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island of inversion; First study of low-lying bound excited states in 
V and 
VElekes, Z.*; Juh
sz, M. M.*; Sohler, D.*; Sieja, K.*; Yoshida, Kazuki; Ogata, Kazuyuki*; Doornenbal, P.*; Obertelli, A.*; Achouri, N. L.*; Baba, Hidetada*; et al.
Physical Review C, 106(6), p.064321_1 - 064321_10, 2022/12
Times Cited Count：0The low-lying level structure of V and V was investigated for the first time. The neutron knockout reaction and inelastic proton scattering were applied for V while the neutron knock-out reaction provided the data for V. Four and five new transitions were determined for V and V, respectively. Based on the comparison to our shell-model calculations using the Lenzi-Nowacki-Poves-Sieja (LNPS) interaction, three of the observed 
rays for each isotope could be placed in the level scheme and assigned to the decay of the first 11/2
and 9/2 levels. The (
,
) excitation cross sections for V were analyzed by the coupled-channels formalism assuming quadrupole plus hexadecapole deformations. Due to the role of the hexadecapole deformation, V could not be unambiguously placed on the island of inversion.
Chazono, Yoshiki*; Yoshida, Kazuki; Ogata, Kazuyuki*
Physical Review C, 106(6), p.064613_1 - 064613_10, 2022/12
Times Cited Count：0 Percentile：0.02(Physics, Nuclear)As a new cluster phenomenon in nuclei, a deuteron like pn cluster is in our interest. The traditional alpha cluster state can be probed by the knockout reaction analysis assuming the alpha particle is inert because the alpha particle is tightly bound. On the other hand, since deuteron is fragile, deuteron cannot be treated as an inert particle in describing the reaction. In this work, we treated the breakup and reformation of the deuteron (p-n pair) by describing the p, n, and the reaction residue in the final channel as a three body scattering state using the continuum discretized coupled channels method. We showed that the interference between the deuteron ground state and the breakup states are strong and has to be included in the deuteron knockout reaction analysis.
neutron orbital and the 
shell closure in 
CaEnciu, M.*; Liu, H. N.*; Obertelli, A.*; Doornenbal, P.*; Nowacki, F.*; Ogata, Kazuyuki*; Poves, A.*; Yoshida, Kazuki; Achouri, N. L.*; Baba, Hidetada*; et al.
Physical Review Letters, 129(26), p.262501_1 - 262501_7, 2022/12
Times Cited Count：0 Percentile：0(Physics, Multidisciplinary)The one-neutron knockout from Ca was performed at 
230 MeV/nucleon combined with prompt spectroscopy. The momentum distributions corresponding to the removal of 
and 
neutrons were measured. The cross sections are consistent with a shell closure at the neutron number , found as strong as at 
and 
in Ca isotopes from the same observables. The analysis of the momentum distributions leads to a difference of the root-mean-square radii of the neutron 
and orbitals of 0.61(23) fm, in agreement with the modified-shell-model prediction of 0.7 fm suggesting that the large root-mean-square radius of the orbital in neutron-rich Ca isotopes is responsible for the unexpected linear increase of the charge radius with the neutron number.
Ca; Spectroscopy of 
K, Ca, and 
CaKoiwai, Takuma*; Wimmer, K.*; Doornenbal, P.*; Obertelli, A.*; Barbieri, C.*; Duguet, T.*; Holt, J. D.*; Miyagi, Takayuki*; Navrtil, P.*; Ogata, Kazuyuki*; et al.
Physics Letters B, 827, p.136953_1 - 136953_7, 2022/04
Times Cited Count：2 Percentile：67.14(Astronomy & Astrophysics)no abstracts in English
Nakayama, Shinsuke; Iwamoto, Osamu; Watanabe, Yukinobu*; Ogata, Kazuyuki*
Few-Body Systems, 63(1), p.4_1 - 4_6, 2022/03
Times Cited Count：0 Percentile：0(Physics, Multidisciplinary)Intensive neutron sources using deuteron accelerators have been proposed for not only science and engineering fields but also medical applications. For the engineering design of such facilities, accurate and comprehensive nuclear data of deuteron-induced reactions are indispensable. However, it is difficult to meet the requirement by employing experimental data alone. Thus, theoretical model calculations play a key role in completing the necessary nuclear data by interpolation and extrapolation of experimental data. Under the above situations, we have been developing a code system dedicated for deuteron-induced reactions, called DEURACS. In the present work, calculations using DEURACS are compared with available experimental data and validation of the present modelling in DEURACS is discussed. Moreover, the importance of consideration of the breakup processes for accurate prediction of deuteron-induced reactions is also presented.
