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1. 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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2. Intruder configurations in 29Ne at the transition into the island of inversion: Detailed structure study of 28Ne

Author

H. Wang, M. Yasuda, Y. Kondo, T. Nakamura, J.A. Tostevin, K. Ogata, T. Otsuka, A. Poves, N. Shimizu, K. Yoshida, N.L. Achouri, H. Al Falou, L. Atar, T. Aumann, H. Baba, K. Boretzky, C. Caesar, D. Calvet, H. Chae, N. Chiga, A. Corsi, H.L. Crawford, F. Delaunay, A. Delbart, Q. Deshayes, Zs. Dombrádi, C. Douma, Z. Elekes, P. Fallon, I. Gašparić, J.-M. Gheller, J. Gibelin, A. Gillibert, M.N. Harakeh, A. Hirayama, C.R. Hoffman, M. Holl, A. Horvat, Á. Horváth, J.W. Hwang, T. Isobe, J. Kahlbow, N. Kalantar-Nayestanaki, S. Kawase, S. Kim, K. Kisamori, T. Kobayashi, D. Körper, S. Koyama, I. Kuti, V. Lapoux, S. Lindberg, F.M. Marqués, S. Masuoka, J. Mayer, K. Miki, T. Murakami, M.A. Najafi, K. Nakano, N. Nakatsuka, T. Nilsson, A. Obertelli, N.A. Orr, H. Otsu, T. Ozaki, V. Panin, S. Paschalis, A. Revel, D. Rossi, A.T. Saito, T. Saito, M. Sasano, H. Sato, Y. Satou, H. Scheit, F. Schindler, P. Schrock, M. Shikata, Y. Shimizu, H. Simon, D. Sohler, O. Sorlin, L. Stuhl, S. Takeuchi, M. Tanaka, M. Thoennessen, H. Törnqvist, Y. Togano, T. Tomai, J. Tscheuschner, J. Tsubota, T. Uesaka, Z. Yang, and K. Yoneda

Subjects
In-beam γ-ray spectroscopy, Island of inversion, Shell evolution, Physics, QC1-999
Abstract

Detailed γ-ray spectroscopy of the exotic neon isotope 28Ne has been performed for the first time using the one-neutron removal reaction from 29Ne on a liquid hydrogen target at 240 MeV/nucleon. Based on an analysis of parallel momentum distributions, a level scheme with spin-parity assignments has been constructed for 28Ne and the negative-parity states are identified for the first time. The measured partial cross sections and momentum distributions reveal a significant intruder p-wave strength providing evidence of the breakdown of the N=20 and N=28 shell gaps. Only a weak, possible f-wave strength was observed to bound final states. Large-scale shell-model calculations with different effective interactions do not reproduce the large p-wave and small f-wave strength observed experimentally, indicating an ongoing challenge for a complete theoretical description of the transition into the island of inversion along the Ne isotopic chain.

Published
2023
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3. 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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4. Observation of a correlated free four-neutron system

Author

M. Duer, T. Aumann, R. Gernhäuser, V. Panin, S. Paschalis, D. M. Rossi, N. L. Achouri, D. Ahn, H. Baba, C. A. Bertulani, M. Böhmer, K. Boretzky, C. Caesar, N. Chiga, A. Corsi, D. Cortina-Gil, C. A. Douma, F. Dufter, Z. Elekes, J. Feng, B. Fernández-Domínguez, U. Forsberg, N. Fukuda, I. Gasparic, Z. Ge, J. M. Gheller, J. Gibelin, A. Gillibert, K. I. Hahn, Z. Halász, M. N. Harakeh, A. Hirayama, M. Holl, N. Inabe, T. Isobe, J. Kahlbow, N. Kalantar-Nayestanaki, D. Kim, S. Kim, T. Kobayashi, Y. Kondo, D. Körper, P. Koseoglou, Y. Kubota, I. Kuti, P. J. Li, C. Lehr, S. Lindberg, Y. Liu, F. M. Marqués, S. Masuoka, M. Matsumoto, J. Mayer, K. Miki, B. Monteagudo, T. Nakamura, T. Nilsson, A. Obertelli, N. A. Orr, H. Otsu, S. Y. Park, M. Parlog, P. M. Potlog, S. Reichert, A. Revel, A. T. Saito, M. Sasano, H. Scheit, F. Schindler, S. Shimoura, H. Simon, L. Stuhl, H. Suzuki, D. Symochko, H. Takeda, J. Tanaka, Y. Togano, T. Tomai, H. T. Törnqvist, J. Tscheuschner, T. Uesaka, V. Wagner, H. Yamada, B. Yang, L. Yang, Z. H. Yang, M. Yasuda, K. Yoneda, L. Zanetti, J. Zenihiro, M. V. Zhukov, 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), Institut de Recherches sur les lois Fondamentales de l'Univers (IRFU), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay, Grand Accélérateur National d'Ions Lourds (GANIL), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), Research unit Nuclear & Hadron Physics, and Nuclear Energy

