towards applications to multi-cluster systems involving heavy clusters, we study properties of a shallow-singular potential generated by supersymmetric transformations from an original deep potential. Changes of the relative wave functions by the transformations are quantified with electric-multipole transitions which give a different radial sensitivity to the wave function depending on their multipolarity. Despite the fact that the original and transformed potentials give exactly the same phase shift, some observables are unfavorably modified. We propose another possible way to obtain a desired supersymmetric potential.

DOI： 10.1007/978-3-030-32357-8_37

In this contribution, we report our recent analysis of the nuclear radius of C-22 with total reaction cross sections on C-12 and H-1 targets. The total reaction cross sections are calculated consistently for both the targets within a reliable microscopic framework, the Glauber theory. The multiple-scattering processes within the Glauber theory is fully taken into account using a Monte Carlo technique. We show that the simultaneous reproduction of the two recent cross section data are not feasible within the error bar and unlikely to obtain the huge matter radius similar to 5 fm.

DOI： 10.1007/978-3-030-32357-8_36

J-GLOBAL

Measurement of root-mean-square radii of proton distributions of N17-22 from charge-changing cross section shows the emergence of thick neutron skin towards the neutron-drip line. Signature of N = 14 shell gap has been found in nitrogen isotopes along with the emergence of neutron halo in N-22. The measured radii are in good agreement with the shell model calculations.

DOI： 10.1051/epjconf/201922301003

DOI： 10.1051/epjconf/201919903003

J-GLOBAL

Presentation type：Oral presentation (invited, special)  

Presentation type：Oral presentation (invited, special)  

Presentation type：Oral presentation (invited, special)  

Presentation type：Oral presentation (invited, special)  

Presentation type：Oral presentation (invited, special)  

Presentation type：Oral presentation (invited, special)  

Presentation type：Oral presentation (invited, special)  

Presentation type：Oral presentation (general)  

Presentation type：Oral presentation (invited, special)  

Presentation type：Public lecture, seminar, tutorial, course, or other speech  

Presentation type：Oral presentation (general)  

Presentation type：Oral presentation (general)  

Presentation type：Oral presentation (general)  

Presentation type：Oral presentation (invited, special)  

Presentation type：Oral presentation (general)  

Presentation type：Oral presentation (invited, special)  

Presentation type：Oral presentation (invited, special)  

Presentation type：Oral presentation (invited, special)  

Presentation type：Oral presentation (invited, special)  

Presentation type：Oral presentation (invited, special)  

Presentation type：Oral presentation (invited, special)  

Presentation type：Oral presentation (invited, special)  

Presentation type：Oral presentation (invited, special)  

Presentation type：Oral presentation (invited, special)  

Presentation type：Oral presentation (invited, special)