arXiv subjects

M. Dozono

Publications and source records attributed to M. Dozono.

At least 19 recordsLinked to original sources

arXiv2026

Isoscalar Giant Resonances in the even-A Pd Isotopes

Studies of the isoscalar giant monopole resonance (ISGMR) across the chart of nuclides provide insight into the incompressibility of nuclear matter near saturation density, K(infinity). Such studies had revealed a discrepancy between theoretical approaches: quasiparticle random phase approximation (QRPA) derived from Skyrme interactions reproduce the strength distributions of the ISGMR in the doubly-closed-shell nuclei 90Zr and 208Pb, but their descriptions of strength distributions in open-shell medium-heavy nuclei suggest higher centroid energies should be experimentally observed. The latter nuclei required a smaller K(infinity) and were thus deemed softer. The present work serves to add to this softness discourse by extracting ISGMR strength distributions for 104,106,108,110Pd via 386-MeV inelastic alpha-scattering. The extracted giant resonance strength distributions are consistent with expectations in this isotopic range. Additional Quasiparticle Vibration Coupling (QPVC) effects are included with the QRPA approach and compared to aforementioned ISGMR strength distributions.

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arXiv2026

Single-particle strength toward N = 32: Spectroscopy of 51 Ca via the 50 Ca(d, p) reaction

States in the neutron-rich isotope 51 Ca were populated via the 50 Ca(d, p) transfer reaction in inverse kinematics at a beam energy of about 14 AMeV. The experiment was performed using a decelerated radioactive 50 Ca beam from the OEDO facility and the TiNA2 silicon array in combination with the SHARAQ magnetic spectrometer at RIBF/RIKEN. The energies of excited states in 51 Ca were reconstructed via missing mass spectroscopy, and angular distributions of protons were measured to extract differential cross sections. From a comparison with adiabatic distorted wave approximation (ADWA) calculations, spectroscopic factors were deduced for several states, including the ground state and excited states up to 4.2 MeV. These results are compared with shell-model calculations, as well as ab initio valence-space in-medium similarity renormalization group (VS-IMSRG) predictions. The data support the assignment of the 1/2- and 5/2- single-particle states and provide evidence for a candidate 9/2+ state with a structure consistent with neutron excitation into the 0g9/2 orbital. These findings contribute new constraints on the single-particle structure and shell evolution in neutron-rich calcium isotopes.

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arXiv2026

First Extraction of the Matter Radius of $^{132}$Sn via Proton Elastic Scattering at 200 MeV/Nucleon

The angular distribution of the differential cross sections for proton elastic scattering from $^{132}$Sn at 196-210 MeV/nucleon was successfully measured over a momentum transfer range of 0.80 to 2.1 fm$^{-1}$. Using a relativistic impulse approximation, the root-mean-square matter radius of $^{132}$Sn was extracted to be $4.758^{+0.023}_{-0.024}$ fm, which was compared with the state-of-the-art ab initio calculations. Combined with the charge radius measured at ISOLDE, there are no theoretical calculations consistent with both matter and charge radii within the experimental errors.

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arXiv2026

Observation of a broad $p$-wave resonant state in $^{9}$He

We report on the two-body invariant-mass spectroscopy of $^{9}$He, populated via the 1$p$1$n$ knockout reaction from the two-neutron halo nucleus $^{11}$Li at $\sim$250 MeV/nucleon. A broad $p$-wave resonant state of $^{9}$He was observed at 1.28(1) MeV with a width of 0.82(4) MeV.

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arXiv2025

Evolution of two-neutrons configuration from 11Li to 13Li

In this work we investigate the two-neutron decay of 13Li and of the excited states of 11Li populated via one-proton removal from 14Be and 12Be, respectively. A phenomenological model is used to describe the decay of 11Li and 13Li. While the first one displays important sequential components, the second one appears dominated by the direct two-neutron decay. A microscopic three-body model is used to extract information on the spatial configuration of the emitted neutrons before the decay and shows that the average distance between the neutrons increases going from 11Li to 13Li.