Subjects
Multidisciplinary, Nuclear Force, Nuclear Structure, Tetraneutron, Reactions with Radioactive Beams, Physics, ddc:500, [PHYS.NEXP]Physics [physics]/Nuclear Experiment [nucl-ex]
Abstract

Nature 606(7915), 678 - 682 (2022). doi:10.1038/s41586-022-04827-6, Published by Nature Publ. Group, London [u.a.]

Published
2022
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5. Experimental Study of $^{4}n$ by Directly Detecting the Decay Neutrons

Author

Atsumi Saito, Yohei Shimizu, H. Törnqvist, B. Monteagudo, T. Isobe, M. Caamaño, H. Scheit, S. Kiyotake, J. Tscheuschner, M. L. Cortés, F. M. Marqués, N. Fukuda, N. A. Orr, J. M. Gheller, A. Gillibert, A. Matta, K. Yoneda, L. Stuhl, Z. Elekes, I. Kuti, V. Wagner, M. Miwa, Z. Halász, A. Obertelli, S. Kim, A. Revel, L. Zanetti, N. L. Achouri, S. Takeuchi, F. Dufter, C. A. Douma, S. Masuoka, Stefanos Paschalis, R. Gernhäuser, S. Chen, Nobuyuki Chiga, S. Storck, T. Shimada, M.N. Harakeh, P. Koseoglou, T. Harada, B. Yang, M. Matsumoto, H. Takeda, D. S. Ahn, Yuya Kubota, H. Yamada, Yasuhiro Togano, A. Hirayama, Y. Yasuda, T. Fujino, D. M. Rossi, Nasser Kalantar-Nayestanaki, J. Tanaka, M. Böhmer, N. Inabe, Didier Beaumel, S. Park, Thomas Aumann, H. Baba, Tomohiro Uesaka, F. Schindler, J. Feng, Zaihong Yang, I. Murray, Julien Gibelin, K. Boretzky, S. W. Huang, B. Fernández-Domínguez, S. Reichert, Takashi Nakamura, Yu-xin Liu, K. Wimmer, Yukie Maeda, L. Yang, H. Sato, E. Tronchin, P. Doornenbal, Dmytro Symochko, D. Cortina, J. Kahlbow, S. Shimoura, H. Suzuki, Hideaki Otsu, M. Potlog, P. J. Li, J. Mayer, H. Miki, Masaki Sasano, Toshio Kobayashi, Z. Ge, D. Kim, Juzo Zenihiro, T. Tomai, I. Stefan, M. Parlog, H. Simon, V. Panin, Igor Gašparić, C. Lehr, Yosuke Kondo, C. Lenain, U. Forsberg, 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), 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), Institut de Recherches sur les lois Fondamentales de l'Univers (IRFU), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay, Grand Accélérateur National d'Ions Lourds (GANIL), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), Normandie Université (NU)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3), 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), Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3), Research unit Nuclear & Hadron Physics, and Nuclear Energy

