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1. Production of neutron-rich nuclei in the vicinity of 78Ni: Fragmentation reactions of unstable 81Ga and 82Ge beams

Author

X.H. Sun, H. Wang, K. Yoneda, N. Aoi, H. Baba, P. Bednarczyk, Zs. Dombrádi, P. Doornenbal, Zs. Fülöp, S. Go, T. Hashimoto, E. Ideguchi, K. Kobayashi, Y. Kondo, J. Lee, H.N. Liu, W.P. Liu, J.L. Lou, M. Matsushita, R. Minakata, T. Motobayashi, D. Nishimura, H. Otsu, H. Sakurai, Y. Shiga, Y.P. Shen, D. Sohler, D. Steppenbeck, Y.L. Sun, S. Takeuchi, A. Tamii, R. Tanaka, Z.Y. Tian, Zs. Vajta, T. Yamamoto, X.F. Yang, Z.H. Yang, Y.L. Ye, R. Yokoyama, and J. Zenihiro

Subjects
Projectile fragmentation of unstable nuclei, Production of neutron-rich nuclei, Two-step scheme, Physics, QC1-999
Abstract

The fragmentation reactions of neutron-rich unstable nuclei 81Ga and 82Ge at 250 MeV/nucleon have been studied in order to search the optimal mean for the production of very neutron-rich nuclei in the vicinity of 78Ni. The newly measured cross sections were compared with various calculations, showing a good agreement with EPAX3.01. The present work provides experimental insights into the two-step scheme—fragmentation following fission—as a method to produce very neutron-rich nuclei through a combination of ISOL and fragmentation of post-accelerated beams of unstable nuclei. Our results enable an evaluation of the potential of the two-step scheme in the production of very neutron-rich nuclei for the 78Ni region. The two-step scheme using fragmentation of a post-accelerated 81Ga beam could be an option to produce neutron-rich nuclei around 78Ni when the 81Ga beam intensity reaches 1.0×108 pps, compared to the one-step scheme with fission of 238U.

Published
2024
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2. Evolution of the two-neutron configuration from 11Li to 13Li

Author

P. André, A. Corsi, A. Revel, Y. Kubota, J. Casal, K. Fossez, J. Gómez-Camacho, G. Authelet, H. Baba, C. Caesar, D. Calvet, A. Delbart, M. Dozono, J. Feng, F. Flavigny, J.-M. Gheller, J. Gibelin, A. Giganon, A. Gillibert, K. Hasegawa, T. Isobe, Y. Kanaya, S. Kawakami, D. Kim, Y. Kiyokawa, M. Kobayashi, N. Kobayashi, T. Kobayashi, Y. Kondo, Z. Korkulu, S. Koyama, V. Lapoux, Y. Maeda, F.M. Marqués, T. Motobayashi, T. Miyazaki, T. Nakamura, N. Nakatsuka, Y. Nishio, A. Obertelli, A. Ohkura, N.A. Orr, S. Ota, H. Otsu, T. Ozaki, V. Panin, S. Paschalis, E.C. Pollacco, S. Reichert, J.-Y. Rousse, A.T. Saito, S. Sakaguchi, M. Sako, C. Santamaria, M. Sasano, H. Sato, M. Shikata, Y. Shimizu, Y. Shindo, L. Stuhl, T. Sumikama, Y.L. Sun, M. Tabata, Y. Togano, J. Tsubota, T. Uesaka, Z.H. Yang, J. Yasuda, K. Yoneda, and J. Zenihiro

Subjects
Quasi-free scattering, Three-body model, Dineutron decay, Physics, QC1-999
Abstract

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.

Published
2024
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3. Spectroscopy of deeply bound orbitals in neutron-rich Ca isotopes

Author

P.J. Li, J. Lee, P. Doornenbal, S. Chen, S. Wang, A. Obertelli, Y. Chazono, J.D. Holt, B.S. Hu, K. Ogata, Y. Utsuno, K. Yoshida, N.L. Achouri, H. Baba, F. Browne, D. Calvet, F. Château, N. Chiga, A. Corsi, M.L. Cortés, A. Delbart, J.-M. Gheller, A. Giganon, A. Gillibert, C. Hilaire, T. Isobe, T. Kobayashi, Y. Kubota, V. Lapoux, H.N. Liu, T. Motobayashi, I. Murray, H. Otsu, V. Panin, N. Paul, W. Rodriguez, H. Sakurai, M. Sasano, D. Steppenbeck, L. Stuhl, Y.L. Sun, Y. Togano, T. Uesaka, K. Wimmer, K. Yoneda, O. Aktas, T. Aumann, K. Boretzky, C. Caesar, L.X. Chung, F. Flavigny, S. Franchoo, I. Gasparic, R.-B. Gerst, J. Gibelin, K.I. Hahn, J. Kahlbow, D. Kim, T. Koiwai, Y. Kondo, D. Körper, P. Koseoglou, C. Lehr, B.D. Linh, T. Lokotko, M. MacCormick, K. Miki, K. Moschner, T. Nakamura, S.Y. Park, D. Rossi, E. Sahin, F. Schindler, H. Simon, P.-A. Söderström, D. Sohler, S. Takeuchi, H. Toernqvist, J. Tscheuschner, V. Vaquero, V. Wagner, V. Werner, X. Xu, H. Yamada, D. Yan, Z. Yang, M. Yasuda, and L. Zanetti

Subjects
Unbound states, Knockout reaction, Single-particle strength, Shell evolution, Physics, QC1-999
Abstract

The calcium isotopes are an ideal system to investigate the evolution of shell structure and magic numbers. Although the properties of surface nucleons in calcium have been well studied, probing the structure of deeply bound nucleons remains a challenge. Here, we report on the first measurement of unbound states in 53Ca and 55Ca, populated from 54,56Ca(p,pn) reactions at a beam energy of around 216 MeV/nucleon at the RIKEN Radioactive Isotopes Beam Factory. The resonance properties, partial cross sections, and momentum distributions of these unbound states were analyzed. Orbital angular momentum l assignments were extracted from momentum distributions based on calculations using the distorted wave impulse approximation (DWIA) reaction model. The resonances at excitation energies of 5516(41)keV in 53Ca and 6000(250)keV in 55Ca indicate a significant l =3 component, providing the first experimental evidence for the ν0f7/2 single-particle strength of unbound hole states in the neutron-rich Ca isotopes. The observed excitation energies and cross-sections point towards extremely localized and well separated strength distributions, with some fragmentation for the ν0f7/2 orbital in 55Ca. These results are in good agreement with predictions from shell-model calculations using the effective GXPF1Bs interaction and ab initio calculations and diverge markedly from the experimental distributions in the nickel isotones at Z=28.

Published
2024
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4. Shape coexistence in 66Se

Author

Z. Elekes, V. Panin, T.R. Rodríguez, K. Sieja, D.S. Ahn, A. Al-Adili, H. Baba, A.I. Stefanescu, K.J. Cook, Cs. Dósa, N. Fukuda, J. Gao, J. Gibelin, K.I. Hahn, Z. Halász, S.W. Huang, T. Isobe, M.M. Juhász, D. Kim, T. Kobayashi, Y. Kondo, Z. Korkulu, A. Kurihara, I. Kuti, H. Miki, K. Miki, T. Motobayashi, H. Otsu, A. Saastamoinen, M. Sasano, H. Sato, T. Shimada, Y. Shimizu, L.G. Sobotka, I. Stefanescu, L. Stuhl, H. Suzuki, H. Takeda, Y. Togano, T. Tomai, L. Trache, D. Tudor, T. Uesaka, Y. Utsuki, H. Wang, A. Yasuda, K. Yoneda, and Y. Yoshitome

Subjects
Neutron knock-out reaction, γ-ray spectroscopy, Nuclear structure, Shape coexistence, Physics, QC1-999
Abstract

The nuclear structure of 66Se, nucleus beyond the N=Z line on the proton-rich side of the valley of stability, was investigated by the neutron knock-out reaction 67Se(12C,X)66Se using a 12C target. The analysis of the singles spectrum of the γ-rays emitted during the de-excitation of the populated low-lying excited states revealed two previously detected (927(4) keV, 1460(32) keV) and three new (744(6) keV, 1210(17) keV, 1661(23) keV) transitions. The 744-keV, the 1210-keV, and the 1460-keV transitions were found to be in coincidence with the one at 927 keV. The spectrum coincident with the 927-keV transition showed a further possible transition at 299(35) keV, which was obscured by significant atomic background in the singles spectrum. This transition might correspond to a peak previously reported at 273(5) keV that could not be assigned to 66Se unambiguously. Based on a comparison of the experimental data to theoretical calculations, four new excited states are proposed which suggest that 66Se exhibits shape coexistence.

Published
2023
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5. Level structures of 56,58Ca cast doubt on a doubly magic 60Ca

Author

S. Chen, F. Browne, P. Doornenbal, J. Lee, A. Obertelli, Y. Tsunoda, T. Otsuka, Y. Chazono, G. Hagen, J.D. Holt, G.R. Jansen, K. Ogata, N. Shimizu, Y. Utsuno, K. Yoshida, N.L. Achouri, H. Baba, D. Calvet, F. Château, N. Chiga, A. Corsi, M.L. Cortés, A. Delbart, J.-M. Gheller, A. Giganon, A. Gillibert, C. Hilaire, T. Isobe, T. Kobayashi, Y. Kubota, V. Lapoux, H.N. Liu, T. Motobayashi, I. Murray, H. Otsu, V. Panin, N. Paul, W. Rodriguez, H. Sakurai, M. Sasano, D. Steppenbeck, L. Stuhl, Y.L. Sun, Y. Togano, T. Uesaka, K. Wimmer, K. Yoneda, O. Aktas, T. Aumann, L.X. Chung, F. Flavigny, S. Franchoo, I. Gasparic, R.-B. Gerst, J. Gibelin, K.I. Hahn, D. Kim, T. Koiwai, Y. Kondo, P. Koseoglou, C. Lehr, B.D. Linh, T. Lokotko, M. MacCormick, K. Moschner, T. Nakamura, S.Y. Park, D. Rossi, E. Sahin, P.-A. Söderström, D. Sohler, S. Takeuchi, H. Törnqvist, V. Vaquero, V. Wagner, S. Wang, V. Werner, X. Xu, H. Yamada, D. Yan, Z. Yang, M. Yasuda, and L. Zanetti

Subjects
Shell evolution, γ Ray spectroscopy, Physics, QC1-999
Abstract

Gamma decays were observed in 56Ca and 58Ca following quasi-free one-proton knockout reactions from 57,59Sc beams at ≈200 MeV/nucleon. For 56Ca, a γ ray transition was measured to be 1456(12) keV, while for 58Ca an indication for a transition was observed at 1115(34) keV. Both transitions were tentatively assigned as the 21+→0gs+ decays, and were compared to results from ab initio and conventional shell-model approaches. A shell-model calculation in a wide model space with a marginally modified effective nucleon-nucleon interaction depicts excellent agreement with experiment for 21+ 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 0f5/2 and 0g9/2 orbitals, are almost degenerate. This degeneracy precludes the possibility for a doubly magic 60Ca and potentially drives the dripline of Ca isotopes to 70Ca or even beyond.

Published
2023
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6. Searching for universality of dineutron correlation at the surface of Borromean nuclei

Author

A. Corsi, Y. Kubota, J. Casal, M. Gómez-Ramos, A.M. Moro, G. Authelet, H. Baba, C. Caesar, D. Calvet, A. Delbart, M. Dozono, J. Feng, F. Flavigny, J.-M. Gheller, J. Gibelin, A. Giganon, A. Gillibert, K. Hasegawa, T. Isobe, Y. Kanaya, S. Kawakami, D. Kim, Y. Kiyokawa, M. Kobayashi, N. Kobayashi, T. Kobayashi, Y. Kondo, Z. Korkulu, S. Koyama, V. Lapoux, Y. Maeda, F.M. Marqués, T. Motobayashi, T. Miyazaki, T. Nakamura, N. Nakatsuka, Y. Nishio, A. Obertelli, A. Ohkura, N.A. Orr, S. Ota, H. Otsu, T. Ozaki, V. Panin, S. Paschalis, E.C. Pollacco, S. Reichert, J.-Y. Rousse, A.T. Saito, S. Sakaguchi, M. Sako, C. Santamaria, M. Sasano, H. Sato, M. Shikata, Y. Shimizu, Y. Shindo, L. Stuhl, T. Sumikama, Y.L. Sun, M. Tabata, Y. Togano, J. Tsubota, T. Uesaka, Z.H. Yang, J. Yasuda, K. Yoneda, and J. Zenihiro

Subjects
Quasi-free scattering, Borromean nuclei, Three-body model, Jacobi coordinates, Dineutron, Physics, QC1-999
Abstract

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.

Published
2023
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7. Unbound states in 17C and p-sd shell-model interactions

Author

S. Kim, J.W. Hwang, Y. Satou, N.A. Orr, T. Nakamura, Y. Kondo, J. Gibelin, N.L. Achouri, T. Aumann, H. Baba, F. Delaunay, P. Doornenbal, N. Fukuda, N. Inabe, T. Isobe, D. Kameda, D. Kanno, N. Kobayashi, T. Kobayashi, T. Kubo, S. Leblond, J. Lee, F.M. Marqués, R. Minakata, T. Motobayashi, D. Murai, T. Murakami, K. Muto, T. Nakashima, N. Nakatsuka, A. Navin, S. Nishi, S. Ogoshi, H. Otsu, H. Sato, Y. Shimizu, H. Suzuki, K. Takahashi, H. Takeda, S. Takeuchi, R. Tanaka, Y. Togano, A.G. Tuff, M. Vandebrouck, and K. Yoneda

Subjects
One-neutron removal reaction, Neutron-rich carbon isotopes, Cross-shell states, Shell-model Hamiltonian, Physics, QC1-999
Abstract

Unbound states in C17 were investigated via one-neutron removal from a C18 beam at an energy of 245 MeV/nucleon on a carbon target. The energy spectrum of C17, above the single-neutron decay threshold, was reconstructed using invariant mass spectroscopy from the measured momenta of the C16 fragment and neutron, and was found to exhibit resonances at Er=0.52(2), 0.77(2), 1.36(1), 1.91(1), 2.22(3) and 3.20(1) MeV. The resonance at Er=0.77(2) MeV [Ex=1.51(3) MeV] was provisionally assigned as the second 5/2+ state. The two resonances at Er=1.91(1) and 3.20(1) MeV [Ex=2.65(2) and 3.94(2) MeV] were identified, through comparison of the energies, cross sections and momentum distributions with shell-model and eikonal reaction calculations, as p-shell hole states with spin-parities 1/21− and 3/21−, respectively. A detailed comparison was made with the results obtained using a range of shell-model interactions. The YSOX shell-model Hamiltonian, the cross-shell part of which is based on the monopole-based universal interaction, was found to provide a very good description of the present results and those for the neighbouring odd-A carbon isotopes – in particular for the negative parity cross-shell states.

