Pairing Forces Govern Population of Doubly Magic Ca 54 from Direct Reactions

F. Browne*, S. Chen, P. Doornenbal, A. Obertelli, K. Ogata, 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. IsobeT. 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, M. Holl, J. Kahlbow, D. Kim, D. Körper, T. Koiwai, Y. Kondo, P. Koseoglou, J. Lee, 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. Törnqvist, J. Tscheuschner, V. Vaquero, V. Wagner, S. Wang, V. Werner, X. Xu, H. Yamada, D. Yan, Z. Yang, M. Yasuda, L. Zanetti

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


Direct proton-knockout reactions of Sc55 at ∼220 MeV/nucleon were studied at the RIKEN Radioactive Isotope Beam Factory. Populated states of Ca54 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 Sc55 ground state with states in Ca54. Despite the calculations showing a significant amplitude of excited neutron configurations in the ground-state of Sc55, valence proton removals populated predominantly the ground state of Ca54. 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.

Original languageEnglish
Article number252501
JournalPhysical Review Letters
Issue number25
StatePublished - 25 Jun 2021
Externally publishedYes


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