Subjects
Nuclear structure and force, tetraneutron, direct reactions, radioactive beams, Physics, Nuclear physics, 010308 nuclear & particles physics, 0103 physical sciences, Tetraneutron, Neutron, [PHYS.NEXP]Physics [physics]/Nuclear Experiment [nucl-ex], 010306 general physics, 01 natural sciences, Atomic and Molecular Physics, and Optics, 3. Good health
Abstract

The tetraneutron has attracted the attention of nuclear physicists during the past decades, but there is still no unambiguous confirmation of its existence or non-existence. A new experiment based on $$^{8}$$ He(p, 2p) $$^{7}$$ H{t+ $$^{4}n$$ } reaction, with direct detection of the four neutrons, has been carried out at RIBF, which can hopefully help to draw a definite conclusion on the tetraneutron system.

Published
2021
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6. Experimental study of 4 n with 8He(p,2p) reaction

Author

M. Böhmer, Masaki Sasano, S. Reichert, Naohito Inabe, S. Chen, T. Shimada, M. Matsumoto, Susumu Shimoura, I. Stefan, J. Kahlbow, N. Kalantar-Nayestanaki, T. Harada, D. Symochko, István Kuti, S. W. Huang, D. Cortina, Tomohiro Uesaka, Z. Ge, N. L. Achouri, Yosuke Kondo, Hiroyuki Takeda, K. Yoneda, B. Fernández-Domínguez, U. Forsberg, Z. Elekes, Roman Gernhäuser, Y. Yasuda, H. Suzuki, Yohei Shimizu, D. Beaumel, D. Kim, C. A. Douma, Yukie Maeda, A. Hirayama, J. M. Gheller, Heiko Scheit, F. Dufter, T. Elidiano, Yasuhiro Togano, M. L. Cortés, M. Potlog, Nobuyuki Chiga, P. J. Li, Juzo Zenihiro, B. Yang, T. Isobe, M. Caamaño, Thomas Aumann, H. T. Törnqvsit, A. Gillibert, D. S. Ahn, F. Schindler, M.N. Harakeh, J. Feng, J. Tscheuschner, S. Kim, Atsumi Saito, L. Zanetti, P. Koseoglou, V. Wagner, M. Parlog, B. M. Godoy, N. Orr, Takashi Nakamura, Yu-xin Liu, J. Mayer, A. Obertelli, Yuya Kubota, Hideaki Otsu, S. Storck, S. Masuoka, K. Boretzky, Kathrin Wimmer, H. Miki, T. Tomai, F. M. Marqués, V. Panin, P. Doornenbal, Stefanos Paschalis, L. Yang, Satoshi Takeuchi, M. A. Knösel, Igor Gašparić, T. Kobayashi, C. Lehr, H. Yang, C. Lenain, M. Miwa, Z. Halász, A. Revel, H. Sato, T. Fujino, D. M. Rossi, H. Baba, S. Park, I. Murray, L. Stuhl, H. Yamada, J. Gibelin, J. Tanaka, Naoki Fukuda, RIKEN Nishina Center for Accelerator-Based Science, German Research Foundation, Federal Ministry of Education and Research (Germany), 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), 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), Institut de Recherches sur les lois Fondamentales de l'Univers (IRFU), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay, Grand Accélérateur National d'Ions Lourds (GANIL), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), Normandie Université (NU)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3), 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 Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)

Subjects
Physics, Paper, History, 010308 nuclear & particles physics, tetraneutron, nuclear force, proton knock-out, radioactive beams, [PHYS.NEXP]Physics [physics]/Nuclear Experiment [nucl-ex], 01 natural sciences, Computer Science Applications, Education, ddc, Nuclear physics, 0103 physical sciences, Tetraneutron, Neutron, ddc:530, 010306 general physics
Abstract

7 pags., 3 figs. -- 27th International Nuclear Physics Conference (INPC2019), The tetraneutron has attracted the attention of nuclear physicists during the past decades, but there is still no unambiguous confirmation of its existence or nonexistence. A new experiment based on 8 He(p,2p)7H{t+4n} reaction, with direct detection of the four neutrons, has been carried out at RIBF, which can hopefully help to draw a definite conclusion on the tetraneutron system., We acknowledge the support of the RIBF accelerator staff and the BigRIPS team for providing the high-quality beam. Z. H. Yang acknowledges the financial support from the Foreign Postdoctoral Researcher program of RIKEN. T. Aumann acknowledges the support by DFG via SFB 1245. P. Koseoglou acknowledges the support from BMBF (NUSTAR.DA grant No.05P 15RDFN1).

