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Journal Articles

Systematic analysis of the nuclear absorption effect on the cross section of the knockout reaction

Shim, S.-I.*; Yoshida, Kazuki; Ogata, Kazuyuki*

Journal of the Physical Society of Japan, 92(9), p.094201_1 - 094201_8, 2023/09

We systematically investigate the absorption effects on the cross sections of the nucleon and alpha knockout reactions. To do this, we calculate the ratio of the cross sections of the distorted-wave impulse approximation and plane-wave impulse approximation and examine its dependence on the mass number and single-particle orbital of the knocked-out particles.

Journal Articles

Description of the inclusive $$(d,d'x)$$ reaction with the semiclassical distorted-wave model

Nakada, Hibiki*; Yoshida, Kazuki; Ogata, Kazuyuki*

Physical Review C, 108(3), p.034603_1 - 034603_8, 2023/09

The description of deuteron-induced inclusive reactions has been an important subject in direct nuclear reaction studies and nuclear data science. For proton-induced inclusive processes, the semiclassical distorted wave model (SCDW) is one of the most successful models based on quantum mechanics. We improve SCDW for deuteron-induced inclusive processes. The changes in the kinematics due to the distortion effect, the refraction effect, is taken into account by the local semiclassical approximation. The calculated cross section of $$(d,d'x)$$ reasonably reproduce experimental data in the small energy-transfer region and at forward and middle angles with some exceptions. The angular distributions of the cross section are improved by including the refraction effect. The effect on the cross section is significant compared to that on the proton-induced inclusive process because of the stronger distortion effect on the deuteron.

Journal Articles

Level structures of $$^{56,58}$$Ca cast doubt on a doubly magic $$^{60}$$Ca

Chen, S.*; Browne, F.*; Doornenbal, P.*; Lee, J.*; Obertelli, A.*; Tsunoda, Yusuke*; Otsuka, Takaharu*; Chazono, Yoshiki*; Hagen, G.*; Holt, J. D.*; et al.

Physics Letters B, 843, p.138025_1 - 138025_7, 2023/08

Gamma decays were observed in $$^{56}$$Ca and $$^{58}$$Ca following quasi-free one-proton knockout reactions from $$^{57,59}$$Sc. For $$^{56}$$Ca, a $$gamma$$ ray transition was measured to be 1456(12) keV, while for $$^{58}$$Ca an indication for a transition was observed at 1115(34) keV. Both transitions were tentatively assigned as the $$2^{+}_{1} rightarrow 0^{+}_{gs}$$ decays. A shell-model calculation in a wide model space with a marginally modified effective nucleon-nucleon interaction depicts excellent agreement with experiment for $$2^{+}_{1}$$ level energies, two-neutron separation energies, and reaction cross sections, corroborating the formation of a new nuclear shell above the N = 34 shell. Its constituents, the $$0_{f5/2}$$ and $$0_{g9/2}$$ orbitals, are almost degenerate. This degeneracy precludes the possibility for a doubly magic $$^{60}$$Ca and potentially drives the dripline of Ca isotopes to $$^{70}$$Ca or even beyond.

Journal Articles

Intruder configurations in $$^{29}$$Ne at the transition into the island of inversion; Detailed structure study of $$^{28}$$Ne

Wang, H.*; Yasuda, Masahiro*; Kondo, Yosuke*; Nakamura, Takashi*; Tostevin, J. A.*; Ogata, Kazuyuki*; Otsuka, Takaharu*; Poves, A.*; Shimizu, Noritaka*; Yoshida, Kazuki; et al.

Physics Letters B, 843, p.138038_1 - 138038_9, 2023/08

Detailed $$gamma$$-ray spectroscopy of the exotic neon isotope $$^{28}$$Ne has been performed using the one-neutron removal reaction from $$^{29}$$Ne. Based on an analysis of parallel momentum distributions, a level scheme with spin-parity assignments has been constructed for $$^{28}$$Ne and the negative-parity states are identified for the first time. The measured partial cross sections and momentum distributions reveal a significant intruder p-wave strength providing evidence of the breakdown of the N = 20 and N = 28 shell gaps. Only a weak, possible f-wave strength was observed to bound final states. Large-scale shell-model calculations with different effective interactions do not reproduce the large p-wave and small f-wave strength observed experimentally, indicating an ongoing challenge for a complete theoretical description of the transition into the island of inversion along the Ne isotopic chain.