Published
2023
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8. A first glimpse at the shell structure beyond 54Ca: Spectroscopy of 55K, 55Ca, and 57Ca

Author

T. Koiwai, K. Wimmer, P. Doornenbal, A. Obertelli, C. Barbieri, T. Duguet, J.D. Holt, T. Miyagi, P. Navrátil, K. Ogata, N. Shimizu, V. Somà, Y. Utsuno, K. Yoshida, N.L. Achouri, H. Baba, F. Browne, D. Calvet, F. Château, S. Chen, N. Chiga, A. Corsi, M.L. Cortés, A. Delbart, J.-M. Gheller, A. Giganon, A. Gillibert, C. Hilaire, T. Isobe, T. Kobayashi, Y. Kubota, V. Lapoux, H.N. Liu, T. Motobayashi, I. Murray, H. Otsu, V. Panin, N. Paul, W. Rodriguez, H. Sakurai, M. Sasano, D. Steppenbeck, L. Stuhl, Y.L. Sun, Y. Togano, T. Uesaka, K. Yoneda, O. Aktas, T. Aumann, L.X. Chung, F. Flavigny, S. Franchoo, I. Gasparic, R.-B. Gerst, J. Gibelin, K.I. Hahn, D. Kim, Y. Kondo, P. Koseoglou, J. Lee, C. Lehr, B.D. Linh, T. Lokotko, M. MacCormick, K. Moschner, T. Nakamura, S.Y. Park, D. Rossi, E. Sahin, P.-A. Söderström, D. Sohler, S. Takeuchi, H. Toernqvist, V. Vaquero, V. Wagner, S. Wang, V. Werner, X. Xu, H. Yamada, D. Yan, Z. Yang, M. Yasuda, and L. Zanetti

Subjects
Radioactive beams, γ-ray spectroscopy, Shell evolution, Physics, QC1-999
Abstract

States in the N=35 and 37 isotopes 55,57Ca have been populated by direct proton-induced nucleon removal reactions from 56,58Sc and 56Ca beams at the RIBF. In addition, the (p,2p) quasi-free single-proton removal reaction from 56Ca was studied. Excited states in 55K, 55Ca, and 57Ca were established for the first time via in-beam γ-ray spectroscopy. Results for the proton and neutron removal reactions from 56Ca to states in 55K and 55Ca for the level energies, excited state lifetimes, and exclusive cross sections agree well with state-of-the-art theoretical calculations using different approaches. The observation of a short-lived state in 57Ca suggests a transition in the calcium isotopic chain from single-particle dominated states at N=35 to collective excitations at N=37.

Published
2022
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9. Inclusive cross sections for one- and multi-nucleon removal from Sn, Sb, and Te projectiles beyond the N = 82 shell closure

Author

V. Vaquero, A. Jungclaus, J.L. Rodríguez-Sánchez, J.A. Tostevin, P. Doornenbal, K. Wimmer, S. Chen, E. Nácher, E. Sahin, Y. Shiga, D. Steppenbeck, R. Taniuchi, Z.Y. Xu, T. Ando, H. Baba, F.L. Bello Garrote, S. Franchoo, A. Gargano, K. Hadynska-Klek, A. Kusoglu, J. Liu, T. Lokotko, S. Momiyama, T. Motobayashi, S. Nagamine, N. Nakatsuka, M. Niikura, R. Orlandi, T. Saito, H. Sakurai, P.A. Söderström, G.M. Tveten, Zs. Vajta, and M. Yalcinkaya

Subjects
Physics, QC1-999
Abstract

Inclusive one- and multi-nucleon removal cross sections have been measured for several Sn, Sb and Te isotopes just beyond the N=82 neutron shell closure. The beams were produced in the projectile fission of a 238U beam at the Radioactive Isotope Beam Factory at RIKEN. The experimental cross sections are compared to predictions from the most recent version of the Liege intranuclear cascade model. Although the overall agreement is good, severe discrepancies are observed for the cases of one- and two-neutron removal from 134Sn and 135Sb projectiles and one-proton knockout from all measured N=84 isotones. These discrepancies, as well as the relevance of quasi-elastic reaction channels to the one-neutron removal cross sections, are discussed. In addition, the measured inclusive one-proton knockout cross section for the semi-magic 134Sn projectile is compared to eikonal direct reaction theory calculations to assess if the suppression factors to these calculated cross sections, deduced from data on reactions of lighter projectile nuclei, are also applicable to heavy nuclei. Keywords: Inclusive knockout cross sections, Intranuclear cascade model, Eikonal reaction theory

Published
2019
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10. Discovery of 68Br in secondary reactions of radioactive beams

Author

K. Wimmer, P. Doornenbal, W. Korten, P. Aguilera, A. Algora, T. Ando, T. Arici, H. Baba, B. Blank, A. Boso, S. Chen, A. Corsi, P. Davies, G. de Angelis, G. de France, D.T. Doherty, J. Gerl, R. Gernhäuser, D.G. Jenkins, S. Koyama, T. Motobayashi, S. Nagamine, M. Niikura, A. Obertelli, D. Lubos, B. Rubio, E. Sahin, T.Y. Saito, H. Sakurai, L. Sinclair, D. Steppenbeck, R. Taniuchi, R. Wadsworth, and M. Zielinska

Subjects
Physics, QC1-999
Abstract

The proton-rich isotope 68Br was discovered in secondary fragmentation reactions of fast radioactive beams. Proton-rich secondary beams of 70,71,72Kr and 70Br, produced at the RIKEN Nishina Center and identified by the BigRIPS fragment separator, impinged on a secondary 9Be target. Unambiguous particle identification behind the secondary target was achieved with the ZeroDegree spectrometer. Based on the expected direct production cross sections from neighboring isotopes, the lifetime of the ground or long-lived isomeric state of 68Br was estimated. The results suggest that secondary fragmentation reactions, where relatively few nucleons are removed from the projectile, offer an alternative way to search for new isotopes, as these reactions populate preferentially low-lying states. Keywords: Radioactive beams, New isotope, Direct reaction

Published
2019
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11. Three-body breakup of 6He and its halo structure

Author

Y.L. Sun, T. Nakamura, Y. Kondo, Y. Satou, J. Lee, T. Matsumoto, K. Ogata, Y. Kikuchi, N. Aoi, Y. Ichikawa, K. Ieki, M. Ishihara, T. Kobayshi, T. Motobayashi, H. Otsu, H. Sakurai, T. Shimamura, S. Shimoura, T. Shinohara, T. Sugimoto, S. Takeuchi, Y. Togano, and K. Yoneda

Subjects
Coulomb breakup, Nuclear breakup, Electric dipole response, Halo nuclei, 208Pb(6He, α+2n)X, 12C(6He, α+2n)X, Physics, QC1-999
Abstract

The Borromean halo nucleus 6He has been studied by a kinematically complete measurement of Coulomb and nuclear breakup into α + 2n on Pb and C targets at 70 MeV/nucleon. Fully quantum-mechanical four-body breakup calculations reproduce the energy and angular differential cross sections below Erel∼1 MeV for both targets. The model used here reproduces the 6He ground-state properties as well as α-n and n-n scattering data and predicts an average opening angle 〈θnn〉 of 68∘ between the two halo neutrons. However, the model underestimates the breakup cross sections for higher Erel, indicating a possible contribution from the inelastic breakup. Alternatively, we examine the empirically modified calculations that reproduce the energy-differential cross sections for a wide range of scattering angles for both targets. The extracted B(E1) peaks at Erel∼1.4 MeV and amounts to 1.6(2) e2fm2 for Erel ≤ 20 MeV, resulting 〈θnn〉 = 56−10+9 degrees. In either interpretation, the current results show evidence of the dineutron spatial correlation in 6He.

Published
2021
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12. First spectroscopic study of 51Ar by the (p,2p) reaction

Author

M.M. Juhász, Z. Elekes, D. Sohler, Y. Utsuno, K. Yoshida, T. Otsuka, K. Ogata, P. Doornenbal, A. Obertelli, H. Baba, F. Browne, D. Calvet, F. Château, S. Chen, N. Chiga, A. Corsi, M.L. Cortés, A. Delbart, J.-M. Gheller, A. Giganon, A. Gillibert, C. Hilaire, T. Isobe, T. Kobayashi, Y. Kubota, V. Lapoux, T. Motobayashi, I. Murray, H. Otsu, V. Panin, N. Paul, W. Rodriguez, H. Sakurai, M. Sasano, D. Steppenbeck, L. Stuhl, Y.L. Sun, Y. Togano, T. Uesaka, K. Wimmer, K. Yoneda, N.L. Achouri, O. Aktas, T. Aumann, L.X. Chung, Zs. Dombrádi, F. Flavigny, S. Franchoo, I. Gašparić, R.-B. Gerst, J. Gibelin, K.I. Hahn, D. Kim, T. Koiwai, Y. Kondo, P. Koseoglou, J. Lee, C. Lehr, B.D. Linh, H.N. Liu, T. Lokotko, M. MacCormick, K. Moschner, T. Nakamura, S.Y. Park, D. Rossi, E. Sahin, P.-A. Söderström, S. Takeuchi, H. Törnqvist, V. Vaquero, V. Wagner, S. Wang, V. Werner, X. Xu, H. Yamada, D. Yan, Z. Yang, M. Yasuda, and L. Zanetti

Subjects
Proton knock-out reaction, γ-ray spectroscopy, Invariant mass method, Nuclear structure, Shell closure, Physics, QC1-999
Abstract

The nuclear structure of 51Ar, an uncharted territory so far, was studied by the (p,2p) reaction using γ-ray spectroscopy for the bound states and the invariant mass method for the unbound states. Two peaks were detected in the γ-ray spectrum and six peaks were observed in the 50Ar+n relative energy spectrum. Comparing the results to our shell-model calculations, two bound and six unbound states were established. Three of the unbound states could only be placed tentatively due to the low number of counts in the relative energy spectrum of events associated with the decay through the first excited state of 50Ar. The low cross sections populating the two bound states of 51Ar could be interpreted as a clear signature for the presence of significant subshell closures at neutron numbers 32 and 34 in argon isotopes. It was also revealed that due to the two valence holes, unbound collective states coexist with individual-particle states in 51Ar.

Published
2021
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13. Restoration of the natural E(1/21+) - E(3/21+) energy splitting in odd-K isotopes towards N = 40

Author

Y.L. Sun, A. Obertelli, P. Doornenbal, C. Barbieri, Y. Chazono, T. Duguet, H.N. Liu, P. Navrátil, F. Nowacki, K. Ogata, T. Otsuka, F. Raimondi, V. Somà, Y. Utsuno, K. Yoshida, N. Achouri, H. Baba, F. Browne, D. Calvet, F. Château, S. Chen, N. Chiga, A. Corsi, M.L. Cortés, A. Delbart, J.-M. Gheller, A. Giganon, A. Gillibert, C. Hilaire, T. Isobe, T. Kobayashi, Y. Kubota, V. Lapoux, T. Motobayashi, I. Murray, H. Otsu, V. Panin, N. Paul, W. Rodriguez, H. Sakurai, M. Sasano, D. Steppenbeck, L. Stuhl, Y. Togano, T. Uesaka, K. Wimmer, K. Yoneda, O. Aktas, T. Aumann, L.X. Chung, F. Flavigny, S. Franchoo, I. Gašparić, R.-B. Gerst, J. Gibelin, K.I. Hahn, D. Kim, T. Koiwai, Y. Kondo, P. Koseoglou, J. Lee, C. Lehr, B.D. Linh, T. Lokotko, M. MacCormick, K. Moschner, T. Nakamura, S.Y. Park, D. Rossi, E. Sahin, D. Sohler, P.-A. Söderström, S. Takeuchi, H. Törnqvist, V. Vaquero, V. Wagner, S. Wang, V. Werner, X. Xu, H. Yamada, D. Yan, Z. Yang, M. Yasuda, and L. Zanetti

Subjects
Physics, QC1-999
Abstract

We report on the first γ-ray spectroscopy of 51,53K produced via the 52,54Ca(p,2p) reactions at ∼250 MeV/nucleon. Unambiguous final-state angular-momentum assignments were achieved for beam intensities down to few particles per second by using a new technique based on reaction vertex tracking combined with a thick liquid-hydrogen target. Through γ-ray spectroscopy and exclusive parallel momentum distribution analysis, 3/2+ ground states and 1/2+ first excited states in 51,53K were established quantifying the natural ordering of the 1d3/2 and 2s1/2 proton-hole states that are restored at N = 32 and 34. State-of-the-art ab initio calculations and shell-model calculations with improved phenomenological effective interactions reproduce the present data and predict consistently the increase of the E(1/21+) - E(3/21+) energy differences towards N = 40. Keywords: Spectroscopy, Shell evolution, 51K, 53K

Published
2020
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14. Shell evolution of N = 40 isotones towards 60Ca: First spectroscopy of 62Ti

Author

M.L. Cortés, W. Rodriguez, P. Doornenbal, A. Obertelli, J.D. Holt, S.M. Lenzi, J. Menéndez, F. Nowacki, K. Ogata, A. Poves, T.R. Rodríguez, A. Schwenk, J. Simonis, S.R. Stroberg, K. Yoshida, L. Achouri, H. Baba, F. Browne, D. Calvet, F. Château, S. Chen, N. Chiga, A. Corsi, A. Delbart, J.-M. Gheller, A. Giganon, A. Gillibert, C. Hilaire, T. Isobe, T. Kobayashi, Y. Kubota, V. Lapoux, H.N. Liu, T. Motobayashi, I. Murray, H. Otsu, V. Panin, N. Paul, H. Sakurai, M. Sasano, D. Steppenbeck, L. Stuhl, Y.L. Sun, Y. Togano, T. Uesaka, K. Wimmer, K. Yoneda, O. Aktas, T. Aumann, L.X. Chung, F. Flavigny, S. Franchoo, I. Gašparić, R.-B. Gerst, J. Gibelin, K.I. Hahn, D. Kim, T. Koiwai, Y. Kondo, P. Koseoglou, J. Lee, C. Lehr, B.D. Linh, T. Lokotko, M. MacCormick, K. Moschner, T. Nakamura, S.Y. Park, D. Rossi, E. Sahin, D. Sohler, P.-A. Söderström, S. Takeuchi, H. Toernqvist, V. Vaquero, V. Wagner, S. Wang, V. Werner, X. Xu, H. Yamada, D. Yan, Z. Yang, M. Yasuda, and L. Zanetti