Published
2020
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7. Study of multi-neutron systems with SAMURAI spectrometer

Author

K. Yoneda, Z. Elekes, Masaki Sasano, Heiko Scheit, Atsumi Saito, N. Inabe, I. Stefan, J. Tscheuschner, Mohsen Harakeh, Julien Gibelin, M. A. Knösel, K. Boretzky, Z. Ge, Takashi Nakamura, D. Kim, H. Sato, J. Kahlbow, Igor Gašparić, Y. Yasuda, Susumu Shimoura, T. Isobe, Juzo Zenihiro, M. Caamaño, Yosuke Kondo, S. Masuoka, H. Suzuki, A. Hirayama, S. W. Huang, C. A. Douma, B. M. Godoy, Z. Halász, H. Yamada, C. Lehr, M. Böhmer, Nobuyuki Chiga, A. Revel, N. L. Achouri, P. Koseoglou, Kathrin Wimmer, V. Wagner, N. A. Orr, M. Potlog, M. Miwa, B. Yang, A. Obertelli, T. Harada, H. T. Törnqvsit, S. Reichert, H. Miki, D. S. Ahn, T. Tomai, István Kuti, J. Mayer, J. Tanaka, S. Park, Yasuhiro Togano, M. Parlog, Naoki Fukuda, Yu-xin Liu, S. Chen, V. Panin, L. Zanetti, F. Schindler, S. Storck, T. Shimada, Tomohiro Uesaka, J. Feng, M. Matsumoto, Zaihong Yang, U. Forsberg, Roman Gernhäuser, I. Murray, F. Dufter, D. Symochko, L. Stuhl, J. M. Gheller, Hideaki Otsu, D. Beaumel, T. Kobayashi, H. Takeda, A. Gillibert, D. Cortina, P. Doornenbal, L. Yang, Nasser Kalantar-Nayestanaki, Satoshi Takeuchi, Thomas Aumann, Stefanos Paschalis, T. Fujino, D. M. Rossi, H. Baba, Yohei Shimizu, M. L. Cortés, F. M. Marqués, B. Fernández-Domínguez, Yuya Kubota, Yukie Maeda, S. K. Kim, P. J. Li, 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), 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), Institut de Recherches sur les lois Fondamentales de l'Univers (IRFU), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay, Grand Accélérateur National d'Ions Lourds (GANIL), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), Normandie Université (NU)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3), 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 Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)

Subjects
Physics, Firm conclusion, Spectrometer, FOS: Physical sciences, [PHYS.NEXP]Physics [physics]/Nuclear Experiment [nucl-ex], 01 natural sciences, 010305 fluids & plasmas, Nuclear physics, 0103 physical sciences, Tetraneutron, Neutron, Nuclear Experiment (nucl-ex), 010306 general physics, Nuclear Experiment
Abstract

The tetraneutron has been drawing the attention of the nuclear physics community for decades, but a firm conclusion on its existence and properties is still far from being reached despite many experimental and theoretical efforts. New measurements have recently been performed at RIBF with the SAMURAI spectrometer by applying complementary reaction probes, which will help to pin down the properties of this four-neutron system., Comment: 5 pages, 2 figures, conference proceedings of XXII International Conference on Few-Body Problems in Physics (FB22), Caen, France, July 2018

Published
2018
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8. Low-lying dipole response in the unstable Ni70 nucleus