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arXiv2024

Mass, spectroscopy and two-neutron decay of $^{16}$Be

The structure and decay of the most neutron-rich beryllium isotope, $^{16}$Be, has been investigated following proton knockout from a high-energy $^{17}$B beam. Two relatively narrow resonances were observed for the first time, with energies of $0.84(3)$ and $2.15(5)$ MeV above the two-neutron decay threshold and widths of $0.32(8)$ and $0.95(15)$ MeV respectively. These were assigned to be the ground ($J^{\pi}=0^+$) and first excited ($2^+$) state, with $E_x=1.31(6)$ MeV. The mass excess of $^{16}$Be was thus deduced to be $56.93(13)$ MeV, some $0.5$ MeV more bound than the only previous measurement. Both states were observed to decay by direct two-neutron emission. Calculations incorporating the evolution of the wavefunction during the decay as a genuine three-body process reproduced the principal characteristics of the neutron-neutron energy spectra for both levels, indicating that the ground state exhibits a strong spatially compact dineutron component, while the 2$^+$ level presents a far more diffuse neutron-neutron distribution.

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arXiv2023

Searching for universality of dineutron correlation at the surface of Borromean nuclei

The dineutron correlation is systematically studied in three different Borromean nuclei near the neutron dripline, 11Li, 14Be and 17B, via the (p, pn) knockout reaction measured at the RIBF facility in RIKEN. For the three nuclei, the correlation angle between the valence neutrons is found to be largest in the same range of intrinsic momenta, which can be associated to the nuclear surface. This result reinforces the prediction that the formation of the dineutron is universal in environments with low neutron density, such as the surface of neutron-rich Borromean nuclei.

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arXiv2021

Quasi-free Neutron Knockout Reaction Reveals a Small $s$-orbital Component in the Borromean Nucleus $^{17}$B

A kinematically complete quasi-free $(p,pn)$ experiment in inverse kinematics was performed to study the structure of the Borromean nucleus $^{17}$B, which had long been considered to have neutron halo. By analyzing the momentum distributions and exclusive cross sections, we obtained the spectroscopic factors for $1s_{1/2}$ and $0d_{5/2}$ orbitals, and a surprisingly small percentage of 9(2)$\%$ was determined for $1s_{1/2}$. Our finding of such a small $1s_{1/2}$ component and the halo features reported in prior experiments can be explained by the deformed relativistic Hartree-Bogoliubov theory in continuum, revealing a definite but not dominant neutron halo in $^{17}$B. The present work gives the smallest $s$- or $p$-orbital component among known nuclei exhibiting halo features, and implies that the dominant occupation of $s$ or $p$ orbitals is not a prerequisite for the occurrence of neutron halo.

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arXiv2020

Surface localization of the dineutron in $^{11}$Li

The formation of a dineutron in the nucleus $^{11}$Li is found to be localized to the surface region. The experiment measured the intrinsic momentum of the struck neutron in $^{11}$Li via the $(p,pn)$ knockout reaction at 246 MeV/nucleon. The correlation angle between the two neutrons is, for the first time, measured as a function of the intrinsic neutron momentum. A comparison with reaction calculations reveals the localization of the dineutron at $r\sim3.6$ fm. The results also support the density dependence of dineutron formation as deduced from Hartree-Fock-Bogoliubov calculations for nuclear matter.

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arXiv2020

Parity-transfer $({}^{16}{\rm O},{}^{16}{\rm F}(0^-,{\rm g.s.}))$ reaction as a selective probe of isovector $0^-$ states in nuclei