Journal Articles

Exploring spin-polarization in Bi-based high-$$T_c$$ cuprates

Iwasawa, Hideaki*; Sumida, Kazuki; Ishida, Shigeyuki*; Le F$`e$vre, P.*; Bertran, F.*; Yoshida, Yoshiyuki*; Eisaki, Hiroshi*; Santander-Syro, A.*; Okuda, Taichi*

Scientific Reports (Internet), 13, p.13451_1 - 13451_7, 2023/08

Journal Articles

Effective polarization in proton-induced $$alpha$$ knockout reactions

Edagawa, Tomoatsu*; Yoshida, Kazuki; Chazono, Yoshiki*; Ogata, Kazuyuki*

Physical Review C, 107(5), p.054603_1 - 054603_7, 2023/05

 Times Cited Count:0 Percentile:87.83(Physics, Nuclear)

The effective polarization of the residual nucleus in the proton-induced $$alpha$$ knockout reaction is investigated within the distorted wave impulse approximation framework. The strong absorption of the emitted $$alpha$$ particle results in strong selectivity on the reaction "position" depending on the third component of the single-particle orbital angular momentum of the $$alpha$$ particle inside a nucleus, hence on the spin direction of the reaction residue.

Journal Articles

Multiple mechanisms in proton-induced nucleon removal at $$sim$$100 MeV/nucleon

Pohl, T.*; Sun, Y. L.*; Obertelli, A.*; Lee, J.*; G$'o$mez-Ramos, M.*; Ogata, Kazuyuki*; Yoshida, Kazuki; Cai, B. S.*; Yuan, C. X.*; Brown, B. A.*; et al.

Physical Review Letters, 130(17), p.172501_1 - 172501_8, 2023/04

 Times Cited Count:2 Percentile:90.46(Physics, Multidisciplinary)

We report on the first proton-induced single proton- and neutron-removal reactions from the neutron deficient $$^{14}$$O nucleus with large Fermi-surface asymmetry at $$sim$$100 MeV/nucleon. Our results provide the first quantitative contributions of multiple reaction mechanisms including the quasifree knockout, inelastic scattering, and nucleon transfer processes. It is shown that the inelastic scattering and nucleon transfer, usually neglected at such energy regime, contribute about 50% and 30% to the loosely bound proton and deeply bound neutron removal, respectively.

Journal Articles

"Southwestern" boundary of the $$N = 40$$ island of inversion; First study of low-lying bound excited states in $$^{59}$$V and $$^{61}$$V

Elekes, Z.*; Juh$'a$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:0 Percentile:0.02(Physics, Nuclear)

The low-lying level structure of $$^{59}$$V and $$^{61}$$V was investigated for the first time. The neutron knockout reaction and inelastic proton scattering were applied for $$^{61}$$V while the neutron knock-out reaction provided the data for $$^{59}$$V. Four and five new transitions were determined for $$^{59}$$V and $$^{61}$$V, respectively. Based on the comparison to our shell-model calculations using the Lenzi-Nowacki-Poves-Sieja (LNPS) interaction, three of the observed $$gamma$$ 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 ($$p$$,$$p'$$) excitation cross sections for $$^{61}$$V were analyzed by the coupled-channels formalism assuming quadrupole plus hexadecapole deformations. Due to the role of the hexadecapole deformation, $$^{61}$$V could not be unambiguously placed on the island of inversion.

Journal Articles

Importance of deuteron breakup in the deuteron knockout reaction

Chazono, Yoshiki*; Yoshida, Kazuki; Ogata, Kazuyuki*

Physical Review C, 106(6), p.064613_1 - 064613_10, 2022/12

 Times Cited Count:0 Percentile:34.54(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.

Journal Articles

Extended $$p_{3/2}$$ neutron orbital and the $$N = 32$$ shell closure in $$^{52}$$Ca

Enciu, 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:29.72(Physics, Multidisciplinary)

The one-neutron knockout from $$^{52}$$Ca was performed at $$sim$$230 MeV/nucleon combined with prompt $$gamma$$ spectroscopy. The momentum distributions corresponding to the removal of $$1f_{7/2}$$ and $$2p_{3/2}$$ neutrons were measured. The cross sections are consistent with a shell closure at the neutron number $$N = 32$$, found as strong as at $$N = 28$$ and $$N = 34$$ 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 $$1_{f7/2}$$ and $$2p_{3/2}$$ 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 $$2p_{3/2}$$ orbital in neutron-rich Ca isotopes is responsible for the unexpected linear increase of the charge radius with the neutron number.