Author

A. Giaz, P. Doornenbal, F. C. L. Crespi, Takashi Nakamura, Ryo Taniuchi, C. Caesar, Hua-Lei Wang, Noritsugu Nakatsuka, S. Ceruti, R. Avigo, F. Camera, Naoki Fukuda, Shoko Koyama, H. Baba, Hideaki Otsu, O. Wieland, David Steppenbeck, Atsumi Saito, H. Scheit, J. Tsubota, Satoshi Takeuchi, K. Yoneda, S. R. Banerjee, Masafumi Matsushita, Yoshiaki Shiga, T. Ozaki, B. Million, Toshiyuki Sumikama, Thomas Aumann, Susumu Shimoura, Yosuke Kondo, A. Bracco, G. Benzoni, Hiroyoshi Sakurai, T. Motobayashi, Kazuo Ieki, M. Shikata, V. Derya, J. Tscheuschner, T. Kubo, Masanori Nishimura, Yasuhiro Togano, K. Boretzky, F. Schindler, Kathrin Wimmer, Nagao Kobayashi, P. Schrock, and Si-Ge Chen

Subjects
Physics, Dipole, medicine.anatomical_structure, 010308 nuclear & particles physics, 0103 physical sciences, medicine, Atomic physics, 010306 general physics, 01 natural sciences, Nucleus, Lying
Published
2018

9. Magicity versus Superfluidity around ^{28}O viewed from the Study of ^{30}F.

Author

Kahlbow J, Aumann T, Sorlin O, Kondo Y, Nakamura T, Nowacki F, Revel A, Achouri NL, Al Falou H, Atar L, Baba H, Boretzky K, Caesar C, Calvet D, Chae H, Chiga N, Corsi A, Delaunay F, Delbart A, Deshayes Q, Dombrádi Z, Douma CA, Elekes Z, Gašparić I, Gheller JM, Gibelin J, Gillibert A, Harakeh MN, Hirayama A, Holl M, Horvat A, Horváth Á, Hwang JW, Isobe T, Kalantar-Nayestanaki N, Kawase S, Kim S, Kisamori K, Kobayashi T, Körper D, Koyama S, Kuti I, Lapoux V, Lindberg S, Marqués FM, Masuoka S, Mayer J, Miki K, Murakami T, Najafi M, Nakano K, Nakatsuka N, Nilsson T, Obertelli A, Orr NA, Otsu H, Ozaki T, Panin V, Paschalis S, Rossi DM, Saito AT, Saito T, Sasano M, Sato H, Satou Y, Scheit H, Schindler F, Schrock P, Shikata M, Shimada K, Shimizu Y, Simon H, Sohler D, Stuhl L, Takeuchi S, Tanaka M, Thoennessen M, Törnqvist H, Togano Y, Tomai T, Tscheuschner J, Tsubota J, Uesaka T, Wang H, Yang Z, Yasuda M, and Yoneda K

Abstract

The neutron-rich unbound fluorine isotope ^{30}F_{21} has been observed for the first time by measuring its neutron decay at the SAMURAI spectrometer (RIBF, RIKEN) in the quasifree proton knockout reaction of ^{31}Ne nuclei at 235  MeV/nucleon. The mass and thus one-neutron-separation energy of ^{30}F has been determined to be S_{n}=-472±58(stat)±33(sys)  keV from the measurement of its invariant-mass spectrum. The absence of a sharp drop in S_{n}(^{30}F) shows that the "magic" N=20 shell gap is not restored close to ^{28}O, which is in agreement with our shell-model calculations that predict a near degeneracy between the neutron d and fp orbitals, with the 1p_{3/2} and 1p_{1/2} orbitals becoming more bound than the 0f_{7/2} one. This degeneracy and reordering of orbitals has two potential consequences: ^{28}O behaves like a strongly superfluid nucleus with neutron pairs scattering across shells, and both ^{29,31}F appear to be good two-neutron halo-nucleus candidates.

Published
2024
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10. Publisher Correction: First observation of 28 O.