Subjects
Physics, QC1-999
Abstract

Excited states in the N=40 isotone 62Ti were populated via the 63V(p,2p)62Ti reaction at ∼200 MeV/nucleon at the Radioactive Isotope Beam Factory and studied using γ-ray spectroscopy. The energies of the 21+→0gs+ and 41+→21+ transitions, observed here for the first time, indicate a deformed 62Ti ground state. These energies are increased compared to the neighboring 64Cr and 66Fe 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. The shell-model calculations for 62Ti show a dominant configuration with four neutrons excited across the N=40 gap. Likewise, they indicate that the N=40 island of inversion extends down to Z=20, disfavoring a possible doubly magic character of the elusive 60Ca. Keywords: Shell evolution, Radioactive beams, Gamma-ray spectroscopy

Published
2020
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15. Shape coexistence and isospin symmetry in A = 70 nuclei: Spectroscopy of the Tz = −1 nucleus 70Kr

Author

K. Wimmer, W. Korten, T. Arici, P. Doornenbal, P. Aguilera, A. Algora, T. Ando, H. Baba, B. Blank, A. Boso, S. Chen, A. Corsi, P. Davies, G. de Angelis, G. de France, D.T. Doherty, J. Gerl, R. Gernhäuser, D. Jenkins, S. Koyama, T. Motobayashi, S. Nagamine, M. Niikura, A. Obertelli, D. Lubos, B. Rubio, E. Sahin, T.Y. Saito, H. Sakurai, L. Sinclair, D. Steppenbeck, R. Taniuchi, R. Wadsworth, and M. Zielinska

Subjects
Physics, QC1-999
Abstract

Excited states in the Tz=−1 nucleus 70Kr have been populated using inelastic scattering of a radioactive 70Kr beam as well as one- and two-neutron removal reactions from 71,72Kr at intermediate beam energies. The level scheme of 70Kr was constructed from the observed γ-ray transitions and coincidences. Tentative spin and parity assignments were made based on comparison with the mirror nucleus 70Se. A second 2+ state and a candidate for the corresponding 42+ state suggest shape coexistence in 70Kr. Keywords: Radioactive beams, Gamma-ray spectroscopy, Mirror symmetry, Shape coexistence

Published
2018
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16. Spectroscopy of 2565,67Mn: Strong coupling in the N = 40 'island of inversion'

Author

X.Y. Liu, Z. Liu, B. Ding, P. Doornenbal, A. Obertelli, S.M. Lenzi, P.M. Walker, L.X. Chung, B.D. Linh, G. Authelet, H. Baba, D. Calvet, F. Château, A. Corsi, A. Delbart, J.-M. Gheller, A. Gillibert, T. Isobe, V. Lapoux, M. Matsushita, S. Momiyama, T. Motobayashi, M. Niikura, F. Nowacki, H. Otsu, C. Péron, A. Peyaud, E.C. Pollacco, J.-Y. Roussé, H. Sakurai, M. Sasano, Y. Shiga, S. Takeuchi, R. Taniuchi, T. Uesaka, H. Wang, K. Yoneda, Y.H. Lam, T.H. Huang, M.D. Sun, W.Q. Zhang, H.Y. Lu, D.S. Hou, F. Browne, Zs. Dombradi, S. Franchoo, F. Giacoppo, A. Gottardo, K. Hadynska-Klek, Z. Korkulu, S. Koyama, Y. Kubota, J. Lee, M. Lettmann, R. Lozeva, K. Matsui, T. Miyazaki, S. Nishimura, C. Louchart, L. Olivier, S. Ota, Z. Patel, E. Sahin, C. Santamaria, C. Shand, P.-A. Söderström, G.L. Stefan, D. Steppenbeck, T. Sumikama, D. Suzuki, Zs. Vajta, V. Werner, J. Wu, Z. Xu, X.H. Zhou, Y.H. Zhang, H.S. Xu, and F.S. Zhang

Subjects
Physics, QC1-999
Abstract

Excited states in 63,65,67Mn were studied via in-beam γ-ray spectroscopy following knockout reactions from 68Fe. Similar level schemes, consisting of the 11/2−, 9/2−, 7/2− and 5/2g.s.− level sequence, connected by I→I−1 transitions, were established, the first time for 65,67Mn. Their level structures show features consistent with strongly-coupled rotational bands with K=5/2. State-of-the-art shell-model calculations with the modified LNPS effective interaction reproduce the observed levels remarkably well and suggest the dominance of 4-particle-4-hole neutron configurations for all the states. The data on the low-lying excited states of odd-mass 53−67Mn provide a textbook example of nuclear structure evolution from weak coupling through decoupling to strong coupling along a single isotopic chain on the n-rich side of the β stability line. These results help to deepen our understanding of the N=40 “island of inversion”. Keywords: In-beam γ-ray spectroscopy, “Island of inversion” around N=40, Strong coupling, Structure evolution

Published
2018
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17. Proton single particle energies next to 78Ni: Spectroscopy of 77Cu via single proton knock-out reaction

Author

Zs. Vajta, D. Sohler, Y. Shiga, K. Yoneda, K. Sieja, D. Steppenbeck, Zs. Dombrádi, N. Aoi, P. Doornenbal, J. Lee, H. Liu, M. Matsushita, S. Takeuchi, H. Wang, H. Baba, P. Bednarczyk, Zs. Fülöp, S. Go, T. Hashimoto, E. Ideguchi, K. Ieki, K. Kobayashi, Y. Kondo, R. Minakata, T. Motobayashi, D. Nishimura, H. Otsu, H. Sakurai, Y. Sun, A. Tamaii, R. Tanaka, Z. Tian, T. Yamamoto, X. Yang, Z. Yang, Y. Ye, R. Yokoyama, and J. Zenihiro

Subjects
Physics, QC1-999
Abstract

Excited states of 77Cu have been investigated by use of single proton knock-out reaction at the Radioactive Isotope Beam Factory in RIKEN in order to reveal the main components of the proton single-particle states. Three excited states were observed at 271, 902 and 2068 keV in 77Cu. The lowest-energy excited state follows the trend predicted for the crossing of the 3/21− and 5/21− states. Comparing the excitation energies of the 3/2−, 5/2− and 7/2− levels from 69Cu to 77Cu one can see that the Z=28 shell gap between the p3/2 and f7/2 states is rather stable, while the f5/2−f7/2 spin–orbit splitting decreases by ∼1.5 MeV in agreement with shell model calculations using the tensor force.

Published
2018
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18. Shell evolution beyond Z=28 and N=50: Spectroscopy of 81,82,83,84Zn

Author

C.M. Shand, Zs. Podolyák, M. Górska, P. Doornenbal, A. Obertelli, F. Nowacki, T. Otsuka, K. Sieja, J.A. Tostevin, Y. Tsunoda, G. Authelet, H. Baba, D. Calvet, A. Château, S. Chen, A. Corsi, A. Delbart, J.M. Gheller, A. Giganon, A. Gillibert, T. Isobe, V. Lapoux, M. Matsushita, S. Momiyama, T. Motobayashi, M. Niikura, H. Otsu, N. Paul, C. Péron, A. Peyaud, E.C. Pollacco, J.-Y. Roussé, H. Sakurai, C. Santamaria, M. Sasano, Y. Shiga, D. Steppenbeck, S. Takeuchi, R. Taniuchi, T. Uesaka, H. Wang, K. Yoneda, T. Ando, T. Arici, A. Blazhev, F. Browne, A.M. Bruce, R.J. Carroll, L.X. Chung, M.L. Cortés, M. Dewald, B. Ding, Zs. Dombrádi, F. Flavigny, S. Franchoo, F. Giacoppo, A. Gottardo, K. Hadyńska-Klęk, A. Jungclaus, Z. Korkulu, S. Koyama, Y. Kubota, J. Lee, M. Lettmann, B.D. Linh, J. Liu, Z. Liu, C. Lizarazo, C. Louchart, R. Lozeva, K. Matsui, T. Miyazaki, K. Moschner, M. Nagamine, N. Nakatsuka, S. Nishimura, C.R. Nita, C.R. Nobs, L. Olivier, S. Ota, R. Orlandi, Z. Patel, P.H. Regan, M. Rudigier, E. Şahin, T. Saito, P.-A. Söderström, I. Stefan, T. Sumikama, D. Suzuki, Zs. Vajta, V. Vaquero, V. Werner, K. Wimmer, J. Wu, and Z.Y. Xu

Subjects
Physics, QC1-999
Abstract

We report on the measurement of new low-lying states in the neutron-rich 81,82,83,84Zn nuclei via in-beam γ-ray spectroscopy. These include the 41+→21+ transition in 82Zn, the 21+→0g.s.+ and 41+→21+ transitions in 84Zn, and low-lying states in 81,83Zn were observed for the first time. The reduced E(21+) energies and increased E(41+)/E(2+1) ratios at N=52, 54 compared to those in 80Zn attest that the magicity is confined to the neutron number N=50 only. The deduced level schemes are compared to three state-of-the-art shell model calculations and a good agreement is observed with all three calculations. The newly observed 2+ and 4+ levels in 84Zn suggest the onset of deformation towards heavier Zn isotopes, which has been incorporated by taking into account the upper sdg orbitals in the Ni78-II and the PFSDG-U models.

Published
2017
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19. Single-neutron knockout from 20C and the structure of 19C

Author

J.W. Hwang, S. Kim, Y. Satou, N.A. Orr, Y. Kondo, T. Nakamura, J. Gibelin, N.L. Achouri, T. Aumann, H. Baba, F. Delaunay, P. Doornenbal, N. Fukuda, N. Inabe, T. Isobe, D. Kameda, D. Kanno, N. Kobayashi, T. Kobayashi, T. Kubo, S. Leblond, J. Lee, F.M. Marqués, R. Minakata, T. Motobayashi, D. Murai, T. Murakami, K. Muto, T. Nakashima, N. Nakatsuka, A. Navin, S. Nishi, S. Ogoshi, H. Otsu, H. Sato, Y. Shimizu, H. Suzuki, K. Takahashi, H. Takeda, S. Takeuchi, R. Tanaka, Y. Togano, A.G. Tuff, M. Vandebrouck, and K. Yoneda

Subjects
Heavy-ion knockout, Invariant mass spectroscopy, Shell evolution, Physics, QC1-999
Abstract

The low-lying unbound level structure of the halo nucleus 19C has been investigated using single-neutron knockout from 20C on a carbon target at 280 MeV/nucleon. The invariant mass spectrum, derived from the momenta of the forward going beam velocity 18C fragment and neutrons, was found to be dominated by a very narrow near threshold (Erel=0.036(1) MeV) peak. Two less strongly populated resonance-like features were also observed at Erel=0.84(4) and 2.31(3) MeV, both of which exhibit characteristics consistent with neutron p-shell hole states. Comparisons of the energies, measured cross sections and parallel momentum distributions to the results of shell-model and eikonal reaction calculations lead to spin-parity assignments of 5/21+ and 1/21− for the levels at Ex=0.62(9) and 2.89(10) MeV with Sn=0.58(9) MeV. Spectroscopic factors were also deduced and found to be in reasonable accord with shell-model calculations. The valence neutron configuration of the 20C ground state is thus seen to include, in addition to the known 1s1/22 component, a significant 0d5/22 contribution. The level scheme of 19C, including significantly the 1/21− cross-shell state, is well accounted for by the YSOX shell-model interaction developed from the monopole-based universal interaction.

Published
2017
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20. Observation of isoscalar and isovector dipole excitations in neutron-rich 20O

Author

N. Nakatsuka, H. Baba, T. Aumann, R. Avigo, S.R. Banerjee, A. Bracco, C. Caesar, F. Camera, S. Ceruti, S. Chen, V. Derya, P. Doornenbal, A. Giaz, A. Horvat, K. Ieki, T. Inakura, N. Imai, T. Kawabata, N. Kobayashi, Y. Kondo, S. Koyama, M. Kurata-Nishimura, S. Masuoka, M. Matsushita, S. Michimasa, B. Million, T. Motobayashi, T. Murakami, T. Nakamura, T. Ohnishi, H.J. Ong, S. Ota, H. Otsu, T. Ozaki, A. Saito, H. Sakurai, H. Scheit, F. Schindler, P. Schrock, Y. Shiga, M. Shikata, S. Shimoura, D. Steppenbeck, T. Sumikama, I. Syndikus, H. Takeda, S. Takeuchi, A. Tamii, R. Taniuchi, Y. Togano, J. Tscheuschner, J. Tsubota, H. Wang, O. Wieland, K. Wimmer, Y. Yamaguchi, K. Yoneda, and J. Zenihiro

Subjects
O20, Low-energy dipole excitation, Inelastic α scattering, Virtual-photon excitation, Physics, QC1-999
Abstract

The isospin characters of low-energy dipole excitations in neutron-rich unstable nucleus 20O were investigated, for the first time in unstable nuclei. Two spectra obtained from a dominant isovector probe (O20+Au) and a dominant isoscalar probe (O20+α) were compared and analyzed by the distorted-wave Born approximation to extract independently the isovector and isoscalar dipole strengths. Two known 1− states with large isovector dipole strengths at energies of 5.36(5) MeV (11−) and 6.84(7) MeV (12−) were also excited by the isoscalar probe. These two states were found to have different isoscalar dipole strengths, 2.70(32)% (11−) and 0.67(12)% (12−), respectively, in exhaustion of the isoscalar dipole-energy-weighted sum rule. The difference in isoscalar strength indicated that they have different underlying structures.