We demonstrate that the parity-transfer $({}^{16}{\rm O},{}^{16}{\rm F}(0^-,{\rm g.s.}))$ reaction provides a selective probe of isovector $0^-$ excitations in nuclei. This reaction selectively populates unnatural-parity states through a $0^+ \to 0^-$ transition in the projectile. The excitation-energy spectrum of $^{12}\mathrm{B}$ was reconstructed via the ${}^{12}{\rm C}({}^{16}{\rm O},{}^{16}{\rm F}(0^-,{\rm g.s.}))$ reaction at 247~MeV/u from the coincident detection of the ${}^{15}\mathrm{O}+p$ decay products of ${}^{16}\mathrm{F}$. The known $0^{-}$ state at $E_x = 9.3~{\rm MeV}$ was clearly observed with an enhanced forward cross section, confirming the selectivity of the reaction. Structures observed at $E_x = 6.6 \pm 0.4$ and $14.8 \pm 0.3~{\rm MeV}$ exhibit forward-peaked angular distributions and are suggested to contain significant $0^-$ strength. These results demonstrate that the parity-transfer reaction provides a powerful probe of $0^-$ excitations and highlight its potential for systematic studies of spin-isospin modes, including pion-related dynamics, in nuclei.

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arXiv2019

Structure of 13Be probed via quasi-free scattering

We present an investigation of the structure of 13Be obtained via a kinematically complete measurement of the (p; pn) reaction in inverse kinematics at 265 MeV/nucleon. The relative energy spectrum of 13Be is compared to Transfer-to-the-Continuum calculations which use as structure inputs the overlaps of the 14Be ground-state wave function, computed in a three-body model, with the unbound states of the 13Be residual nucleus. The key role of neutron p-wave orbital in the interpretation of the low-relative-energy part of the spectrum is discussed.

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arXiv2018

How different is the core of $^{25}$F from $^{24}$O$_{g.s.}$?

The neutron-shell structure of $^{25}$F was studied using quasi-free (p,2p) knockout reaction at 270A MeV in inverse kinematics. The sum of spectroscopic factors of $\pi$0d$_{5/2}$ orbital is found to be $1.0 \pm 0.3$. However, the spectroscopic factor for the ground-state to ground-state transition ($^{25}$F, $^{24}$O$_{g.s.}$) is only $0.36\pm 0.13$, and $^{24}$O excited states are produced from the 0d$_{5/2}$ proton knockout. The result shows that the $^{24}$O core of $^{25}$F nucleus significantly differs from a free $^{24}$O nucleus, and the core consists of 35% $^{24}$O$_{g.s}$. and 65% excited $^{24}$O.

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arXiv2016

Separated flow operation of the SHARAQ spectrometer for in-flight proton decay experiments

New operation mode, "separated flow mode", has been developed for in-flight proton decay experiments with the SHARAQ spectrometer. In the separated flow mode, the protons and the heavy-ion products are separated and measured in coincidence at two different focal planes of SHARAQ. The ion-optical properties of the new mode were studied by using a proton beam at $246~{\rm MeV}$, and the momentum vector was properly reconstructed from the parameters measured in the focal plane of SHARAQ. In the experiment with the $({}^{16}{\rm O},{}^{16}{\rm F})$ reaction at a beam energy of $247~{\rm MeV/u}$, the outgoing ${}^{15}{\rm O}+p$ produced by the decay of ${}^{16}{\rm F}$ were measured in coincidence with SHARAQ. High energy resolutions of $100~{\rm keV}$ (FWHM) and $\sim 2~{\rm MeV}$ were achieved for the relative energy of $535~{\rm keV}$, and the ${}^{16}{\rm F}$ energy of $3940~{\rm MeV}$, respectively.

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arXiv2012

Pygmy dipole resonance in 208Pb

Scattering of protons of several hundred MeV is a promising new spectroscopic tool for the study of electric dipole strength in nuclei. A case study of 208Pb shows that at very forward angles J^pi = 1- states are strongly populated via Coulomb excitation. A separation from nuclear excitation of other modes is achieved by a multipole decomposition analysis of the experimental cross sections based on theoretical angular distributions calculated within the quasiparticle-phonon model. The B(E1) transition strength distribution is extracted for excitation energies up to 9 MeV, i.e., in the region of the so-called pygmy dipole resonance (PDR). The Coulomb-nuclear interference shows sensitivity to the underlying structure of the E1 transitions, which allows for the first time an experimental extraction of the electromagnetic transition strength and the energy centroid of the PDR.

