The isospin symmetry of atomic nuclei is broken due to the Coulomb interaction and the isospin symmetry breaking part of the nuclear interaction. The former gives the dominant contribution to the isospin symmetry breaking of atomic nuclei, and the latter is a small part of the whole; however, it sometimes gives important contributions to nuclear properties, such as the mass difference of...
The equation of state (EOS) of nuclear matter is important not only for understanding the properties and dynamics of nuclei but also for explaining the astrophysical phenomena, such as neutron stars merger and supernova explosions. Research on the EOS from experimental nuclear physics attempts to determine the behavior near saturation density and symmetric nuclear matter from nuclear...
Neutron-rich isotopes have unique structural properties, such as the neutron halo where weakly bound neutrons are spatially extended from the core. Two-neutron halo nuclei such as $^6$He, $^{11}$Li, and $^{19}$B are especially interesting subject since they are Borromean nuclei. A Borromean nucleus is a bound three-body system where any of the two-body subsystems are unbound. Recent Coulomb...
Search for the Island of Stability (IoS) has been one of the most attractive problems in modern nuclear physics. IoS is predicted to exist in the neutron-rich vicinity near Z = 114, N = 184, the Super Heavy Element (SHE) within are anticipated to have a lifetime longer than a year while the lifetime of SHE synthesized in the lab are on the order of ms. The huge enhancement in the stability is...
I will present a theoretical evaluation of coupled-spin entanglement in the two-proton (2p) radioactive emission [1]. For this purpose, a time-dependent three-body model is utilized [2].
Spin entanglement has been evaluated in terms of the coupled-spin correlation S_{CHSH} for the two fermions. Here this S_{CHSH} is so-called Clauser-Horne-Shimony-Holt (CHSH) indicator. For the two protons...
We have performed a Coulomb excitation experiment of $\rm ^{58}Ti$ and
determined its $B(\rm E2)$ value to study the evolution of collectivity in
the Ti isotopes towards $N=40$.
The neutron number $N=40$ is a magic
number in the harmonic oscillator model.
However, the magic character is not observed in most nuclei because of the
narrowing of the shell gap due to spin-orbit...
Spin-zero pairing correlation in finite nuclei produces a systematic difference between the ground-state energies of even and odd-mass nuclei. We customarily use the odd-even mass staggering when discussing pairing correlation, but it is difficult to precisely calculate the energies of odd-mass ground states, especially in the nuclear density functional theory (DFT). Another physical...
We report on the kinematically complete measurement of the Coulomb breakup of the two-neutron halo nucleus $^{14}$Be on Pb at 220 MeV/nucleon at SAMURAI at RIBF. The previous study [1] showed significantly large E1 excitation of $^{14}$Be at low excitation energies, which was indicative of the revelation of the soft E1 excitation for halo nuclei, while the statistics was low and the...
We used the Relativistic Hartree-Fock theory to calculate the equation of state (EOS) of spin-polarized matter, where the spins of nucleons are biased either up or down. Similar to the slope parameter of the isospin-symmetry energy in spin unpolarized matter, we define the “spin slope parameter” of the spin-symmetry energy to characterize the variation of the energy as the spin polarization is...
The rapid spherical to prolate shape transition at N = 60 in the mid-shell region around Z = 40 has been evidenced from diverse experiments [1-5], and the shape evolution for more neutron-rich nuclei has been of interest because of the emergence of the triaxial degree of freedom. Theoretical predictions suggested further phase transitions such as a shape transition to oblate spheroid [6-8], a...
Determining the equation of state for nuclear matter is one of the primary goals in nuclear physics, and is essential for understanding the macroscopic properties of nuclear matter in equilibrium states in both finite systems (nuclei) and infinite systems (neutron stars). The objective of our study is to derive the density-dependent term L for the symmetry energy, focusing on the symmetry...
In some nuclei, a phenomenon called double beta decay, in which two nucleons simultaneously undergo beta decay, is known to occur rarely. In this case, two neutrinos are emitted. Neutrinos may be Majorana particles, which do not distinguish between particles and antiparticles among Fermi particles. In that case, double beta decay without neutrino emission ($0\nu\beta\beta$) may occur. If the...
One of the primary goals of nuclear physics is to achieve a unified understanding of baryon-baryon interactions based on flavor symmetry and its breaking. Charge symmetry breaking (CSB) represents a part of the flavor symmetry that is violated by nuclear forces, leading to differences in neutron-neutron and proton-proton interactions, as well as in neutron-Lambda and proton-Lambda...
In this study, we discuss the shell structure at $N=32$ and $34$, newly recognized magic numbers in neutron-rich nuclei, in the context of deformation toward $N=40$ based on nuclear mass implications. Mass measurements of isotopes $^{55}$Sc, $^{55-58}$Ti, and $^{55-59}$V were conducted during the first commissioning of the ZD-MRTOF system at the RIBF/RIKEN under the SLOWRI project. The newly...