Published
2017
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21. Intruder configurations in the ground state of 30Ne

Author

H.N. Liu, J. Lee, P. Doornenbal, H. Scheit, S. Takeuchi, N. Aoi, K.A. Li, M. Matsushita, D. Steppenbeck, H. Wang, H. Baba, E. Ideguchi, N. Kobayashi, Y. Kondo, G. Lee, S. Michimasa, T. Motobayashi, A. Poves, H. Sakurai, M. Takechi, Y. Togano, J.A. Tostevin, and Y. Utsuno

Subjects
Intruder configurations, One-neutron knockout reactions 12C(30Ne, 29Ne+γ)X, Physics, QC1-999
Abstract

We report on the first detailed study of intruder configurations in the ground state of 30Ne by means of the 12C(30Ne, 29Ne+γ)X one-neutron knockout reaction at 228 MeV/nucleon. Using a combined analysis of individual parallel momentum distributions and partial cross sections we find: (a) comparable p- and d-wave removal strength to 29Ne final states with excitation energies below 200 keV, and (b) significant p-wave removal strength to the 620 keV state of 29Ne, and (c) no evidence for f-wave intruder strength leading to bound 29Ne final states. The SDPF-U-MIX shell model calculation in the sd–pf model space provides a better overall agreement with the measured energy levels of 29Ne and the fp-intruder amplitudes in 30Ne than the SDPF-M prediction, suggesting that the refinement of the sd–pf cross shell interaction and extension of the model space to include the 2p1/2 and 1f5/2 levels are important for understanding the island of inversion.

Published
2017
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22. Structure of 13Be probed via quasi-free scattering

Author

A. Corsi, Y. Kubota, J. Casal, M. Gómez-Ramos, A.M. Moro, G. Authelet, H. Baba, C. Caesar, D. Calvet, A. Delbart, M. Dozono, J. Feng, F. Flavigny, J.-M. Gheller, J. Gibelin, A. Giganon, A. Gillibert, K. Hasegawa, T. Isobe, Y. Kanaya, S. Kawakami, D. Kim, Y. Kiyokawa, M. Kobayashi, N. Kobayashi, T. Kobayashi, Y. Kondo, Z. Korkulu, S. Koyama, V. Lapoux, Y. Maeda, F.M. Marqués, T. Motobayashi, T. Miyazaki, T. Nakamura, N. Nakatsuka, Y. Nishio, A. Obertelli, A. Ohkura, N.A. Orr, S. Ota, H. Otsu, T. Ozaki, V. Panin, S. Paschalis, E.C. Pollacco, S. Reichert, J.-Y. Rousse, A.T. Saito, S. Sakaguchi, M. Sako, C. Santamaria, M. Sasano, H. Sato, M. Shikata, Y. Shimizu, Y. Shindo, L. Stuhl, T. Sumikama, Y.L. Sun, M. Tabata, Y. Togano, J. Tsubota, T. Uesaka, Z.H. Yang, J. Yasuda, K. Yoneda, and J. Zenihiro

Subjects
Physics, QC1-999
Abstract

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. Keywords: Quasi-free scattering, Borromean nuclei, Three-body model, Resonances

Published
2019
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23. Multiple Mechanisms in Proton-Induced Nucleon Removal at ∼100 MeV/Nucleon

Author

T. Pohl, Y. L. Sun, A. Obertelli, J. Lee, M. Gómez-Ramos, K. Ogata, K. Yoshida, B. S. Cai, C. X. Yuan, B. A. Brown, H. Baba, D. Beaumel, A. Corsi, J. Gao, J. Gibelin, A. Gillibert, K. I. Hahn, T. Isobe, D. Kim, Y. Kondo, T. Kobayashi, Y. Kubota, P. Li, P. Liang, H. N. Liu, J. Liu, T. Lokotko, F. M. Marqués, Y. Matsuda, T. Motobayashi, T. Nakamura, N. A. Orr, H. Otsu, V. Panin, S. Y. Park, S. Sakaguchi, M. Sasano, H. Sato, H. Sakurai, Y. Shimizu, A. I. Stefanescu, L. Stuhl, D. Suzuki, Y. Togano, D. Tudor, T. Uesaka, H. Wang, X. Xu, Z. H. Yang, K. Yoneda, and J. Zenihiro

Subjects
General Physics and Astronomy
Published
2023

24. Interaction cross section study of the two-neutron halo nucleus 22C

Author

Y. Togano, T. Nakamura, Y. Kondo, J.A. Tostevin, A.T. Saito, J. Gibelin, N.A. Orr, N.L. Achouri, T. Aumann, H. Baba, F. Delaunay, P. Doornenbal, N. Fukuda, J.W. Hwang, N. Inabe, T. Isobe, D. Kameda, D. Kanno, S. Kim, N. Kobayashi, T. Kobayashi, T. Kubo, S. Leblond, J. Lee, F.M. Marqués, R. Minakata, T. Motobayashi, D. Murai, T. Murakami, K. Muto, T. Nakashima, N. Nakatsuka, A. Navin, S. Nishi, S. Ogoshi, H. Otsu, H. Sato, Y. Satou, Y. Shimizu, H. Suzuki, K. Takahashi, H. Takeda, S. Takeuchi, R. Tanaka, A.G. Tuff, M. Vandebrouck, and K. Yoneda

Subjects
Interaction cross section, Matter radius, Two-neutron halo nucleus 22C, Physics, QC1-999
Abstract

The interaction cross sections (σI) of the very neutron-rich carbon isotopes 19C, 20C and 22C have been measured on a carbon target at 307, 280, and 235 MeV/nucleon, respectively. A σI of 1.280±0.023 b was obtained for 22C, significantly larger than for 19,20C, supporting the halo character of 22C. A 22C root-mean-squared matter radius of 3.44±0.08 fm was deduced using a four-body Glauber reaction model. This value is smaller than an earlier estimate (of 5.4±0.9 fm) derived from a σI measurement on a hydrogen target at 40 MeV/nucleon. These new, higher-precision σI data provide stronger constraints for assessing the consistency of theories describing weakly bound nuclei.

Published
2016
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25. Extended p3/2 Neutron Orbital and the N=32 Shell Closure in Ca52

Author

M. Enciu, H. N. Liu, A. Obertelli, P. Doornenbal, F. Nowacki, K. Ogata, A. Poves, K. Yoshida, N. L. Achouri, H. Baba, F. Browne, D. Calvet, F. Château, S. Chen, N. Chiga, A. Corsi, M. L. Cortés, A. Delbart, J-M. Gheller, A. Giganon, A. Gillibert, C. Hilaire, T. Isobe, T. Kobayashi, Y. Kubota, V. Lapoux, T. Motobayashi, I. Murray, H. Otsu, V. Panin, N. Paul, W. Rodriguez, H. Sakurai, M. Sasano, D. Steppenbeck, L. Stuhl, Y. L. Sun, Y. Togano, T. Uesaka, K. Wimmer, K. Yoneda, O. Aktas, T. Aumann, L. X. Chung, F. Flavigny, S. Franchoo, I. Gasparic, R.-B. Gerst, J. Gibelin, K. I. Hahn, D. Kim, Y. Kondo, P. Koseoglou, J. Lee, C. Lehr, P. J. Li, B. D. Linh, T. Lokotko, M. MacCormick, K. Moschner, T. Nakamura, S. Y. Park, D. Rossi, E. Sahin, P.-A. Söderström, D. Sohler, S. Takeuchi, H. Toernqvist, V. Vaquero, V. Wagner, S. Wang, V. Werner, X. Xu, H. Yamada, D. Yan, Z. Yang, M. Yasuda, and L. Zanetti

Subjects
General Physics and Astronomy
Published
2022

26. Different mechanism of two-proton emission from proton-rich nuclei 23Al and 22Mg

Author

Y.G. Ma, D.Q. Fang, X.Y. Sun, P. Zhou, Y. Togano, N. Aoi, H. Baba, X.Z. Cai, X.G. Cao, J.G. Chen, Y. Fu, W. Guo, Y. Hara, T. Honda, Z.G. Hu, K. Ieki, Y. Ishibashi, Y. Ito, N. Iwasa, S. Kanno, T. Kawabata, H. Kimura, Y. Kondo, K. Kurita, M. Kurokawa, T. Moriguchi, H. Murakami, H. Ooishi, K. Okada, S. Ota, A. Ozawa, H. Sakurai, S. Shimoura, R. Shioda, E. Takeshita, S. Takeuchi, W.D. Tian, H.W. Wang, J.S. Wang, M. Wang, K. Yamada, Y. Yamada, Y. Yasuda, K. Yoneda, G.Q. Zhang, and T. Motobayashi

Subjects
Physics, QC1-999
Abstract

Two-proton relative momentum (qpp) and opening angle (θpp) distributions from the three-body decay of two excited proton-rich nuclei, namely Al23→p+p+Na21 and Mg22→p+p+Ne20, have been measured with the projectile fragment separator (RIPS) at the RIKEN RI Beam Factory. An evident peak at qpp∼20 MeV/c as well as a peak in θpp around 30° are seen in the two-proton break-up channel from a highly-excited 22Mg. In contrast, such peaks are absent for the 23Al case. It is concluded that the two-proton emission mechanism of excited 22Mg is quite different from the 23Al case, with the former having a favorable diproton emission component at a highly excited state and the latter dominated by the sequential decay process.

Published
2015
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27. Neutron-driven collectivity in light tin isotopes: Proton inelastic scattering from 104Sn

Author

A. Corsi, S. Boissinot, A. Obertelli, P. Doornenbal, M. Dupuis, F. Lechaftois, M. Matsushita, S. Péru, S. Takeuchi, H. Wang, N. Aoi, H. Baba, P. Bednarczyk, M. Ciemala, A. Gillibert, T. Isobe, A. Jungclaus, V. Lapoux, J. Lee, M. Martini, K. Matsui, T. Motobayashi, D. Nishimura, S. Ota, E. Pollacco, H. Sakurai, C. Santamaria, Y. Shiga, D. Sohler, D. Steppenbeck, and R. Taniuchi

Subjects
Physics, QC1-999
Abstract

Inelastic scattering cross sections to individual bound excited states of 104Sn were measured at 150 MeV/u beam energy and analyzed to evaluate the contribution of neutron and proton collectivity. State-of-the-art Quasi-Particle Random Phase Approximation (QRPA) with the D1M Gogny interaction reproduces the experimental proton collectivity and our inelastic scattering cross sections once used as input for a reaction calculation together with the Jeukenne–Lejeune–Mahaux (JLM) potentials. Experimental inelastic scattering cross section decreases by 40(24)% from 112Sn to 104Sn. The present work shows that (i) proton and neutron collectivities are proportional over a large range of tin isotopes (including 104Sn), as is typical for isoscalar excitations, and (ii) the neutron collectivity dominates. It suggests that the plateau in the mass range A=106–112 displayed by E2 transition probabilities is driven by neutron collectivity. Keywords: Collectivity, Inelastic scattering, Gamma spectroscopy

Published
2015
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28. Neutron occupancy of the 0d5/2 orbital and the N=16 shell closure in 24O

Author

K. Tshoo, Y. Satou, C.A. Bertulani, H. Bhang, S. Choi, T. Nakamura, Y. Kondo, S. Deguchi, Y. Kawada, Y. Nakayama, K.N. Tanaka, N. Tanaka, Y. Togano, N. Kobayashi, N. Aoi, M. Ishihara, T. Motobayashi, H. Otsu, H. Sakurai, S. Takeuchi, K. Yoneda, F. Delaunay, J. Gibelin, F.M. Marqués, N.A. Orr, T. Honda, T. Kobayashi, T. Sumikama, Y. Miyashita, K. Yoshinaga, M. Matsushita, S. Shimoura, D. Sohler, J.W. Hwang, T. Zheng, Z.H. Li, and Z.X. Cao

Subjects
Physics, QC1-999
Abstract

One-neutron knockout from 24O leading to the first excited state in 23O has been measured for a proton target at a beam energy of 62 MeV/nucleon. The decay energy spectrum of the neutron unbound state of 23O was reconstructed from the measured four momenta of the 22O fragment and emitted neutron. A sharp peak was found at Edecay=50±3 keV, corresponding to an excited state in 23O at 2.78±0.11 MeV, as observed in previous measurements. The longitudinal momentum distribution for this state was consistent with d-wave neutron knockout, providing support for a Jπ assignment of 5/2+. The associated spectroscopic factor was deduced to be C2S(0d5/2)=4.1±0.4 by comparing the measured cross section (σ−1nexp=61±6 mb) with a distorted wave impulse approximation calculation. Such a large occupancy for the neutron 0d5/2 orbital is in line with the N=16 shell closure in 24O.

Published
2014
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29. Study of spin-isospin responses of radioactive nuclei with the background-reduced neutron spectrometer, PANDORA

Author

N. Fukuda, Takashi Nakamura, H. Sakai, Yohei Shimizu, J. Gibelin, Makoto Yasuda, Tomotsugu Wakasa, M. Nishimura, J. Gao, Masashige Matsumoto, S. Franchoo, H. Miki, H. Kasahara, T. Harada, Masaki Sasano, D. Tudor, Toshio Kobayashi, T. Isobe, G. G. Kiss, Tomohiro Uesaka, Yasuhiro Togano, Susumu Shimoura, Atsumi Saito, N. Zhang, I. C. Stefanescu, E. Takada, Zoltán Halász, L. Trache, Yuya Kubota, D. Kim, T. Shimada, Shoko Koyama, Y. Fujino, Juzo Zenihiro, Z. Korkulu, D. Inomoto, Zaihong Yang, H. Sato, H. N. Liu, A. Spiridon, M. Miwa, H. Suzuki, L. Stuhl, V. Panin, H. Baba, Yosuke Kondo, S. Park, K. Yoneda, T. Motobayashi, Y. L. Sun, T. Tomai, I. S. Hahn, Kentaro Yako, X. Sun, A. Kurihara, M.N. Harakeh, Y. Hirai, D. S. Ahn, A. I. Chilug, Hideaki Otsu, Hiroki Yamada, Shin'ichiro Michimasa, K. Yoshida, Institut de Physique Nucléaire d'Orsay (IPNO), Université Paris-Sud - Paris 11 (UP11)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de physique corpusculaire de Caen (LPCC), Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Normandie Université (NU)-École Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN), Normandie Université (NU)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), Département de Physique Nucléaire (ex SPhN) (DPHN), Institut de Recherches sur les lois Fondamentales de l'Univers (IRFU), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay, Research unit Nuclear & Hadron Physics, Centre National de la Recherche Scientifique (CNRS)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Paris-Sud - Paris 11 (UP11), and Normandie Université (NU)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)

Subjects
Nuclear and High Energy Physics, Nuclear Theory, n) reactions, Inverse-kinematics (p, n) reactions, 01 natural sciences, Low-energy neutron detector, Inverse-kinematics [formula omitted] reactions, Nuclear physics, 0103 physical sciences, Figure-of-Merit (FoM), Neutron detection, Neutron, 010306 general physics, Spin (physics), Nuclear Experiment, Instrumentation, Gamow-Teller transition, DETECTOR, Real-time pulse-shape discrimination, Physics, [PHYS]Physics [physics], Spin-isospin response, Spectrometer, 010308 nuclear & particles physics, Figure-of-Merit (RIM), Detector, PULSE-SHAPE DISCRIMINATION, PLASTIC SCINTILLATOR, Inverse-kinematics (p, Isospin, Ground state, Beam (structure)
Abstract

The status of a project to measure spin-isospin responses of neutron drip-line nuclei using a new low-energy neutron detector, PANDORA (Particle Analyzer Neutron Detector Of Real-time Acquisition), is reported. The performance of PANDORA was characterized by the 6He(p,n)6Li reaction in inverse kinematics at the HIMAC facility in Chiba. Observation of the strong transition to the ground state in 6Li is discussed. Preliminary results of 11Li(p,n)11Be and 14Be(p,n)14B experiments in inverse kinematics at RI Beam Factory (RIBF) of RIKEN Nishina Center are also presented including the exotic decay channel of 11Be→9Li + d. Details of the experimental setup based on PANDORA and the SAMURAI large-acceptance magnetic spectrometer, as well as the combined data-acquisition system are described. The neutron-gamma discrimination capability of PANDORA was evaluated, Figure-of-Merit (FoM) values higher than those found in the literature for similar materials were derived from experimental data.