,
) reaction analysis within the distorted-wave impulse approximation frameworkYoshida, Kazuki; Atkinson, M. C.*; Ogata, Kazuyuki*; Dickhoff, W. H.*
Physical Review C, 105(1), p.014622_1 - 014622_7, 2022/01
Times Cited Count：0 Percentile：0.02(Physics, Nuclear)We apply the dispersive optical model (DOM) wave functions to the traditional (,) analysis and investigate the consistency of the DOM spectroscopic factor that describes the (
,
) cross section with the result of the (,) analysis. DOM + distorted wave impulse approximation analysis on 
Ca(,)
K data generates a proton 
spectroscopic factor of 0.560, which is meaningfully smaller than the DOM value of 0.71 shown to be consistent with the (,) analysis. The inconsistency in the spectroscopic factor suggests there is urgent need for improving the description of - scattering in a nucleus.
Cl isotopesLinh, B. D.*; Corsi, A.*; Gillibert, A.*; Obertelli, A.*; Doornenbal, P.*; Barbieri, C.*; Chen, S.*; Chung, L. X.*; Duguet, T.*; G
mez-Ramos, M.*; et al.
Physical Review C, 104(4), p.044331_1 - 044331_16, 2021/10
Times Cited Count：2 Percentile：32.08(Physics, Nuclear)no abstracts in English
Nakayama, Shinsuke; Iwamoto, Osamu; Watanabe, Yukinobu*; Ogata, Kazuyuki*
Journal of Nuclear Science and Technology, 58(7), p.805 - 821, 2021/07
Times Cited Count：10 Percentile：96.35(Nuclear Science & Technology)Intensive fast neutron sources using deuteron accelerators have been proposed for various applications. To contribute to the design study of such neutron sources, a deuteron nuclear data library for 
Li, 
Be, and 
C up to 200 MeV, JENDL/DEU-2020 is developed. The evaluation of JENDL/DEU-2020 are performed by employing the code system DEURACS with particular attention to neutron production data. Toward the evaluation of JENDL/DEU-2020, some modifications are made to DEURACS. The validation of the library is performed though simulation with the Monte Carlo transport calculation codes. From the simulation, it is shown that the calculation results based on JENDL/DEU-2020 reproduce the measured neutron production data well in the incident energies up to 200 MeV. The new library is expected to make a large contribution to diverse design studies of deuteron accelerator neutron sources.
Ca from direct reactionsBrowne, F.*; Chen, S.*; Doornenbal, P.*; Obertelli, A.*; Ogata, Kazuyuki*; Utsuno, Yutaka; Yoshida, Kazuki; Achouri, N. L.*; Baba, Hidetada*; Calvet, D.*; et al.
Physical Review Letters, 126(25), p.252501_1 - 252501_7, 2021/06
Times Cited Count：4 Percentile：45.66(Physics, Multidisciplinary)Direct proton-knockout reactions of Sc were studied at the RIKEN Radioactive Isotope Beam Factory. Populated states of Ca were investigated through -ray and invariant-mass spectroscopy. Level energies were calculated from the nuclear shell model employing a phenomenological inter-nucleon interaction. Theoretical cross sections to states were calculated from distorted-wave impulse approximation estimates multiplied by the shell model spectroscopic factors. Despite the calculations showing a significant amplitude of excited neutron configurations in the ground-state of Sc, valence proton removals populated predominantly the ground-state of Ca. This counter-intuitive result is attributed to pairing effects leading to a dominance of the ground-state spectroscopic factor. Owing to the ubiquity of the pairing interaction, this argument should be generally applicable to direct knockout reactions from odd-even to even-even nuclei.
-particle preformation in 
Ti probed by the (,
) reactionTaniguchi, Yasutaka*; Yoshida, Kazuki; Chiba, Yohei*; Kanada-En'yo, Yoshiko*; Kimura, Masaaki*; Ogata, Kazuyuki*
Physical Review C, 103(3), p.L031305_1 - L031305_5, 2021/03
Times Cited Count：6 Percentile：86.19(Physics, Nuclear)Based on the Ti(,)
Ca reaction analysis, this study reports that -particle formation in the medium-mass Ti nucleus is pronounced more compared to that expected through mean-field approximations. Moreover, the estimated average distance between the particle and residue equals approximately 4.5 fm. This result poses a challenge to describe the four nucleon correlations using microscopic nuclear models.