Author

Kondo Y, Achouri NL, Falou HA, Atar L, Aumann T, Baba H, Boretzky K, Caesar C, Calvet D, Chae H, Chiga N, Corsi A, Delaunay F, Delbart A, Deshayes Q, Dombrádi Z, Douma CA, Ekström A, Elekes Z, Forssén C, Gašparić I, Gheller JM, Gibelin J, Gillibert A, Hagen G, Harakeh MN, Hirayama A, Hoffman CR, Holl M, Horvat A, Horváth Á, Hwang JW, Isobe T, Jiang WG, Kahlbow J, Kalantar-Nayestanaki N, Kawase S, Kim S, Kisamori K, Kobayashi T, Körper D, Koyama S, Kuti I, Lapoux V, Lindberg S, Marqués FM, Masuoka S, Mayer J, Miki K, Murakami T, Najafi M, Nakamura T, Nakano K, Nakatsuka N, Nilsson T, Obertelli A, Ogata K, de Oliveira Santos F, Orr NA, Otsu H, Otsuka T, Ozaki T, Panin V, Papenbrock T, Paschalis S, Revel A, Rossi D, Saito AT, Saito TY, Sasano M, Sato H, Satou Y, Scheit H, Schindler F, Schrock P, Shikata M, Shimizu N, Shimizu Y, Simon H, Sohler D, Sorlin O, Stuhl L, Sun ZH, Takeuchi S, Tanaka M, Thoennessen M, Törnqvist H, Togano Y, Tomai T, Tscheuschner J, Tsubota J, Tsunoda N, Uesaka T, Utsuno Y, Vernon I, Wang H, Yang Z, Yasuda M, Yoneda K, and Yoshida S

Published
2023
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11. First observation of 28 O.

Author

Kondo Y, Achouri NL, Falou HA, Atar L, Aumann T, Baba H, Boretzky K, Caesar C, Calvet D, Chae H, Chiga N, Corsi A, Delaunay F, Delbart A, Deshayes Q, Dombrádi Z, Douma CA, Ekström A, Elekes Z, Forssén C, Gašparić I, Gheller JM, Gibelin J, Gillibert A, Hagen G, Harakeh MN, Hirayama A, Hoffman CR, Holl M, Horvat A, Horváth Á, Hwang JW, Isobe T, Jiang WG, Kahlbow J, Kalantar-Nayestanaki N, Kawase S, Kim S, Kisamori K, Kobayashi T, Körper D, Koyama S, Kuti I, Lapoux V, Lindberg S, Marqués FM, Masuoka S, Mayer J, Miki K, Murakami T, Najafi M, Nakamura T, Nakano K, Nakatsuka N, Nilsson T, Obertelli A, Ogata K, de Oliveira Santos F, Orr NA, Otsu H, Otsuka T, Ozaki T, Panin V, Papenbrock T, Paschalis S, Revel A, Rossi D, Saito AT, Saito TY, Sasano M, Sato H, Satou Y, Scheit H, Schindler F, Schrock P, Shikata M, Shimizu N, Shimizu Y, Simon H, Sohler D, Sorlin O, Stuhl L, Sun ZH, Takeuchi S, Tanaka M, Thoennessen M, Törnqvist H, Togano Y, Tomai T, Tscheuschner J, Tsubota J, Tsunoda N, Uesaka T, Utsuno Y, Vernon I, Wang H, Yang Z, Yasuda M, Yoneda K, and Yoshida S