Published
2020

30. γ -ray spectroscopy of low-lying yrast and non-yrast states in neutron-rich Kr94,95,96

Author

R.-B. Gerst, A. Blazhev, K. Moschner, P. Doornenbal, A. Obertelli, K. Nomura, J.-P. Ebran, S. Hilaire, J. Libert, G. Authelet, H. Baba, D. Calvet, F. Château, S. Chen, A. Corsi, A. Delbart, J.-M. Gheller, A. Giganon, A. Gillibert, V. Lapoux, T. Motobayashi, M. Niikura, N. Paul, J.-Y. Roussé, H. Sakurai, C. Santamaria, D. Steppenbeck, R. Taniuchi, T. Uesaka, T. Ando, T. Arici, F. Browne, A. M. Bruce, R. Caroll, L. X. Chung, M. L. Cortés, M. Dewald, B. Ding, F. Flavigny, S. Franchoo, M. Górska, A. Gottardo, J. Jolie, A. Jungclaus, J. Lee, M. Lettmann, B. D. Linh, J. Liu, Z. Liu, C. Lizarazo, S. Momiyama, S. Nagamine, N. Nakatsuka, C. R. Nita, C. Nobs, L. Olivier, R. Orlandi, Z. Patel, Zs. Podolyák, M. Rudigier, T. Saito, C. Shand, P.-A. Söderström, I. Stefan, V. Vaquero, V. Werner, K. Wimmer, and Z. Xu

Published
2022

31. Silicon tracker array for RIB experiments at SAMURAI

Author

A. I. Stefanescu, V. Panin, L. Trache, T. Motobayashi, H. Otsu, A. Saastamoinen, T. Uesaka, L. Stuhl, J. Tanaka, D. Tudor, I. C. Stefanescu, A. E. Spiridon, K. Yoneda, H. Baba, M. Kurokawa, Y. Togano, Z. Halasz, M. Sasano, S. Ota, Y. Kubota, D. S. Ahn, T. Kobayashi, Z. Elekes, N. Fukuda, H. Takeda, D. Kim, E. Takada, H. Suzuki, K. Yoshida, Y. Shimizu, H. N. Liu, Y. L. Sun, T. Isobe, J. Gibelin, P. J. Li, J. Zenihiro, F. M. Marqués, M. N. Harakeh, G. G. Kiss, A. Kurihara, M. Yasuda, T. Nakamura, S. Park, Z. Yang, T. Harada, M. Nishimura, H. Sato, I. S. Hahn, K. Y. Chae, J. M. Elson, L. G. Sobotka, C. A. Bertulani, Département de Physique Nucléaire (ex SPhN) (DPHN), Institut de Recherches sur les lois Fondamentales de l'Univers (IRFU), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay, Laboratoire de physique corpusculaire de Caen (LPCC), Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Normandie Université (NU)-École Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN), and Normandie Université (NU)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS)

Subjects
Nuclear and High Energy Physics, Physics - Instrumentation and Detectors, FOS: Physical sciences, Instrumentation and Detectors (physics.ins-det), [PHYS.PHYS.PHYS-INS-DET]Physics [physics]/Physics [physics]/Instrumentation and Detectors [physics.ins-det], Nuclear Experiment (nucl-ex), Astrophysics - Instrumentation and Methods for Astrophysics, Instrumentation and Methods for Astrophysics (astro-ph.IM), Nuclear Experiment
Abstract

International audience; This work describes a silicon tracker system developed for experiments with proton-rich radioactive ion beams at the SAMURAI superconducting spectrometer of RIBF at RIKEN. The system is designed for accurate angular reconstruction and atomic number identification of relativistic heavy ions and protons which are simultaneously produced in reactions motivated by studies of proton capture reactions of interest for nuclear astrophysics. The technical characteristics of the tracking array are described in detail as are its performance in two pilot experiments. The physics justification for such a system is also presented.

Published
2022

32. Investigation of the ground-state spin inversion in the neutron-rich Cl47,49 isotopes

Author

Jason D. Holt, Carlo Barbieri, Zaihong Yang, I. Murray, D. M. Rossi, K. I. Hahn, S. Y. Park, C. Hilaire, Kazuyuki Ogata, C. Lehr, H. Baba, Duo Yan, David Steppenbeck, H. Törnqvist, P. Koseoglou, Masahiro Yasuda, V. Lapoux, Yasuhiro Togano, N. L. Achouri, R.-B. Gerst, Alessandra Corsi, T. Lokotko, B. D. Linh, L. Stuhl, H. Wang, Dóra Sohler, M. Gómez-Ramos, Igor Gašparić, H. N. Liu, Y. L. Sun, Takashi Nakamura, E. Sahin, Petr Navrátil, V. Panin, W. Rodriguez, N. Shimizu, J. M. Gheller, A. Moro, Victor Vaquero, L. X. Chung, Thomas Duguet, K. Moschner, Hiroyoshi Sakurai, Kathrin Wimmer, Dong-Wook Kim, A. Delbart, N. T. Khai, V. Wagner, N. Paul, P. Doornenbal, T. Motobayashi, V. Somà, D. Calvet, T. Isobe, K. Yoneda, O. Aktas, V. Werner, Y. Yamada, Thomas Aumann, F. Flavigny, N. D. Ton, T. Kobayashi, A. Giganon, X. X. Xu, F. Château, Hideaki Otsu, Julien Gibelin, Si-Ge Chen, N. T. T. Phuc, P. A. Söderström, A. Gillibert, Nobuyuki Chiga, A. Obertelli, T. Koiwai, Tomohiro Uesaka, F. Browne, M. MacCormick, Satoshi Takeuchi, M. L. Cortés, Masaki Sasano, S. Franchoo, Yutaka Utsuno, Jenny Lee, Yuya Kubota, L. Zanetti, and Yosuke Kondo

Subjects
Physics, Isotope, 010308 nuclear & particles physics, 0103 physical sciences, Neutron, Atomic physics, 010306 general physics, Spin (physics), Ground state, 01 natural sciences, Inversion (discrete mathematics), Nuclear theory
Published
2021

33. Pairing Forces Govern Population of Doubly Magic Ca54 from Direct Reactions

Author

J. M. Gheller, S. Y. Park, K. Yoneda, Masaki Sasano, P. A. Söderström, D. Sohler, D. Körper, H. Simon, A. Gillibert, K. Miki, Satoshi Takeuchi, Yasuhiro Togano, M. MacCormick, R.-B. Gerst, Duo Yan, Tomohiro Uesaka, Fabia Schindler, V. Wagner, B. D. Linh, M. Holl, A. Corsi, N. Paul, Igor Gašparić, H. N. Liu, P. Koseoglou, E. Sahin, Yosuke Kondo, T. Lokotko, T. Isobe, Victor Vaquero, M. L. Cortés, V. Werner, Takashi Nakamura, W. Rodriguez, Zaihong Yang, A. Delbart, S. Franchoo, F. Château, V. Lapoux, P. Doornenbal, K. I. Hahn, L. Stuhl, I. Murray, C. Caesar, Kazuyuki Ogata, C. Lehr, T. Kobayashi, X. X. Xu, C. Hilaire, Si-Ge Chen, Yutaka Utsuno, V. Panin, A. Giganon, Jenny Lee, N. L. Achouri, L. X. Chung, Y. L. Sun, K. Moschner, Yuya Kubota, D. M. Rossi, H. Baba, F. Flavigny, Masahiro Yasuda, L. Zanetti, Kathrin Wimmer, Dong-Wook Kim, O. Aktas, F. Browne, S. Wang, A. Obertelli, J. Kahlbow, Hiroyoshi Sakurai, T. Motobayashi, Julien Gibelin, K. Boretzky, D. Calvet, David Steppenbeck, H. Törnqvist, Thomas Aumann, Nobuyuki Chiga, T. Koiwai, Kazuki Yoshida, Hideaki Otsu, Hirofumi Yamada, and J. Tscheuschner

Subjects
Physics, education.field_of_study, Proton, 010308 nuclear & particles physics, Nuclear Theory, Population, Nuclear shell model, General Physics and Astronomy, 01 natural sciences, 7. Clean energy, Pairing, Excited state, 0103 physical sciences, Neutron, Atomic physics, Nuclear Experiment, 010306 general physics, Nucleon, Ground state, education
Abstract

Direct proton-knockout reactions of ^{55}Sc at ∼220 MeV/nucleon were studied at the RIKEN Radioactive Isotope Beam Factory. Populated states of ^{54}Ca were investigated through γ-ray and invariant-mass spectroscopy. Level energies were calculated from the nuclear shell model employing a phenomenological internucleon interaction. Theoretical cross sections to states were calculated from distorted-wave impulse approximation estimates multiplied by the shell model spectroscopic factors, which describe the wave function overlap of the ^{55}Sc ground state with states in ^{54}Ca. 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 counterintuitive 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.

Published
2021

34. First spectroscopic study of V63 at the N=40 island of inversion

Author

K. Moschner, David Steppenbeck, F. Browne, Jenny Lee, H. Törnqvist, Y. L. Sun, Kathrin Wimmer, Yuya Kubota, A. Gillibert, V. Panin, E. Sahin, L. X. Chung, D. Calvet, T. Isobe, Alessandra Corsi, Dóra Sohler, R.-B. Gerst, M. MacCormick, Yosuke Kondo, F. Château, Hideaki Otsu, P. Doornenbal, Hirofumi Yamada, N. Paul, V. Werner, Satoshi Takeuchi, M. L. Cortés, Masahiro Yasuda, D. M. Rossi, S. Franchoo, C. Lehr, W. Rodriguez, H. Baba, S. Y. Park, Z. Elekes, A. Giganon, Kazuyuki Ogata, Nobuyuki Chiga, Duo Yan, T. Lokotko, L. Zanetti, L. Stuhl, K. Yoneda, T. Koiwai, Takashi Nakamura, A. Delbart, Masaki Sasano, N. L. Achouri, S. Wang, B. D. Linh, Igor Gašparić, H. N. Liu, Yasuhiro Togano, V. Wagner, P. Koseoglou, F. Flavigny, J. M. Gheller, Tomohiro Uesaka, A. Obertelli, Zs. Dombrádi, Hiroyoshi Sakurai, T. Motobayashi, Julien Gibelin, Dong-Wook Kim, O. Aktas, V. Lapoux, K. Yoshida, M. M. Juhász, Kamila Sieja, Zaihong Yang, I. Murray, K. I. Hahn, T. Kobayashi, X. X. Xu, Si-Ge Chen, P. A. Söderström, Victor Vaquero, Thomas Aumann, and C. Hilaire

Subjects
Physics, 010308 nuclear & particles physics, Island of inversion, 0103 physical sciences, Geophysics, 010306 general physics, 01 natural sciences
Published
2021

35. Corrigendum to 'Single-neutron knockout from 20C and the structure of 19C' [Phys. Lett. B 769 (2017) 503–508]

Author

J.W. Hwang, S. Kim, Y. Satou, N.A. Orr, Y. Kondo, T. Nakamura, J. Gibelin, N.L. Achouri, T. Aumann, H. Baba, F. Delaunay, P. Doornenbal, N. Fukuda, N. Inabe, T. Isobe, D. Kameda, D. Kanno, N. Kobayashi, T. Kobayashi, T. Kubo, S. Leblond, J. Lee, F.M. Marqués, R. Minakata, T. Motobayashi, D. Murai, T. Murakami, K. Muto, T. Nakashima, N. Nakatsuka, A. Navin, S. Nishi, S. Ogoshi, H. Otsu, H. Sato, Y. Shimizu, H. Suzuki, K. Takahashi, H. Takeda, S. Takeuchi, R. Tanaka, Y. Togano, A.G. Tuff, M. Vandebrouck, and K. Yoneda

Subjects
Physics, QC1-999
Published
2017
Full Text
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36. Quasifree Neutron Knockout Reaction Reveals a Small s -Orbital Component in the Borromean Nucleus B17

Author

Shuichi Ota, V. Panin, A. Ohkura, Toshiyuki Sumikama, Y. Kiyokawa, Takashi Nakamura, J. Yasuda, T. Isobe, S. Kawakami, Y. Kanaya, Ji Feng, H. Sato, A. Giganon, K. Hasegawa, D. Kim, C. Caesar, Toshio Kobayashi, K. Yoneda, Masanori Dozono, Noritsugu Nakatsuka, Motoki Kobayashi, Juzo Zenihiro, Atsumi Saito, Tsuyoshi Miyazaki, Shoko Koyama, J.-Y. Roussé, Y.L. Sun, Z. Korkulu, Nagao Kobayashi, C. Santamaria, Y. Shindo, Stefanos Paschalis, F. Flavigny, Nicolas Michel, E. C. Pollacco, Yasuhiro Togano, A. Corsi, Yukie Maeda, C. X. Yuan, N. A. Orr, L. Stuhl, Hideaki Otsu, Shan-Gui Zhou, D. Calvet, Tomohiro Uesaka, F. M. Marqués, A. Delbart, G. Authelet, J. M. Gheller, M. Sako, Yohei Shimizu, Yuya Kubota, A. Gillibert, Y. Nishio, T. Ozaki, S. Reichert, J. Tsubota, Kazuyuki Ogata, Wei Zuo, Zaihong Yang, M. Shikata, K. Yoshida, Qiang Yuan, J. Gibelin, V. Lapoux, Masaki Sasano, H. Baba, Furong Xu, A. Obertelli, Masaaki Kimura, Xianping Sun, Yosuke Kondo, M. Tabata, T. Motobayashi, Satoshi Sakaguchi, and J. G. Li

Subjects
Physics, Component (thermodynamics), Nuclear Theory, General Physics and Astronomy, 01 natural sciences, Momentum, Nuclear physics, Atomic orbital, Borromean nucleus, 0103 physical sciences, Neutron, Continuum (set theory), Halo, 010306 general physics, Astrophysics::Galaxy Astrophysics
Abstract

A kinematically complete quasifree (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 a 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 a neutron halo.