Ar by the (,2) reactionJuhsz, M. M.*; Elekes, Z.*; Sohler, D.*; Utsuno, Yutaka; Yoshida, Kazuki; Otsuka, Takaharu*; Ogata, Kazuyuki*; Doornenbal, P.*; Obertelli, A.*; Baba, Hidetada*; et al.
Physics Letters B, 814, p.136108_1 - 136108_8, 2021/03
Times Cited Count：2 Percentile：32.08(Astronomy & Astrophysics)The nuclear structure of Ar was studied by the (,2) reaction using -ray spectroscopy for the bound and unbound states. Comparing the results to our shell-model calculations, two bound and six unbound states were established. The low cross sections populating the two bound states of Ar could be interpreted as a clear signature for the presence of significant sub-shell closures at neutron numbers 32 and 34 in argon isotopes.
Chazono, Yoshiki*; Yoshida, Kenichi*; Yoshida, Kazuki; Ogata, Kazuyuki*
Physical Review C, 103(2), p.024609_1 - 024609_7, 2021/02
Times Cited Count：2 Percentile：53.07(Physics, Nuclear)The isoscalar 
pair is expected to emerge in nuclei. We aim to clarify the correspondence between the pairing strength in many-body calculation and the cross section of proton-induced deuteron knockout (, 
) reaction on 
O. The radial wave function of the isoscalar pair with respect to the center of O is calculated with the energy density functional (EDF) approach and is implemented in the distorted wave impulse approximation framework. The pairing strength 
in the EDF calculation is varied and the corresponding change in the cross section is investigated. A clear dependence of the cross section is found. The nuclear distortion is found to make the dependence stronger. Because of the clear -coross section correspondence, the (, ) reaction will be a promising probe for the isoscalar pair in nuclei. For quantitative discussion, further modification of the description of the reaction process will be necessary.
-Orbital component in the Borromean nucleus 
BYang, Z. H.*; Kubota, Yuki*; Corsi, A.*; Yoshida, Kazuki; Sun, X.-X.*; Li, J. G.*; Kimura, Masaaki*; Michel, N.*; Ogata, Kazuyuki*; Yuan, C. X.*; et al.
Physical Review Letters, 126(8), p.082501_1 - 082501_8, 2021/02
Times Cited Count：25 Percentile：96.89(Physics, Multidisciplinary)A quasifree (,) experiment was performed to study the structure of the Borromean nucleus B, which had long been considered to have a neutron halo. By analyzing the momentum distributions and exclusive cross sections, we obtained the spectroscopic factors for 
and 
orbitals, and a surprisingly small percentage of 9(2)% was determined for . Our finding of such a small 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 B. The present work gives the smallest - or -orbital component among known nuclei exhibiting halo features and implies that the dominant occupation of or orbitals is not a prerequisite for the occurrence of a neutron halo.
clusters in dilute neutron-rich matterTanaka, Junki*; Yang, Z.*; Typel, S.*; Adachi, Satoshi*; Bai, S.*; Van Beek, P.*; Beaumel, D.*; Fujikawa, Yuki*; Han, J.*; Heil, S.*; et al.
Science, 371(6526), p.260 - 264, 2021/01
Times Cited Count：22 Percentile：98.85(Multidisciplinary Sciences)By employing quasi-free -cluster-knockout reactions, we obtained direct experimental evidence for the formation of clusters at the surface of neutron-rich tin isotopes. The observed monotonous decrease of the reaction cross sections with increasing mass number, in excellent agreement with the theoretical prediction, implies a tight interplay between -cluster formation and the neutron skin.
= 32 shell closure below calcium; Low-lying structure of 
ArCort
s, M. L.*; Rodriguez, W.*; Doornenbal, P.*; Obertelli, A.*; Holt, J. D.*; Menndez, J.*; Ogata, Kazuyuki*; Schwenk, A.*; Shimizu, Noritaka*; Simonis, J.*; et al.
Physical Review C, 102(6), p.064320_1 - 064320_9, 2020/12
Times Cited Count：7 Percentile：71.34(Physics, Nuclear)Low-lying excited states in the = 32 isotope Ar were investigated by in-beam -ray spectroscopy following proton- and neutron-knockout, multinucleon removal, and proton inelastic scattering at the RIKEN Radioactive Isotope Beam Factory. The energies of the two previously reported transitions have been confirmed, and five additional states are presented for the first time, including a candidate for a 3 state. The level scheme built using coincidences was compared to shell-model calculations in the 
model space and to 
predictions based on chiral two- and three-nucleon interactions. Theoretical proton- and neutron-knockout cross sections suggest that two of the new transitions correspond to 2
states, while the previously proposed 4
state could also correspond to a 2 state.