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arXiv2011

Complete set of polarization transfer observables for the ${}^{16}{\rm O}(\vec{p},\vec{n}){}^{16}{\rm F}$ reaction at 296 MeV and 0 degrees

We report measurements of the cross section and a complete set of polarization transfer observables for the ${}^{16}{\rm O}(\vec{p},\vec{n}){}^{16}{\rm F}$ reaction at a bombarding energy of $T_p$ = 296 MeV and a reaction angle of $θ_{\rm lab}$ = $0^{\circ}$. The data are compared with distorted-wave impulse approximation calculations employing the large configuration-space shell-model (SM) wave functions. The well-known Gamow-Teller and spin-dipole (SD) states at excitation energies of $E_x$ $\lesssim$ 8 MeV have been reasonably reproduced by the calculations except for the spin--parity $J^π$ = $2^-$ state at $E_x$ = 5.86 MeV. The SD resonance at $E_x$ $\simeq$ 9.5 MeV appears to have more $J^π$ = $2^-$ strength than $J^π$ = $1^-$ strength, consistent with the calculations. The data show significant strength in the spin-longitudinal polarized cross section $ID_L(0^{\circ})$ at $E_x$ $\simeq$ 15 MeV, which indicates existence of the $J^π$ = $0^-$ SD resonance as predicted in the SM calculations.

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arXiv2011

Three Nucleon Force Effects in Intermediate Energy Deuteron Analyzing Powers for dp Elastic Scattering

A complete high precision set of deuteron analyzing powers for elastic deuteron-proton ($dp$) scattering at 250 MeV/nucleon (MeV/N) has been measured. The new data are presented together with data from previous measurements at 70, 100, 135 and 200 MeV/N. They are compared with the results of three-nucleon (3N) Faddeev calculations based on modern nucleon-nucleon (NN) potentials alone or combined with two models of three nucleon forces (3NFs): the Tucson-Melbourne 99 (TM99) and Urbana IX. At 250 MeV/N large discrepancies between pure NN models and data, which are not resolved by including 3NFs, were found at c.m.\ backward angles of $θ_{\rm c.m.}\gtrsim 120^\circ$ for almost all the deuteron analyzing powers. These discrepancies are quite similar to those found for the cross section at the same energy. We found small relativistic effects that cannot resolve the discrepancies with the data indicating that other, short-ranged 3NFs are required to obtain a proper description of the data.

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arXiv2011

Complete electric dipole response and the neutron skin in 208Pb

A benchmark experiment on 208Pb shows that polarized proton inelastic scattering at very forward angles including 0° is a powerful tool for high-resolution studies of electric dipole (E1) and spin magnetic dipole (M1) modes in nuclei over a broad excitation energy range to test up-to-date nuclear models. The extracted E1 polarizability leads to a neutron skin thickness r_skin = 0.156+0.025-0.021 fm in 208Pb derived within a mean-field model [Phys. Rev. C 81, 051303 (2010)], thereby constraining the symmetry energy and its density dependence, relevant to the description of neutron stars.

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arXiv2009

Polarization transfer measurements for $^{12}{\rm C}(\vec{p},\vec{n})^{12}{\rm N (g.s.},1^+)$ at 296 MeV and nuclear correlation effects

Differential cross sections and complete sets of polarization observables are presented for the Gamow-Teller $^{12}{\rm C}(\vec{p},\vec{n})^{12}{\rm N}({\rm g.s.},1^+)$ reaction at a bombarding energy of 296 MeV with momentum transfers $q$ of 0.1 to $2.2{\rm fm}^{-1}$. The polarization transfer observables are used to deduce the spin-longitudinal cross section, $ID_q$, and spin-transverse cross sections, $ID_p$ and $ID_n$. The data are compared with calculations based on the distorted wave impulse approximation (DWIA) using shell-model wave functions. Significant differences between the experimental and theoretical results are observed for all three spin-dependent $ID_i$ at momentum transfers of $q \gtrsim 0.5{\rm fm}^{-1}$, suggesting the existence of nuclear correlations beyond the shell model. We also performed DWIA calculations employing random phase approximation (RPA) response functions and found that the observed discrepancy is partly resolved by the pionic and rho-mesonic correlation effects.

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