Published
2021

37. Shape Changes in the Mirror Nuclei Kr70 and Se70

Author

B. Blank, E. Sahin, D. T. Doherty, W. Korten, A. Obertelli, A. Boso, Tomás R. Rodríguez, Hiroyoshi Sakurai, P. Doornenbal, T. Motobayashi, D. G. Jenkins, David Steppenbeck, G. de Angelis, J. Gerl, Roman Gernhäuser, J. Libert, P. Aguilera, J. P. Delaroche, L. Sinclair, Alejandro Algora, P. J. Davies, Michel Girod, T. Saito, D. Lubos, Toshiaki Ando, Ryo Taniuchi, Si-Ge Chen, M. Zielińska, S. Nagamine, H. Baba, R. Wadsworth, Berta Rubio, Shoko Koyama, A. Corsi, Kathrin Wimmer, Megumi Niikura, and T. Arici

Subjects
Physics, Nuclear Theory, Nuclear structure, Stochastic matrix, General Physics and Astronomy, Order (ring theory), Inelastic scattering, 01 natural sciences, Matrix (mathematics), Isospin, 0103 physical sciences, Mirror nuclei, Atomic physics, Anomaly (physics), Nuclear Experiment, 010306 general physics
Abstract

We studied the proton-rich T_{z}=-1 nucleus ^{70}Kr through inelastic scattering at intermediate energies in order to extract the reduced transition probability, B(E2;0^{+}→2^{+}). Comparison with the other members of the A=70 isospin triplet, ^{70}Br and ^{70}Se, studied in the same experiment, shows a 3σ deviation from the expected linearity of the electromagnetic matrix elements as a function of T_{z}. At present, no established nuclear structure theory can describe this observed deviation quantitatively. This is the first violation of isospin symmetry at this level observed in the transition matrix elements. A heuristic approach may explain the anomaly by a shape change between the mirror nuclei ^{70}Kr and ^{70}Se contrary to the model predictions.

Published
2021

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

Author

Z H, Yang, Y, Kubota, A, Corsi, K, Yoshida, X-X, Sun, J G, Li, M, Kimura, N, Michel, K, Ogata, C X, Yuan, Q, Yuan, G, Authelet, H, Baba, C, Caesar, D, Calvet, A, Delbart, M, Dozono, J, Feng, F, Flavigny, J-M, Gheller, J, Gibelin, A, Giganon, A, Gillibert, K, Hasegawa, T, Isobe, Y, Kanaya, S, Kawakami, D, Kim, Y, Kiyokawa, M, Kobayashi, N, Kobayashi, T, Kobayashi, Y, Kondo, Z, Korkulu, S, Koyama, V, Lapoux, Y, Maeda, F M, Marqués, T, Motobayashi, T, Miyazaki, T, Nakamura, N, Nakatsuka, Y, Nishio, A, Obertelli, A, Ohkura, N A, Orr, S, Ota, H, Otsu, T, Ozaki, V, Panin, S, Paschalis, E C, Pollacco, S, Reichert, J-Y, Roussé, A T, Saito, S, Sakaguchi, M, Sako, C, Santamaria, M, Sasano, H, Sato, M, Shikata, Y, Shimizu, Y, Shindo, L, Stuhl, T, Sumikama, Y L, Sun, M, Tabata, Y, Togano, J, Tsubota, F R, Xu, J, Yasuda, K, Yoneda, J, Zenihiro, S-G, Zhou, W, Zuo, T, Uesaka, Département de Physique Nucléaire (ex SPhN) (DPHN), Institut de Recherches sur les lois Fondamentales de l'Univers (IRFU), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay, Institut de Physique Nucléaire d'Orsay (IPNO), Centre National de la Recherche Scientifique (CNRS)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Paris-Sud - Paris 11 (UP11), Laboratoire de physique corpusculaire de Caen (LPCC), Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Normandie Université (NU)-École Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN), Normandie Université (NU)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3), Université Paris-Sud - Paris 11 (UP11)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), and Normandie Université (NU)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS)

Subjects
Nuclear Theory, FOS: Physical sciences, Astrophysics::Cosmology and Extragalactic Astrophysics, [PHYS.NEXP]Physics [physics]/Nuclear Experiment [nucl-ex], Nuclear Experiment (nucl-ex), Nuclear Experiment, Astrophysics::Galaxy Astrophysics, Nuclear Physics
Abstract

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., Accepted for publication in Physical Review Letters,8 pages, 4 figures

Published
2021

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

Author

Zs. Dombradi, S. Y. Park, T. Isobe, F. Browne, K. Moschner, Thomas Aumann, R.-B. Gerst, F. Château, Kathrin Wimmer, X. X. Xu, Z. Elekes, L. Zanetti, Hideaki Otsu, B. D. Linh, Hirofumi Yamada, Si-Ge Chen, P. A. Söderström, Yutaka Utsuno, Igor Gašparić, H. N. Liu, Jenny Lee, Zaihong Yang, I. Murray, Yasuhiro Togano, F. Flavigny, K. I. Hahn, L. Stuhl, Yuya Kubota, V. Wagner, Tomohiro Uesaka, A. Giganon, D. Kim, M. MacCormick, C. Lehr, V. Panin, L. X. Chung, P. Koseoglou, T. Lokotko, Y.L. Sun, E. Sahin, K. Yoneda, Victor Vaquero, M. L. Cortés, Takashi Nakamura, S. Franchoo, P. Doornenbal, Satoshi Takeuchi, Masahiro Yasuda, O. Aktas, A. Gillibert, V. Lapoux, Nobuyuki Chiga, Takaharu Otsuka, T. Koiwai, Hiroyoshi Sakurai, T. Motobayashi, M. M. Juhász, Kazuki Yoshida, David Steppenbeck, Julien Gibelin, H. Törnqvist, Toshio Kobayashi, Kazuyuki Ogata, W. Rodriguez, N. L. Achouri, C. Hilaire, S. Wang, Donghang Yan, N. Paul, A. Obertelli, J. M. Gheller, Yosuke Kondo, V. Werner, D. Calvet, D. M. Rossi, Masaki Sasano, H. Baba, D. Sohler, A. Corsi, A. Delbart, Institut de Recherches sur les lois Fondamentales de l'Univers (IRFU), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay, Institut de Physique Nucléaire d'Orsay (IPNO), Centre National de la Recherche Scientifique (CNRS)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Paris-Sud - Paris 11 (UP11), Laboratoire de physique corpusculaire de Caen (LPCC), Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Normandie Université (NU)-École Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN), Normandie Université (NU)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3), Université Paris-Sud - Paris 11 (UP11)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), Normandie Université (NU)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), RIKEN Nishina Center for Accelerator-Based Science, European Research Council, European Commission, Helmholtz International Center for FAIR, German Research Foundation, Alexander von Humboldt Foundation, Ministry of Science and Technology of Vietnam, Government of South Korea, Agencia Estatal de Investigación (España), Federal Ministry of Education and Research (Germany), Helmholtz Graduate School for Hadron and Ion Research, and National Research, Development and Innovation Office (Hungary)

Subjects
Nuclear and High Energy Physics, Shell closure, γ -ray spectroscopy, [PHYS.NEXP]Physics [physics]/Nuclear Experiment [nucl-ex], 01 natural sciences, 0103 physical sciences, Bound state, nuclear shell model, proton knock-out reaction, gamma-ray spectroscopy, invariant-mass method, radioactive beams, Invariant mass, Neutron, ddc:530, Nuclear structure, 010306 general physics, Spectroscopy, Physics, Valence (chemistry), Proton knock-out reaction, 010308 nuclear & particles physics, Invariant mass method, Isotopes of argon, lcsh:QC1-999, Excited state, γ-ray spectroscopy, Atomic physics, lcsh:Physics
Abstract

8 pags., 4 figs., 3 tabs., The nuclear structure of 51Ar, an uncharted territory so far, was studied by the (p,2p) reaction using γ-ray spectroscopy for the bound states and the invariant mass method for the unbound states. Two peaks were detected in the γ-ray spectrum and six peaks were observed in the 50Ar+n relative energy spectrum. Comparing the results to our shell-model calculations, two bound and six unbound states were established. Three of the unbound states could only be placed tentatively due to the low number of counts in the relative energy spectrum of events associated with the decay through the first excited state of 50Ar. The low cross sections populating the two bound states of 51Ar could be interpreted as a clear signature for the presence of significant subshell closures at neutron numbers 32 and 34 in argon isotopes. It was also revealed that due to the two valence holes, unbound collective states coexist with individual-particle states in 51Ar., We are very grateful to the RIKEN Nishina Center accelerator staff for providing the stable beam and to the BigRIPS team for the smooth operation of the secondary beams. The development of the MINOS device has been supported by the European Research Council through the ERC Grant No. MINOS-258567. F. B. was supported by the RIKEN Special Postdoctoral Researcher Program. K. O. acknowledges the support by Grant-in-Aid for Scientific Research JP16K05352. Y. U. acknowledges the support by Grant-in-Aid for Scientific Research 20K03981. Y. L. S. acknowledges the support of Marie Skłodowska-Curie Individual Fellowship (H2020-MSCA-IF-2015-705023) from the European Union and the support from the Helmholtz International Center for FAIR. H. N. L. acknowledges the support from the Enhanced Eurotalents program (PCOFUND-GA-2013-600382) co-funded by CEA and the European Union. T. A., C. L., D. R., H. T., V. W., L. Z., H. N. L., V. W. and A. O. acknowledge the support from the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) Project No. 279384907-SFB 1245. R. B. G. acknowledges the support from the DFG under Grant No. BL 1513/1-1. Y. L. S. and A. O. acknowledge the support from the Alexander von Humboldt Foundation. B. D. L. and L. X. C. acknowledge the support from the Vietnam Ministry of Science and Technology under Grant No. ĐTCB.01/21/VKHKTHN. I. G. has been supported by HIC for FAIR and HRZZ under project No. 1257 and 7194. K. I. H., D. K. and S. Y. P. acknowledge the support from the NRF grant funded by the Korea government (No. 2017R1A2B2012382 and 2019M7A1A1033186). F. B. acknowledge the support from the RIKEN Special Postdoctoral Researcher Program. D. S. and Z. E. were supported by projects No. GINOP-2.3.3-15-2016-00034 and No. K128947. V. V. acknowledges support from the Spanish Ministerio de Economía y Competitividad under Contract No. FPA2017-84756-C4-2-P. V. W. and P. K. acknowledge the support from BMBF grants 05P15RDFN1 and 05P19RDFN1. P. K. acknowledges support from HGS-HIRe. This work was also supported by NKFIH (114454).

Published
2021

40. Three-body breakup of $^6$He and its halo structure

Author

Yuichi Ichikawa, K. Yoneda, Hiroyoshi Sakurai, T. Shinohara, T. Motobayashi, T. Shimamura, Y. Satou, T. Kobayshi, Y.L. Sun, Nori Aoi, Kazuyuki Ogata, Y. Kikuchi, Takashi Nakamura, Takuma Matsumoto, Takashi Sugimoto, Masamichi Ishihara, Kazuo Ieki, Yasuhiro Togano, Hideaki Otsu, Satoshi Takeuchi, Jenny Lee, Yosuke Kondo, Susumu Shimoura, Département de Physique Nucléaire (ex SPhN) (DPHN), Institut de Recherches sur les lois Fondamentales de l'Univers (IRFU), and Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay

Subjects
Nuclear and High Energy Physics, Nuclear Theory, Halo nucleus, [PHYS.NEXP]Physics [physics]/Nuclear Experiment [nucl-ex], 7. Clean energy, 01 natural sciences, Nuclear breakup, Nuclear physics, [formula omitted])X, 0103 physical sciences, Halo nuclei, Coulomb, Electric dipole response, Coulomb breakup, Neutron, 010306 general physics, Nuclear Experiment, Physics, 12 C( 6 He, Range (particle radiation), 208 Pb( 6 He, 010308 nuclear & particles physics, Scattering, 12C(6He, α+2n)X, Breakup, 208Pb(6He, lcsh:QC1-999, α+2n )X, Halo, Nucleon, 12C(6He, 208Pb(6He, α+2n)X, lcsh:Physics
Abstract

The Borromean halo nucleus 6He has been studied by a kinematically complete measurement of Coulomb and nuclear breakup into α + 2n on Pb and C targets at 70 MeV/nucleon. Fully quantum-mechanical four-body breakup calculations reproduce the energy and angular differential cross sections below E rel ∼ 1 MeV for both targets. The model used here reproduces the 6He ground-state properties as well as α-n and n-n scattering data and predicts an average opening angle 〈 θ n n 〉 of 68∘ between the two halo neutrons. However, the model underestimates the breakup cross sections for higher E rel , indicating a possible contribution from the inelastic breakup. Alternatively, we examine the empirically modified calculations that reproduce the energy-differential cross sections for a wide range of scattering angles for both targets. The extracted B(E1) peaks at E rel ∼ 1.4 MeV and amounts to 1.6(2) e2 fm2 for E rel ≤ 20 MeV, resulting 〈 θ n n 〉 = 56 − 10 + 9 degrees. In either interpretation, the current results show evidence of the dineutron spatial correlation in 6He.