F from 
O
?Tang, T. L.*; Uesaka, Tomohiro*; Kawase, Shoichiro; Beaumel, D.*; Dozono, Masanori*; Fujii, Toshihiko*; Fukuda, Naoki*; Fukunaga, Taku*; Galindo-Uribarri, A.*; Hwang, S. H.*; et al.
Physical Review Letters, 124(21), p.212502_1 - 212502_6, 2020/05
Times Cited Count：10 Percentile：74.3(Physics, Multidisciplinary)The structure of a neutron-rich F nucleus is investigated by a quasifree (
) knockout reaction. The sum of spectroscopic factors of 
orbital is found to be 1.0 
0.3. The result shows that the O core of F nucleus significantly differs from a free O nucleus, and the core consists of 35% O
, and 65% excited O. The result shows that the O core of F nucleus significantly differs from a free O nucleus. The result may infer that the addition of the proton considerably changes the neutron structure in F from that in O, which could be a possible mechanism responsible for the oxygen dripline anomaly.
CoLokotko, T.*; Leblond, S.*; Lee, J.*; Doornenbal, P.*; Obertelli, A.*; Poves, A.*; Nowacki, F.*; Ogata, Kazuyuki*; Yoshida, Kazuki; Authelet, G.*; et al.
Physical Review C, 101(3), p.034314_1 - 034314_7, 2020/03
Times Cited Count：6 Percentile：65.07(Physics, Nuclear)The structures of the neutron-rich Co isotopes were investigated via () knockout reactions at the Radioactive Isotope Beam Factory, RIKEN. Level schemes were reconstructed using the 
coincidence technique, with tentative spin-parity assignments based on the measured inclusive and exclusive cross sections. Comparison with shell-model calculations suggests coexistence of spherical and deformed shapes at low excitation energies in the Co isotopes.
energy splitting in odd-K isotopes towards 
Sun, Y. L.*; Obertelli, A.*; Doornenbal, P.*; Barbieri, C.*; Chazono, Yoshiki*; Duguet, T.*; Liu, H. N.*; Navrtil, P.*; Nowacki, F.*; Ogata, Kazuyuki*; et al.
Physics Letters B, 802, p.135215_1 - 135215_7, 2020/03
Times Cited Count：19 Percentile：94.9(Astronomy & Astrophysics)no abstracts in English
= 40 isotones towards 
Ca; First spectroscopy of 
TiCorts, M. L.*; Rodriguez, W.*; Doornenbal, P.*; Obertelli, A.*; Holt, J. D.*; Lenzi, S. M.*; Menndez, J.*; Nowacki, F.*; Ogata, Kazuyuki*; Poves, A.*; et al.
Physics Letters B, 800, p.135071_1 - 135071_7, 2020/01
Times Cited Count：22 Percentile：96.25(Astronomy & Astrophysics)Excited states in the = 40 isotone Ti were populated via the 
V(,)Ti reaction at 200 MeV/nucleon at the Radioactive Isotope Beam Factory and studied using -ray spectroscopy. The energies of the 
and 
transitions, observed here for the first time, indicate a deformed Ti ground state. These energies are increased compared to the neighboring 
Cr and 
Fe isotones, suggesting a small decrease of quadrupole collectivity. The present measurement is well reproduced by large-scale shell-model calculations based on effective interactions, while ab initio and beyond mean-field calculations do not yet reproduce our findings.
,
) reactions in the distorted-wave impulse approximationPhuc, N. T. T.*; Yoshida, Kazuki; Ogata, Kazuyuki*
Physical Review C, 100(6), p.064604_1 - 064604_8, 2019/12
Times Cited Count：6 Percentile：62.36(Physics, Nuclear)Our goal is to investigate the effects of various corrections and uncertainties within the standard distorted-wave impulse approximation (DIWA) formalism on the (,) cross sections. We analyze the (,) and (,) reactions data measured at the R3B/LAND setup at GSI for carbon, nitrogen and oxygen isotopes in the incident energy range of 300-450 MeV/u. Cross sections and reduction factors are calculated by the DWIA method. We have found that including the nonlocality corrections and M
ller factor affects the cross sections considerably. The proton-neutron asymmetry dependence of reduction factors extracted by the DWIA calculation is very weak and consistent with those given by other reaction methods and ab initio structure calculations. They also suggest that some higher-order effects, which is essential for an accurate cross section description at large recoil momentum, is missing in the current DWIA and other reaction models.