Abstract

Subjecting a physical system to extreme conditions is one of the means often used to obtain a better understanding and deeper insight into its organization and structure. In the case of the atomic nucleus, one such approach is to investigate isotopes that have very different neutron-to-proton (N/Z) ratios than in stable nuclei. Light, neutron-rich isotopes exhibit the most asymmetric N/Z ratios and those lying beyond the limits of binding, which undergo spontaneous neutron emission and exist only as very short-lived resonances (about 10 -21  s), provide the most stringent tests of modern nuclear-structure theories. Here we report on the first observation of 28 O and 27 O through their decay into 24 O and four and three neutrons, respectively. The 28 O nucleus is of particular interest as, with the Z = 8 and N = 20 magic numbers 1,2 , it is expected in the standard shell-model picture of nuclear structure to be one of a relatively small number of so-called 'doubly magic' nuclei. Both 27 O and 28 O were found to exist as narrow, low-lying resonances and their decay energies are compared here to the results of sophisticated theoretical modelling, including a large-scale shell-model calculation and a newly developed statistical approach. In both cases, the underlying nuclear interactions were derived from effective field theories of quantum chromodynamics. Finally, it is shown that the cross-section for the production of 28 O from a 29 F beam is consistent with it not exhibiting a closed N = 20 shell structure., (© 2023. The Author(s), under exclusive licence to Springer Nature Limited.)

Published
2023
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12. Observation of a correlated free four-neutron system.

Author

Duer M, Aumann T, Gernhäuser R, Panin V, Paschalis S, Rossi DM, Achouri NL, Ahn D, Baba H, Bertulani CA, Böhmer M, Boretzky K, Caesar C, Chiga N, Corsi A, Cortina-Gil D, Douma CA, Dufter F, Elekes Z, Feng J, Fernández-Domínguez B, Forsberg U, Fukuda N, Gasparic I, Ge Z, Gheller JM, Gibelin J, Gillibert A, Hahn KI, Halász Z, Harakeh MN, Hirayama A, Holl M, Inabe N, Isobe T, Kahlbow J, Kalantar-Nayestanaki N, Kim D, Kim S, Kobayashi T, Kondo Y, Körper D, Koseoglou P, Kubota Y, Kuti I, Li PJ, Lehr C, Lindberg S, Liu Y, Marqués FM, Masuoka S, Matsumoto M, Mayer J, Miki K, Monteagudo B, Nakamura T, Nilsson T, Obertelli A, Orr NA, Otsu H, Park SY, Parlog M, Potlog PM, Reichert S, Revel A, Saito AT, Sasano M, Scheit H, Schindler F, Shimoura S, Simon H, Stuhl L, Suzuki H, Symochko D, Takeda H, Tanaka J, Togano Y, Tomai T, Törnqvist HT, Tscheuschner J, Uesaka T, Wagner V, Yamada H, Yang B, Yang L, Yang ZH, Yasuda M, Yoneda K, Zanetti L, Zenihiro J, and Zhukov MV

Abstract

A long-standing question in nuclear physics is whether chargeless nuclear systems can exist. To our knowledge, only neutron stars represent near-pure neutron systems, where neutrons are squeezed together by the gravitational force to very high densities. The experimental search for isolated multi-neutron systems has been an ongoing quest for several decades 1 , with a particular focus on the four-neutron system called the tetraneutron, resulting in only a few indications of its existence so far 2-4 , leaving the tetraneutron an elusive nuclear system for six decades. Here we report on the observation of a resonance-like structure near threshold in the four-neutron system that is consistent with a quasi-bound tetraneutron state existing for a very short time. The measured energy and width of this state provide a key benchmark for our understanding of the nuclear force. The use of an experimental approach based on a knockout reaction at large momentum transfer with a radioactive high-energy 8 He beam was key., (© 2022. The Author(s).)

Published
2022
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13. Pairing Forces Govern Population of Doubly Magic ^{54}Ca from Direct Reactions.

Author

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

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
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14. Extending the Southern Shore of the Island of Inversion to ^{28}F.