Published
2021

41. N=32 shell closure below calcium: Low-lying structure of Ar50

Author

Nobuyuki Chiga, K. Moschner, T. Koiwai, Hiroyoshi Sakurai, V. Lapoux, A. Gillibert, Yutaka Utsuno, D. Calvet, T. Isobe, Kathrin Wimmer, T. Motobayashi, Jenny Lee, Achim Schwenk, H. Toernqvist, Yuya Kubota, Victor Vaquero, R.-B. Gerst, F. Château, W. Rodriguez, N. Shimizu, B. D. Linh, D. M. Rossi, Masahiro Yasuda, Tomohiro Uesaka, Hideaki Otsu, Igor Gašparić, H. N. Liu, V. Panin, H. Baba, Kazuyuki Ogata, L. X. Chung, S. Y. Park, Julien Gibelin, Hirofumi Yamada, K. Yoshida, C. Lehr, Duo Yan, L. Achouri, Zaihong Yang, L. Stuhl, A. Giganon, I. Murray, S. Wang, N. Paul, L. Zanetti, E. Sahin, Y. L. Sun, J. Simonis, A. Obertelli, K. Yoneda, C. Hilaire, K. I. Hahn, V. Werner, David Steppenbeck, Jason D. Holt, P. Doornenbal, A. Delbart, M. MacCormick, P. Koseoglou, J. M. Gheller, Alessandra Corsi, Thomas Aumann, Masaki Sasano, Dóra Sohler, Satoshi Takeuchi, M. L. Cortés, S. Franchoo, T. Kobayashi, F. Flavigny, X. X. Xu, Si-Ge Chen, P. A. Söderström, Dong-Wook Kim, F. Browne, O. Aktas, Yosuke Kondo, Yasuhiro Togano, T. Lokotko, Takashi Nakamura, Javier Fernandez Menendez, and V. Wagner

Subjects
Physics, 010308 nuclear & particles physics, 0103 physical sciences, Closure (topology), Shell (structure), Calcium low, 010306 general physics, 01 natural sciences, Molecular physics
Published
2020

42. Surface Localization of the Dineutron in Li11

Author

V. Lapoux, Nagao Kobayashi, Stefanos Paschalis, A. Ohkura, C. Caesar, Atsumi Saito, K. Yoneda, Masanori Dozono, Y. L. Sun, A. Obertelli, J. Tsubota, Zaihong Yang, Yohei Shimizu, M. Shikata, H. Baba, Masaki Sasano, L. Stuhl, Y. Kikuchi, T. Ozaki, F. M. Marqués, J. Yasuda, Toshio Kobayashi, V. Panin, S. Reichert, M. Tabata, Noritsugu Nakatsuka, G. Authelet, T. Motobayashi, C. Santamaria, D. Calvet, Juzo Zenihiro, N. A. Orr, T. Isobe, E. C. Pollacco, Tomohiro Uesaka, Yuya Kubota, J. M. Gheller, A. Gillibert, Motoki Kobayashi, Shoko Koyama, Hideaki Otsu, Toshiyuki Sumikama, K. Hasegawa, Z. Korkulu, Julien Gibelin, Y. Kiyokawa, Yosuke Kondo, M. Sako, A. Corsi, Satoshi Sakaguchi, A. Giganon, Y. Nishio, A. Delbart, S. Kawakami, Shuichi Ota, F. Flavigny, Yukie Maeda, Takashi Nakamura, Ji Feng, H. Sato, J.-Y. Roussé, Yasuhiro Togano, Kazuyuki Ogata, D. Kim, Y. Kanaya, Tsuyoshi Miyazaki, and Y. Shindo

Subjects
Surface (mathematics), Physics, Nuclear Theory, General Physics and Astronomy, Nuclear matter, 7. Clean energy, 01 natural sciences, Nuclear physics, Momentum, medicine.anatomical_structure, 0103 physical sciences, medicine, Neutron, Nuclear Experiment, 010306 general physics, Nucleon, Nucleus
Abstract

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.

Published
2020

43. Transition strengths in the neutron-rich Ni73,74,75 isotopes

Author

P. A. Söderström, T. Furumoto, K. Kaneko, D. Mengoni, J. J. Valiente-Dobón, K. Matsui, István Kuti, Nunzio Itaco, Yoshiaki Shiga, Zhengyu Xu, G. de Angelis, F. Browne, Dóra Sohler, S. Ceruti, A. Gargano, Zs. Vajta, D. R. Napoli, Rin Yokoyama, M. Yalcinkaya, L. Coraggio, Satoshi Takeuchi, H. Liu, R. Orlandi, V. Modamio-Hoybjor, Jinguang Wu, E. Sahin, L. Sinclair, Ryo Taniuchi, F. L. Bello Garrote, F. C. L. Crespi, T. Isobe, G. Benzoni, P. Doornenbal, Stephen Rice, A. Gottardo, Jenny Lee, Satoru Momiyama, Hiroshi Watanabe, D. Fang, Giuseppe Lorusso, Hiroyoshi Sakurai, Jan Taprogge, M. C. Delattre, Masafumi Matsushita, R. Avigo, Megumi Niikura, T. Motobayashi, B. Melon, O. Wieland, R. Daido, Zs. Dombrádi, H. Wang, N. Blasi, H. Baba, Toshiyuki Sumikama, Z. Patel, Shunji Nishimura, Tsuyoshi Miyazaki, and P. Van Isacker

Subjects
Physics, Proton, Isotope, 010308 nuclear & particles physics, Shell (structure), Coulomb excitation, 01 natural sciences, medicine.anatomical_structure, 0103 physical sciences, medicine, Neutron, Atomic physics, 010306 general physics, Nucleus, Excitation, Line (formation)
Abstract

Reduced transition probabilities have been measured for the neutron-rich Ni73,74,75 nuclei with relativistic Coulomb excitation performed at the RIKEN Nishina Center. For the even-even Ni isotope the determined B(E2;0+→2+) value is compatible within errors with the result of a previous intermediate energy Coulomb excitation experiment, although being somewhat larger. For the odd Ni isotopes B(E2) values have been determined for the first time. In the middle νg9/2 shell nucleus Ni73 three peak candidates have been observed and tentatively assigned to the (5/2+), (13/2+), and (11/2+) excitations. Two peak candidates have been observed in Ni75 and tentatively assigned to the (13/2+) and (11/2+) levels. The measured B(E2) values are in line with the large B(E2) reported in Ni70 and at variance with the small strength measured in Ni72. Excitation energies compare well with the result of large-scale shell-model calculations, while B(E2) values are larger than predicted. This could indicate an increasing contribution of proton excitations across the Z=28 shell closure when approaching Ni78.

Published
2020

44. Sequential Nature of (p,3p) Two-Proton Knockout from Neutron-Rich Nuclei

Author

Megumi Niikura, K. Yoneda, Tomohiro Uesaka, T. Miyazaki, J.-Y. Roussé, A. Jungclaus, I. G. Stefan, Masaki Sasano, A. Gillibert, Jian Liu, Hiroyoshi Sakurai, David Steppenbeck, Zs. Dombradi, K. Moschner, M. Gómez-Ramos, Satoshi Takeuchi, D. Calvet, T. Isobe, Shunji Nishimura, T. Saito, V. Lapoux, H. Wang, T. Motobayashi, L. Olivier, R. Lozeva, A. Gottardo, S. Franchoo, C. Péron, H. Baba, Jinguang Wu, G. Authelet, A. Delbart, A. Blazhev, J. M. Gheller, Hideaki Otsu, F. Château, Masafumi Matsushita, Zs. Vajta, Zena Patel, Victor Vaquero, Kathrin Wimmer, M. L. Cortés, K. Matsui, Shuichi Ota, C. Santamaria, E. C. Pollacco, M. Dewald, Alessandra Corsi, F. Browne, C. R. Nita, M. Rudigier, Z. Korkulu, Jenny Lee, Yoshiaki Shiga, K. Hadynska-Klek, S. Nagamine, Satoru Momiyama, A. Frotscher, T. Arici, Ryo Taniuchi, Noritaka Shimizu, C. R. Nobs, Toshiyuki Sumikama, Alison Bruce, C. Louchart, E. Sahin, Toshiaki Ando, Zhenci Xu, F. Giacoppo, Y. Kubota, L. X. Chung, B. D. Linh, P. Doornenbal, F. Flavigny, A. Giganon, N. Paul, C. M. Shand, Noritsugu Nakatsuka, Zi Hong Liu, V. Werner, M. Górska, Si-Ge Chen, P. A. Söderström, D. Suzuki, M. Lettmann, R. Orlandi, C. Lizarazo, A. Obertelli, Raymond J. Carroll, Bing Ding, Zs. Podolyák, Shoko Koyama, and Alan Peyaud

Subjects
Physics, Hydrogen, Proton, Projectile, Nuclear Theory, General Physics and Astronomy, chemistry.chemical_element, 01 natural sciences, Coincidence, Nuclear physics, medicine.anatomical_structure, chemistry, MINOS, 0103 physical sciences, medicine, Neutron, Nuclear Experiment, 010306 general physics, Nucleon, Nucleus
Abstract

Twenty-one two-proton knockout (p; 3p) cross sections from neutron-rich nuclei at ~ 250 MeV/nucleon were measured. For the first time, the angular distribution of the three emitted protons were measured in coincidence with the tracker and hydrogen target MINOS, demonstrating that the (p; 3p) kinematics is consistent with two sequential proton-proton collisions within the projectile nucleus. Ratios of (p; 3p) over (p; 2p) inclusive cross sections follow the trend of other many-proton (neutron) removal reactions, further reinforcing the sequential nature of (p; 3p) in neutron-rich nuclei.

Published
2020

45. Metastable States of Se92,94 : Identification of an Oblate K Isomer of Se94 and the Ground-State Shape Transition between N=58 and 60

Author

L. Olivier, I. Kojouharov, G. Authelet, J. M. Gheller, V. Lapoux, Jenny Lee, J.-Y. Roussé, J. Gerl, C. Lizarazo, N. Paul, Noritsugu Nakatsuka, Hiroyoshi Sakurai, H. Schaffner, P. M. Walker, Zi Hong Liu, V. Werner, David Steppenbeck, T. Motobayashi, A. Blazhev, P. Doornenbal, Shunji Nishimura, I. Stefan, M. L. Cortés, T. Arici, J. J. Liu, Tomás R. Rodríguez, Alison Bruce, A. Giganon, C. Santamaria, F. Château, Megumi Niikura, Zhengyu Xu, F. Browne, Tomohiro Uesaka, M. Rudigier, C. R. Niţă, P. A. Söderström, Zena Patel, T. Saito, N. Kurz, M. Górska, S. Franchoo, A. Gillibert, G. X. Dong, A. Gottardo, C. M. Shand, Satoru Momiyama, L. X. Chung, C. R. Nobs, B. D. Linh, S. Nagamine, Ryo Taniuchi, A. Obertelli, M. Dewald, K. Moschner, Kathrin Wimmer, H. Baba, R. J. Caroll, D. Calvet, F. Flavigny, Bing Ding, Zs. Podolyák, Furong Xu, Toshiaki Ando, Si-Ge Chen, Victor Vaquero, M. Lettmann, A. Corsi, Norbert Pietralla, and A. Delbart

Subjects
Physics, 010308 nuclear & particles physics, General Physics and Astronomy, chemistry.chemical_element, Germanium, 01 natural sciences, Hafnium, medicine.anatomical_structure, chemistry, Atomic orbital, Metastability, 0103 physical sciences, Physics::Atomic and Molecular Clusters, medicine, Neutron, Atomic physics, Nuclear Experiment, 010306 general physics, Ground state, Spectroscopy, Nucleus
Abstract

Here we present new information on the shape evolution of the very neutron-rich ^{92,94}Se nuclei from an isomer-decay spectroscopy experiment at the Radioactive Isotope Beam Factory at RIKEN. High-resolution germanium detectors were used to identify delayed γ rays emitted following the decay of their isomers. New transitions are reported extending the previously known level schemes. The isomeric levels are interpreted as originating from high-K quasineutron states with an oblate deformation of β∼0.25, with the high-K state in ^{94}Se being metastable and K hindered. Following this, ^{94}Se is the lowest-mass neutron-rich nucleus known to date with such a substantial K hindrance. Furthermore, it is the first observation of an oblate K isomer in a deformed nucleus. This opens up the possibility for a new region of K isomers at low Z and at oblate deformation, involving the same neutron orbitals as the prolate orbitals within the classic Z∼72 deformed hafnium region. From an interpretation of the level scheme guided by theoretical calculations, an oblate deformation is also suggested for the ^{94}Se_{60} ground-state band.

Published
2020

46. Halo Structure of the Neutron-Dripline Nucleus B19

Author

K. J. Cook, T. Kobayashi, S. K. Kim, H. Baba, T. Motobayashi, T. Murakami, S. Leblond, Takashi Nakamura, Yosuke Kondo, Hiroyuki Takeda, Ryuki Tanaka, Julien Gibelin, Noritsugu Nakatsuka, Hideaki Otsu, D. Kameda, K. Yoneda, Satoshi Takeuchi, Toshiyuki Kubo, Y. Satou, Kazuyuki Ogata, T. Isobe, Thomas Aumann, N. L. Achouri, Atsumi Saito, Nagao Kobayashi, T. Nakashima, S. Nishi, J. Lee, D. Kanno, Kouichi Hagino, S. Ogoshi, Q. Deshayes, K. Takahashi, Yohei Shimizu, Yasuhiro Togano, Daichi Murai, A. G. Tuff, K. Muto, H. Suzuki, Marine Vandebrouck, Franck Delaunay, F. M. Marqués, H. Sato, P. Doornenbal, Jongwon Hwang, A. Navin, Naoki Fukuda, N. A. Orr, J. Tsubota, Naohito Inabe, and R. Minakata

Subjects
Physics, Valence (chemistry), Isotope, Nuclear Theory, General Physics and Astronomy, 01 natural sciences, Dipole, 0103 physical sciences, Coulomb, Neutron, Halo, Atomic physics, Nuclear Experiment, 010306 general physics, Nucleon, Excitation
Abstract

The heaviest bound isotope of boron ^{19}B has been investigated using exclusive measurements of its Coulomb dissociation, into ^{17}B and two neutrons, in collisions with Pb at 220 MeV/nucleon. Enhanced electric dipole (E1) strength is observed just above the two-neutron decay threshold with an integrated E1 strength of B(E1)=1.64±0.06(stat)±0.12(sys) e^{2} fm^{2} for relative energies below 6 MeV. This feature, known as a soft E1 excitation, provides the first firm evidence that ^{19}B has a prominent two-neutron halo. Three-body calculations that reproduce the energy spectrum indicate that the valence neutrons have a significant s-wave configuration and exhibit a dineutronlike correlation.