Journal Articles

$$alpha$$ knockout reaction as a new probe for $$alpha$$ formation in $$alpha$$-decay nuclei

Yoshida, Kazuki; Tanaka, Junki*

Physical Review C, 106(1), p.014621_1 - 014621_6, 2022/07

 Times Cited Count:1 Percentile:68.81(Physics, Nuclear)

Alternative to the $$alpha$$ decay lifetime measurement, we propose the proton-induced $$alpha$$ knockout reaction, ($$p$$,$$palpha$$), as a new probe for the surface $$alpha$$ formation probability of $$alpha$$ decay nuclei. $$^{210,212}$$Po($$p$$,$$palpha$$)$$^{206,208}$$Pb reaction is described by the distorted-wave impulse approximation framework. It is shown that the $$^{212}$$Po/$$^{210}$$Po ratio of the $$alpha$$ knockout cross sections agree with that of the surface $$alpha$$ formation probabilities determined by the lifetime measurements. The result implies that the ($$p$$,$$palpha$$) cross section is a direct probe for the surface $$alpha$$ formation probability, which is an essential quantity to lead us to a complete understanding of the $$alpha$$ decay phenomena.

Journal Articles

A First glimpse at the shell structure beyond $$^{54}$$Ca; Spectroscopy of $$^{55}$$K, $$^{55}$$Ca, and $$^{57}$$Ca

Koiwai, Takuma*; Wimmer, K.*; Doornenbal, P.*; Obertelli, A.*; Barbieri, C.*; Duguet, T.*; Holt, J. D.*; Miyagi, Takayuki*; Navr$'a$til, P.*; Ogata, Kazuyuki*; et al.

Physics Letters B, 827, p.136953_1 - 136953_7, 2022/04

 Times Cited Count:2 Percentile:54.36(Astronomy & Astrophysics)

no abstracts in English

Journal Articles

First application of the dispersive optical model to ($$p$$,$$2p$$) reaction analysis within the distorted-wave impulse approximation framework

Yoshida, Kazuki; Atkinson, M. C.*; Ogata, Kazuyuki*; Dickhoff, W. H.*

Physical Review C, 105(1), p.014622_1 - 014622_7, 2022/01

 Times Cited Count:1 Percentile:34.54(Physics, Nuclear)

We apply the dispersive optical model (DOM) wave functions to the traditional ($$p$$,$$2p$$) analysis and investigate the consistency of the DOM spectroscopic factor that describes the ($$e$$,$$e'p$$) cross section with the result of the ($$p$$,$$2p$$) analysis. DOM + distorted wave impulse approximation analysis on $$^{40}$$Ca($$p$$,$$2p$$)$$^{39}$$K data generates a proton $$0d_{3/2}$$ spectroscopic factor of 0.560, which is meaningfully smaller than the DOM value of 0.71 shown to be consistent with the ($$e$$,$$e'p$$) analysis. The inconsistency in the spectroscopic factor suggests there is urgent need for improving the description of $$p$$-$$p$$ scattering in a nucleus.

Journal Articles

Bound state properties studied by the knockout reaction

Yoshida, Kazuki

Few-Body Systems, 62(2), p.28_1 - 28_7, 2021/06

 Times Cited Count:1 Percentile:31.34(Physics, Multidisciplinary)

Atomic nucleus is a quantum many-body system consisting of protons and neutrons. Nevertheless, it is known that their characteristics can be well described and understood by the few-body picture. One of such pictures is the single-particle motion of a nucleon in a mean-field potential made by all nucleons. Another one is the clustering phenomenon, $$alpha$$ clustering for example. One of the powerful probes for such states of a nucleus is the nucleon and cluster knockout reactions. In this paper, I overview how these states can be probed by the knockout reaction and discuss the present status and the future perspectives of this research field.

