Two-Neutron Halo is Unveiled in ^{29}F

S. Bagchi, R. Kanungo, Y. K. Tanaka, H. Geissel, P. Doornenbal, W. Horiuchi, G. Hagen, T. Suzuki, N. Tsunoda, D. S. Ahn, H. Baba, K. Behr, F. Browne, S. Chen, M. L. Cortés, A. Estradé, N. Fukuda, M. Holl, K. Itahashi, N. IwasaG. R. Jansen, W. G. Jiang, S. Kaur, A. O. Macchiavelli, S. Y. Matsumoto, S. Momiyama, I. Murray, T. Nakamura, S. J. Novario, H. J. Ong, T. Otsuka, T. Papenbrock, S. Paschalis, A. Prochazka, C. Scheidenberger, P. Schrock, Y. Shimizu, D. Steppenbeck, H. Sakurai, D. Suzuki, H. Suzuki, M. Takechi, H. Takeda, S. Takeuchi, R. Taniuchi, K. Wimmer, K. Yoshida

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We report the measurement of reaction cross sections (σ_{R}^{ex}) of ^{27,29}F with a carbon target at RIKEN. The unexpectedly large σ_{R}^{ex} and derived matter radius identify ^{29}F as the heaviest two-neutron Borromean halo to date. The halo is attributed to neutrons occupying the 2p_{3/2} orbital, thereby vanishing the shell closure associated with the neutron number N=20. The results are explained by state-of-the-art shell model calculations. Coupled-cluster computations based on effective field theories of the strong nuclear force describe the matter radius of ^{27}F but are challenged for ^{29}F.

Original languageEnglish
Article number222504
Number of pages7
JournalPhysical Review Letters
Issue number22
Publication statusPublished - 5 Jun 2020

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