Published
2020

47. Metastable States of ^{92,94}Se: Identification of an Oblate K Isomer of ^{94}Se and the Ground-State Shape Transition between N=58 and 60

Author

C, Lizarazo, P-A, Söderström, V, Werner, N, Pietralla, P M, Walker, G X, Dong, F R, Xu, T R, Rodríguez, F, Browne, P, Doornenbal, S, Nishimura, C R, Niţă, A, Obertelli, T, Ando, T, Arici, G, Authelet, H, Baba, A, Blazhev, A M, Bruce, D, Calvet, R J, Caroll, F, Château, S, Chen, L X, Chung, A, Corsi, M L, Cortés, A, Delbart, M, Dewald, B, Ding, F, Flavigny, S, Franchoo, J, Gerl, J-M, Gheller, A, Giganon, A, Gillibert, M, Górska, A, Gottardo, I, Kojouharov, N, Kurz, V, Lapoux, J, Lee, M, Lettmann, B D, Linh, J J, Liu, Z, Liu, S, Momiyama, K, Moschner, T, Motobayashi, S, Nagamine, N, Nakatsuka, M, Niikura, C, Nobs, L, Olivier, Z, Patel, N, Paul, Zs, Podolyák, J-Y, Roussé, M, Rudigier, T Y, Saito, H, Sakurai, C, Santamaria, H, Schaffner, C, Shand, I, Stefan, D, Steppenbeck, R, Taniuchi, T, Uesaka, V, Vaquero, K, Wimmer, and Z, Xu

Abstract

Here we present new information on the shape evolution of the very neutron-rich ^{92,94}Se nuclei from an isomer-decay spectroscopy experiment at the Radioactive Isotope Beam Factory at RIKEN. High-resolution germanium detectors were used to identify delayed γ rays emitted following the decay of their isomers. New transitions are reported extending the previously known level schemes. The isomeric levels are interpreted as originating from high-K quasineutron states with an oblate deformation of β∼0.25, with the high-K state in ^{94}Se being metastable and K hindered. Following this, ^{94}Se is the lowest-mass neutron-rich nucleus known to date with such a substantial K hindrance. Furthermore, it is the first observation of an oblate K isomer in a deformed nucleus. This opens up the possibility for a new region of K isomers at low Z and at oblate deformation, involving the same neutron orbitals as the prolate orbitals within the classic Z∼72 deformed hafnium region. From an interpretation of the level scheme guided by theoretical calculations, an oblate deformation is also suggested for the ^{94}Se_{60} ground-state band.

Published
2020

48. Shell structure of the neutron-rich isotopes Co69,71,73

Author

M. Lettmann, A. Gillibert, Alessandra Corsi, David Steppenbeck, S. Leblond, Yoshiaki Shiga, K. Yoshida, Toshiyuki Sumikama, Ryo Taniuchi, A. Gottardo, F. Nowacki, Jenny Lee, V. Lapoux, Yuya Kubota, C. Péron, A. Delbart, Shunji Nishimura, G. Authelet, Si-Ge Chen, P. A. Söderström, C. Louchart, J. M. Gheller, T. Miyazaki, Alan Peyaud, C. M. Shand, Satoshi Takeuchi, Masafumi Matsushita, F. Giacoppo, H. Baba, Satoru Momiyama, S. Franchoo, E. Sahin, Zhenci Xu, Jinguang Wu, Shuichi Ota, V. Werner, Hideaki Otsu, Alfredo Poves, L. X. Chung, Megumi Niikura, C. Santamaria, Tomohiro Uesaka, I. Stefan, K. Matsui, P. Doornenbal, Kazuyuki Ogata, F. Browne, Masaki Sasano, Zs. Dombrádi, Shoko Koyama, Z. Korkulu, Zs. Vajta, K. Hadynska-Klek, T. Lokotko, Z. Patel, L. Olivier, H. Wang, R. Lozeva, A. Obertelli, Hiroyoshi Sakurai, T. Motobayashi, E. C. Pollacco, J.-Y. Roussé, D. Calvet, T. Isobe, F. Château, and Daisuke Suzuki

Subjects
Physics, Isotope, 010308 nuclear & particles physics, Nuclear structure, Impulse (physics), 7. Clean energy, 01 natural sciences, Coincidence, Nuclear physics, MINOS, 0103 physical sciences, Neutron, Detector array, Nuclear Experiment, 010306 general physics, Excitation
Abstract

The structures of the neutron-rich Co69,71,73 isotopes were investigated via (p,2p) knockout reactions at the Radioactive Isotope Beam Factory, RIKEN. Isotopes of interest were studied using the DALI2 γ-ray detector array combined with the MINOS target and tracker system. Level schemes were reconstructed using the γ-γ coincidence technique, with tentative spin-parity assignments based on the measured inclusive and exclusive cross sections. Comparison with shell-model calculations using the Lenzi-Nowacki-Poves-Sieja LNPS and PFSDG-U interactions suggests coexistence of spherical and deformed shapes at low excitation energies in the Co69,71,73 isotopes. The distorted-wave impulse approximation (DWIA) framework was used to calculate the single-particle cross sections. These values were compared with the experimental findings.

Published
2020

49. Fragmentation of Single-Particle Strength around the Doubly Magic Nucleus Sn132 and the Position of the 0f5/2 Proton-Hole State in In131

Author

Hiroyoshi Sakurai, J. Tscheuschner, Yosuke Kondo, A. Bracco, D. Semmler, S. Nishimura, T. Motobayashi, Ryo Taniuchi, N. Imai, Kazuo Ieki, A. Jungclaus, Ismael Martel, F. Camera, P. Schrock, Heiko Scheit, Juzo Zenihiro, Andreas Zilges, V. Derya, D. S. Ahn, K. Boretzky, Yasuhiro Togano, R. Avigo, M.N. Harakeh, D. Symochko, Hiroyuki Takeda, T. Kubo, Shoko Koyama, D. M. Rossi, M. Shikata, H. Baba, Agnese Giaz, Haik Simon, T. Ozaki, J. L. Rodriguez-Sanchez, P. Doornenbal, David Steppenbeck, Atsumi Saito, I. Syndikus, C. Caesar, M. Heil, Si-Ge Chen, J. A. Tostevin, J. Tsubota, Nagao Kobayashi, Deniz Savran, Yoshiaki Shiga, U. Garg, Marina Petri, N. Nakatsuka, Masafumi Matsushita, Toshiyuki Sumikama, Naohito Inabe, Victor Vaquero, Takashi Nakamura, B. Million, J. Endres, Satoshi Takeuchi, A. Horvat, Y. Shimizu, E. V. Litvinova, K. Yoneda, H. Suzuki, O. Wieland, Rene Reifarth, Hideaki Otsu, H. Wang, Fabia Schindler, Shuichi Ota, Nasser Kalantar-Nayestanaki, M. Nishimura, Thomas Aumann, and N. Fukuda

Subjects
Physics, medicine.anatomical_structure, Fragmentation (mass spectrometry), Astrophysics::High Energy Astrophysical Phenomena, Excited state, 0103 physical sciences, Magic (programming), medicine, General Physics and Astronomy, Atomic physics, 010306 general physics, 01 natural sciences, Nucleus
Abstract

Spectroscopic factors of neutron-hole and proton-hole states in 131Sn and 131In, respectively, were measured using one-nucleon removal reactions from doubly magic 132Sn at relativistic energies. For 131In, a 2910(50)-keV γ ray was observed for the first time and tentatively assigned to a decay from a 5=2− state at 3275(50) keV to the known 1=2− level at 365 keV. The spectroscopic factors determined for this new excited state and three other single-hole states provide first evidence for a strong fragmentation of singlehole strength in 131Sn and 131In. The experimental results are compared to theoretical calculations based on the relativistic particle-vibration coupling

Published
2020

50. Shell evolution of $N=40$ isotones towards $^{60}$Ca: First spectroscopy of $^{62}$Ti

Author

Masaki Sasano, S. M. Lenzi, Kazuki Yoshida, E. Sahin, V. Wagner, Hiroyoshi Sakurai, F. Nowacki, T. Isobe, W. Rodriguez, P. Doornenbal, Donghang Yan, D. Kim, T. Motobayashi, M.L. Cortés, Jason D. Holt, V. Lapoux, D. M. Rossi, Toshio Kobayashi, F. Flavigny, A. Giganon, B. D. Linh, F. Château, V. Panin, H. Baba, N. Paul, L. X. Chung, D. Calvet, X. X. Xu, David Steppenbeck, V. Werner, Igor Gašparić, H. N. Liu, A. Delbart, Yosuke Kondo, Si-Ge Chen, L. Achouri, Julien Gibelin, Tomohiro Uesaka, J. M. Gheller, A. Corsi, S. R. Stroberg, Alfredo Poves, Achim Schwenk, Satoshi Takeuchi, Thomas Aumann, R.-B. Gerst, C. Lehr, Jenny Lee, Yasuhiro Togano, C. Hilaire, Y.L. Sun, P. Koseoglou, Nobuyuki Chiga, K. Yoneda, F. Browne, Victor Vaquero, Yuya Kubota, T. Lokotko, T. Koiwai, Zaihong Yang, Takashi Nakamura, S. Wang, J. Simonis, I. Murray, Javier Fernandez Menendez, A. Obertelli, Kazuyuki Ogata, A. Gillibert, H. Toernqvist, M. MacCormick, Masahiro Yasuda, Hideaki Otsu, K. I. Hahn, L. Stuhl, O. Aktas, Hirofumi Yamada, Dóra Sohler, S. Franchoo, Tomás R. Rodríguez, L. Zanetti, K. Moschner, Kathrin Wimmer, S. Y. Park, P. A. Söderström, Institut de Recherches sur les lois Fondamentales de l'Univers (IRFU), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay, Institut Pluridisciplinaire Hubert Curien (IPHC), Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université de Strasbourg (UNISTRA)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de physique corpusculaire de Caen (LPCC), Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Normandie Université (NU)-École Nationale Supérieure d'Ingénieurs de Caen (ENSICAEN), Normandie Université (NU)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3), Institut de Physique Nucléaire d'Orsay (IPNO), Centre National de la Recherche Scientifique (CNRS)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Paris-Sud - Paris 11 (UP11), UAM. Departamento de Física Teórica, Université de Strasbourg (UNISTRA)-Centre National de la Recherche Scientifique (CNRS), Normandie Université (NU)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), Université Paris-Sud - Paris 11 (UP11)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), Université de Strasbourg (UNISTRA)-Université de Haute-Alsace (UHA) Mulhouse - Colmar (Université de Haute-Alsace (UHA))-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), RIKEN Nishina Center for Accelerator-Based Science, Japan Society for the Promotion of Science, Ministerio de Ciencia, Innovación y Universidades (España), Ministry of Science and Technology of Vietnam, Helmholtz International Center for FAIR, Croatian Science Foundation, National Research, Development and Innovation Office (Hungary), Ministerio de Economía y Competitividad (España), National Research Foundation of Korea, European Commission, Natural Sciences and Engineering Research Council of Canada, Federal Ministry of Education and Research (Germany), and National Research Council of Canada

Subjects
Nuclear and High Energy Physics, Nuclear Theory, Ab initio, FOS: Physical sciences, Shell evolution, [PHYS.NEXP]Physics [physics]/Nuclear Experiment [nucl-ex], 7. Clean energy, 01 natural sciences, Radioactive beams, Gamma-ray spectroscopy, Nuclear Theory (nucl-th), 0103 physical sciences, ddc:530, Nuclear Experiment (nucl-ex), 010306 general physics, Spectroscopy, Nuclear Experiment, Physics, 010308 nuclear & particles physics, Island of inversion, Isotone, Starke Wechselwirkung und exotische Kerne – Abteilung Blaum, Física, lcsh:QC1-999, Excited state, Quadrupole, Atomic physics, Nucleon, Ground state, lcsh:Physics
Abstract

7 pags., 4 figs., 1 tab., Excited states in the N=40 isotone Ti were populated via the V(p,2p)Ti reaction at ∼200 MeV/nucleon at the Radioactive Isotope Beam Factory and studied using γ-ray spectroscopy. The energies of the 2 →0 and 4 →2 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. The shell-model calculations for Ti show a dominant configuration with four neutrons excited across the N=40 gap. Likewise, they indicate that the N=40 island of inversion extends down to Z=20, disfavoring a possible doubly magic character of the elusive Ca., We thank the RIKEN Nishina Center accelerator staff and the Bi-gRIPS team for the stable operation of the high-intensity Zn beam and for the preparation of the secondary beam setting. K.O. ac-knowledges the support by Grant-in-Aid for Scientific Research of the Japan Society for the Promotion of Science (JSPS) JP16K05352. A.P. is supported in part by the Ministerio de Ciencia, Innovación y Universidades (Spain), Severo Ochoa Programme SEV-2016-0597 and grant PGC-2018-94583. F.B. is supported by the RIKEN Spe-cial Postdoctoral Researcher Program. L.X.C. and B.D.L. would like to thank the Vietnam Ministry of Science and Technology (MOST) for its support through the Physics Development Program Grant No. ÐTÐLCN.25/18. I.G. has been supported by HIC for FAIR and Croatian Science Foundation under projects no. 1257 and 7194. D. So. was supported by the the European Regional Develop-ment Fund contract No. GINOP-2.3.3-15-2016-00034 and the National Research, Development and Innovation Fund of Hungary via Project No. K128947. V.V. acknowledges support from the Span-ish Ministerio de Economía y Competitividad under Contract No. FPA2017-84756-C4-2-P. K.I.H., D.K. and S.Y.P. acknowledge the sup-port from the National Research Foundation of Korea grant No. 2018R1A5A1025563 and 2019M7A1A1033186. The development of MINOS was supported by the European Research Council through the ERC Grant No. MINOS-258567. This work was also supported by the JSPS KAKENHI Grant No. 18K03639, MEXT as “Priority is-sue on post-K computer” (Elucidation of the fundamental laws and evolution of the universe), the Joint Institute for Computational Fundamental Science (JICFuS), the CNS-RIKEN joint project for large-scale nuclear structure calculations, Natural Sciences and Engineering Research Council (NSERC) of Canada, the Deutsche Forschungsgemeinschaft – Projektnummer 279384907 – SFB 1245, the PRISMA Cluster of Excellence, and the BMBF under Contracts No. 05P18RDFN1 and 05P19RDFN1. TRIUMF receives funding via a contribution through the National Research Council Canada. Com-putations were performed at the Jülich Supercomputing Center (JURECA)

Published
2020

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