Difference in peripherality of the inclusive and reactions and its implications for a phenomenological reaction model

Nakada, Hibiki*; Nakayama, Shinsuke; Yoshida, Kazuki; Watanabe, Yukinobu*; Ogata, Kazuyuki*

Physical Review C, 110(1), p.014616_1 - 014616_8, 2024/07

https://doi.org/10.1103/PhysRevC.110.014616

Previous studies have revealed the importance of introducing surface correction into a phenomenological model for inclusive and reactions, and these findings have contributed significantly to the improvement of nuclear data evaluation. However, the necessity for the surface correction in an inclusive reaction has hardly been investigated. The energy spectra and their radial distributions for the and reactions are calculated by the one-step semiclassical distorted wave model. The radial distribution of the energy spectra for the reaction is shifted toward the outer region of the nucleus compared to the reaction. Based on this finding, we consider a larger surface correction into a phenomenological model for the reaction than that for the reaction, and calculated values reproduce the experimental spectra well. The peripherality of the reaction is more prominent than that of the reaction. The stronger surface correction thus should be introduced for the reaction than for the reaction.

PIKOE: A Computer program for distorted-wave impulse approximation calculation for proton induced nucleon knockout reactions

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

Computer Physics Communications, 297, p.109058_1 - 109058_16, 2024/04

https://doi.org/10.1016/j.cpc.2023.109058

PIKOE is a Fortran 90 program that calculates triple- and quadruple-differential cross sections, vector analyzing powers, and momentum distributions of reaction residues, for proton-induced nucleon knockout reactions in normal and inverse kinematics. The distorted-wave impulse approximation is adopted, and the distorted waves are calculated quantum mechanically. Kinematics of the reaction particles are treated in a relativistic manner, which gives the proper asymptotics of the three-body scattering wave in the plane-wave limit.

Validation of the Be ground-state molecular structure using Be()He triple differential reaction cross-section measurements

Li, P. J.*; Beaumel, D.*; Lee, J.*; Assi, M.*; Chen, S.*; Franchoo, S.*; Gibelin, J.*; Hammache, F.*; Harada, T.*; Kanada-En'yo, Yoshiko*; et al.

Physical Review Letters, 131(21), p.212501_1 - 212501_7, 2023/11

https://doi.org/10.1103/PhysRevLett.131.212501

The cluster structure of the neutron-rich isotope Be has been probed via the () reaction. The triple differential cross-section was extracted and compared to distorted-wave impulse approximation reaction calculations performed in a microscopic framework using the Tohsaki-Horiuchi-Schuck-Rpke wave function and the wave function deduced from Antisymmetrized Molecular Dynamics calculations. The remarkable agreement between calculated and measured cross-sections in both shape and magnitude validates the description of the Be ground-state as a rather compact nuclear molecule.

Description of the inclusive 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

https://doi.org/10.1103/PhysRevC.108.034603

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 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.

Level structures of Ca cast doubt on a doubly magic 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

https://doi.org/10.1016/j.physletb.2023.138025

Gamma decays were observed in Ca and Ca following quasi-free one-proton knockout reactions from Sc. For Ca, a ray transition was measured to be 1456(12) keV, while for Ca an indication for a transition was observed at 1115(34) keV. Both transitions were tentatively assigned as the decays. A shell-model calculation in a wide model space with a marginally modified effective nucleon-nucleon interaction depicts excellent agreement with experiment for 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 and orbitals, are almost degenerate. This degeneracy precludes the possibility for a doubly magic Ca and potentially drives the dripline of Ca isotopes to Ca or even beyond.

Effective polarization in proton-induced knockout reactions

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

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

https://doi.org/10.1103/PhysRevC.107.054603

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

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

https://doi.org/10.1103/PhysRevC.106.064613

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.

Extended neutron orbital and the shell closure in 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

https://doi.org/10.1103/PhysRevLett.129.262501

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.

Theoretical study of deuteron-induced reactions in the nuclear data field

Nakayama, Shinsuke; Iwamoto, Osamu; Watanabe, Yukinobu*; Ogata, Kazuyuki*

Few-Body Systems, 63(1), p.4_1 - 4_6, 2022/03

https://doi.org/10.1007/s00601-021-01712-2

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.

Investigation of the ground-state spin inversion in the neutron-rich Cl isotopes

Linh, B. D.*; Corsi, A.*; Gillibert, A.*; Obertelli, A.*; Doornenbal, P.*; Barbieri, C.*; Chen, S.*; Chung, L. X.*; Duguet, T.*; Gmez-Ramos, M.*; et al.

Physical Review C, 104(4), p.044331_1 - 044331_16, 2021/10

AA2021-0468.pdf:1.29MB

https://doi.org/10.1103/PhysRevC.104.044331

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