The parameter set of many kinds of density functionals are designed not only to reproduce the basic properties of finite nuclei but also to satisfy the saturation properties of nuclear matter. Consequently, calculations using density functionals can describe experimental data in various mass regions. However, the mean-field calculations using the functionals miss some many-body...
The energy density functional method provides a systematic approach to analyzing nuclear properties across the entire nuclear chart. We have performed calculations for nuclei from the proton drip line to the neutron drip line, including superheavy nuclei. Using the HFBTHO program (Axially deformed solution of the Skyrme-Hartree–Fock–Bogoliubov equations using the transformed harmonic...
Very neutron-rich isotopes, including 28−32Ne, in the vicinity of N = 20 are known to exhibit ground states dominated by fp-shell intruder configurations: the "island of inversion." Systematics for the Ne-isotopic chain suggest that such configurations may be in strong competition with normal shell-model configurations in the ground state of 29Ne. A determination of the structure of 29Ne is...
The issue of tritium water caused by the Fukushima nuclear power plant disaster has become a social problem. In this presentation, the tritium transmutation reaction to 3He is analyzed and reported from the viewpoint of ab-initio calculation of nuclear force.
We present a statistical analysis of nuclear low-lying states within the framework of multireference covariant density functional theory (MR-CDFT) using a relativistic point-coupling energy density functional (EDF). This study is made possible by the newly developed subspace-projected (SP)-CDFT, where the wave functions of nuclear low-lying states for target EDF parameter sets are expanded in...
We have investigated the nuclear structure properties of the medium-heavy nucleus like Cd isotopes in the framework of the nuclear shell model.
We have used the ab initio shell model Hamiltonian from the in-medium Similarity Renormalization Group (IMSRG) approach.
Here, two types of IMSRG approaches have been used, namely IMSRG(2) and a factorized approximation of IMSRG(3).
In this work,...
The study of isomeric states in nuclei is crucial for understanding the nuclear structure, as these states often exhibit structures significantly different from their ground states. The neutron-rich nucleus $^{12}$Be has an isomeric $0^{+}_{2}$ at $E_x = 2.3$ MeV with a half-life of 230 ns (see level diagram in the upper right of Fig. 1). This state undergoes deexcitation via an E2 transition...
Shape coexistence has been observed in nuclei located close to the “Island of Inversion”, where the disappearance of the magic number N = 20 is well known. This nuclear structure is one of the important topics that has been extensively studied both experimentally and theoretically. Our group has systematically investigated nuclear structure in this mass region, focusing on the isotopes of Mg...
The charge density distributions of nuclei, ρ(r), are the best determined by elastic electron scattering, and those of the stable nuclei that have been studied so far have played an essential role in revealing their internal structure.
Recently, the 4th-order moment of the charge density distribution, $
Exploring the nuclear shell structure of neutron-rich $N=50$ nuclei is one of the most interesting and mysterious phenomena in nuclear physics, and it has become the forefront of both experimental and theoretical research in recent years. We have constructed the shell model Hamiltonian in the $\pi(fp)$-$\nu(sdg)$ model space based on {\it ab-initio} approach VS-IMSRG($3{\rm f}_2$) with...
Can alpha particles be the basic building blocks of atomic nuclei? The conventional mean-field picture with nucleons as basic degrees of freedom is considered to dominate, particularly in the ground state of the doubly magic nucleus 16O. On the other hand, alpha cluster theories have predicted their existence in the ground state of 16O [1, 2, 3]. Recently, proton-induced alpha-knockout...
The doubly-magic nucleus $^{132}$Sn and its surrounding nuclei are expected to provide crucial insights into the nuclear shell model structure. In order to extend the nuclear structure studies for low lying states so far, here we carried out the measurement of nuclear magnetic moments of $^{130}$Sn and $^{132}$Sn, by focusing on their higher spin isomeric states. The $^{130}$Sn and $^{132}$Sn...
Density functional theory, widely adopted in nuclear physics, incorporates many-body correlations by expressing the interaction between nucleons constituting a nucleus using a density-dependent Hamiltonian. In addition to two-body nuclear forces, three-body nuclear forces are known to be important in the interaction between nucleons, and density functional theories of the Skyrme and Gogny...
The interaction cross section is a key physical quantity for deducing nuclear radii and plays an essential role in understanding nuclear structure, particularly for neutron-rich isotopes. In this study, we measured the interaction cross sections of Al, Si, and P isotopes near Z=14 to investigate their mass-number dependence and explore nuclear deformation effects.
The experiment was carried...
The interaction cross section is one of the physical quantities that can be used to deduce the nuclear radius, and its measurement contributes to the understanding of the structure of unstable nuclei. While charge radii provide information about the proton distribution, deriving nuclear matter radii from interaction cross sections allows us to gain additional insights into the neutron...
In the 1950s, Bohr and Mottelson established the picture that most heavy nuclei deform into a prolate shape consisting of one long axis and two short axes of equal length.
However, the recent theoretical calculation by T. Otsuka et al.[1] indicates that these nuclei prefer a triaxial shape, with all three axes having different lengths. Additionally, the presence of excited states due to...