Author

Revel A, Sorlin O, Marqués FM, Kondo Y, Kahlbow J, Nakamura T, Orr NA, Nowacki F, Tostevin JA, Yuan CX, Achouri NL, Al Falou H, Atar L, Aumann T, Baba H, Boretzky K, Caesar C, Calvet D, Chae H, Chiga N, Corsi A, Crawford HL, Delaunay F, Delbart A, Deshayes Q, Dombrádi Z, Douma CA, Elekes Z, Fallon P, Gašparić I, Gheller JM, Gibelin J, Gillibert A, Harakeh MN, He W, Hirayama A, Hoffman CR, Holl M, Horvat A, Horváth Á, Hwang JW, Isobe T, Kalantar-Nayestanaki N, Kawase S, Kim S, Kisamori K, Kobayashi T, Körper D, Koyama S, Kuti I, Lapoux V, Lindberg S, Masuoka S, Mayer J, Miki K, Murakami T, Najafi M, Nakano K, Nakatsuka N, Nilsson T, Obertelli A, de Oliveira Santos F, Otsu H, Ozaki T, Panin V, Paschalis S, Rossi D, Saito AT, Saito T, Sasano M, Sato H, Satou Y, Scheit H, Schindler F, Schrock P, Shikata M, Shimizu Y, Simon H, Sohler D, Stuhl L, Takeuchi S, Tanaka M, Thoennessen M, Törnqvist H, Togano Y, Tomai T, Tscheuschner J, Tsubota J, Uesaka T, Yang Z, Yasuda M, and Yoneda K

Abstract

Detailed spectroscopy of the neutron-unbound nucleus ^{28}F has been performed for the first time following proton/neutron removal from ^{29}Ne/^{29}F beams at energies around 230  MeV/nucleon. The invariant-mass spectra were reconstructed for both the ^{27}F^{(*)}+n and ^{26}F^{(*)}+2n coincidences and revealed a series of well-defined resonances. A near-threshold state was observed in both reactions and is identified as the ^{28}F ground state, with S_{n}(^{28}F)=-199(6)  keV, while analysis of the 2n decay channel allowed a considerably improved S_{n}(^{27}F)=1620(60)  keV to be deduced. Comparison with shell-model predictions and eikonal-model reaction calculations have allowed spin-parity assignments to be proposed for some of the lower-lying levels of ^{28}F. Importantly, in the case of the ground state, the reconstructed ^{27}F+n momentum distribution following neutron removal from ^{29}F indicates that it arises mainly from the 1p_{3/2} neutron intruder configuration. This demonstrates that the island of inversion around N=20 includes ^{28}F, and most probably ^{29}F, and suggests that ^{28}O is not doubly magic.

Published
2020
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15. Fragmentation of Single-Particle Strength around the Doubly Magic Nucleus  ^{132}Sn and the Position of the 0f_{5/2} Proton-Hole State in ^{131}In.

Author

Vaquero V, Jungclaus A, Aumann T, Tscheuschner J, Litvinova EV, Tostevin JA, Baba H, Ahn DS, Avigo R, Boretzky K, Bracco A, Caesar C, Camera F, Chen S, Derya V, Doornenbal P, Endres J, Fukuda N, Garg U, Giaz A, Harakeh MN, Heil M, Horvat A, Ieki K, Imai N, Inabe N, Kalantar-Nayestanaki N, Kobayashi N, Kondo Y, Koyama S, Kubo T, Martel I, Matsushita M, Million B, Motobayashi T, Nakamura T, Nakatsuka N, Nishimura M, Nishimura S, Ota S, Otsu H, Ozaki T, Petri M, Reifarth R, Rodríguez-Sánchez JL, Rossi D, Saito AT, Sakurai H, Savran D, Scheit H, Schindler F, Schrock P, Semmler D, Shiga Y, Shikata M, Shimizu Y, Simon H, Steppenbeck D, Suzuki H, Sumikama T, Symochko D, Syndikus I, Takeda H, Takeuchi S, Taniuchi R, Togano Y, Tsubota J, Wang H, Wieland O, Yoneda K, Zenihiro J, and Zilges A

Abstract

Spectroscopic factors of neutron-hole and proton-hole states in ^{131}Sn and ^{131}In, respectively, were measured using one-nucleon removal reactions from doubly magic ^{132}Sn at relativistic energies. For ^{131}In, 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 single-hole strength in ^{131}Sn and ^{131}In. The experimental results are compared to theoretical calculations based on the relativistic particle-vibration coupling model and to experimental information for single-hole states in the stable doubly magic nucleus ^{208}Pb.

Published
2020
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