Journal Articles

First spectroscopic study of $$^{63}$$V at the $$N = 40$$ island of inversion

Juh$'a$sz, M. M.*; Yoshida, Kazuki; 77 of others*

Physical Review C, 103(6), p.064308_1 - 064308_9, 2021/06

 Times Cited Count:2 Percentile:35.95(Physics, Nuclear)

The level structure of $$^{63}$$V was studied for the first time by the inelastic proton scattering and the proton knock-out reaction. The comparison of the newly observed $$gamma$$-ray transitions at 696(8) keV and 889(16) keV with our shell-model calculations using the Lenzi-Nowacki-Poves-Sieja interaction established two excited states proposed to be the first 11/2$$^{-}$$ and 9/2$$^{-}$$ levels. The ($$p$$,$$p'$$) excitation cross sections were analyzed by the coupled channel formalism assuming pure quadrupole as well as quadrupole+hexadecapole deformations. This resulted in large deformation parameters placing $$^{63}$$V in the island of inversion located below $$^{68}$$Ni.

Journal Articles

Pairing forces govern population of doubly magic $$^{54}$$Ca from direct reactions

Browne, 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:8 Percentile:70.49(Physics, Multidisciplinary)

Direct proton-knockout reactions of $$^{55}$$Sc were studied at the RIKEN Radioactive Isotope Beam Factory. Populated states of $$^{54}$$Ca were investigated through $$gamma$$-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 $$^{55}$$Sc, valence proton removals populated predominantly the ground-state of $$^{54}$$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.

Journal Articles

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

Taniguchi, 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:8 Percentile:83.54(Physics, Nuclear)

Based on the $$^{48}$$Ti($$p$$,$$palpha$$)$$^{44}$$Ca reaction analysis, this study reports that $$alpha$$-particle formation in the medium-mass $$^{48}$$Ti nucleus is pronounced more compared to that expected through mean-field approximations. Moreover, the estimated average distance between the $$alpha$$ particle and residue equals approximately 4.5 fm. This result poses a challenge to describe the four nucleon correlations using microscopic nuclear models.

Journal Articles

First spectroscopic study of $$^{51}$$Ar by the ($$p$$,2$$p$$) reaction

Juh$'a$sz, 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:3 Percentile:48.27(Astronomy & Astrophysics)

The nuclear structure of $$^{51}$$Ar was studied by the ($$p$$,2$$p$$) reaction using $$gamma$$-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 $$^{51}$$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.

Journal Articles

Morphological reproductive characteristics of testes and fertilization capacity of cryopreserved sperm after the Fukushima accident in raccoon (${it Procyon lotor}$)

Komatsu, Kazuki*; Iwasaki, Tsugumi*; Murata, Kosuke*; Yamashiro, Hideaki*; Goh, V. S. T.*; Nakayama, Ryo*; Fujishima, Yohei*; Ono, Takumi*; Kino, Yasushi*; Shimizu, Yoshinaka*; et al.

Reproduction in Domestic Animals, 56(3), p.484 - 497, 2021/03

 Times Cited Count:9 Percentile:88.06(Agriculture, Dairy & Animal Science)

We have established an archive system of livestock and wild animals from the surrounding ex-evacuation zone. Wildlife within the alert zone have been exposed to low-dose-rate (LDR) radiation for a long and continuous time. In this study, we analysed the morphological characteristics of the testes and in vitro fertilization (IVF) capacity of cryopreserved sperm of raccoons from the ex-evacuation zone of the FDNPP accident. This study revealed that the chronic and LDR radiation exposure associated with the FDNPP accident had no adverse effect on the reproductive characteristics and functions of male raccoons.

Journal Articles

Proton-induced deuteron knockout reaction as a probe of an isoscalar proton-neutron pair in nuclei

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:35.95(Physics, Nuclear)

The isoscalar $$pn$$ pair is expected to emerge in nuclei. We aim to clarify the correspondence between the $$pn$$ pairing strength in many-body calculation and the cross section of proton-induced deuteron knockout ($$p$$, $$pd$$) reaction on $$^{16}$$O. The radial wave function of the isoscalar $$pn$$ pair with respect to the center of $$^{16}$$O is calculated with the energy density functional (EDF) approach and is implemented in the distorted wave impulse approximation framework. The $$pn$$ pairing strength $$V_0$$ in the EDF calculation is varied and the corresponding change in the cross section is investigated. A clear $$V_0$$ dependence of the cross section is found. The nuclear distortion is found to make the $$V_0$$ dependence stronger. Because of the clear $$V_0$$-coross section correspondence, the ($$p$$, $$pd$$) reaction will be a promising probe for the isoscalar $$pn$$ pair in nuclei. For quantitative discussion, further modification of the description of the reaction process will be necessary.

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