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 Iwasa; G 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

doi:10.1103/PhysRevLett.124.222504

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

Phys Rev Lett. 2020 Jun 5;124(22):222504. doi: 10.1103/PhysRevLett.124.222504.

Authors

S Bagchi^{1

2

3}, R Kanungo^{1

4}, Y K Tanaka^{1

2

3}, H Geissel^{2

3}, P Doornenbal⁵, W Horiuchi⁶, G Hagen^{7

8}, T Suzuki⁹, N Tsunoda¹⁰, D S Ahn⁵, H Baba⁵, K Behr², F Browne⁵, S Chen⁵, M L Cortés⁵, A Estradé¹¹, N Fukuda⁵, M Holl^{1

4}, K Itahashi⁵, N Iwasa¹², G R Jansen^{7

13}, W G Jiang^{7

8}, S Kaur^{1

14}, A O Macchiavelli¹⁵, S Y Matsumoto¹⁶, S Momiyama¹⁷, I Murray^{5

18}, T Nakamura¹⁹, S J Novario^{7

8}, H J Ong²⁰, T Otsuka^{5

17}, T Papenbrock^{7

8}, S Paschalis²¹, A Prochazka², C Scheidenberger^{2

3}, P Schrock²², Y Shimizu⁵, D Steppenbeck^{5

22}, H Sakurai^{5

17}, D Suzuki⁵, H Suzuki⁵, M Takechi²³, H Takeda⁵, S Takeuchi¹⁹, R Taniuchi^{17

21}, K Wimmer¹⁷, K Yoshida⁵

Affiliations

¹ Astronomy and Physics Department, Saint Mary's University, Halifax, Nova Scotia B3H 3C3, Canada.
² GSI Helmholtzzentrum für Schwerionenforschung GmbH, D-64291 Darmstadt, Germany.
³ Justus-Liebig University, 35392 Giessen, Germany.
⁴ TRIUMF, Vancouver, British Columbia V6T 2A3, Canada.
⁵ RIKEN Nishina Center, Wako, Saitama 351-0198, Japan.
⁶ Department of Physics, Hokkaido University, Sapporo 060-0810, Japan.
⁷ Physics Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA.
⁸ Department of Physics and Astronomy, University of Tennessee, Knoxville, Tennessee 37996, USA.
⁹ Department of Physics, Nihon University, Setagaya-ku, Tokyo 156-8550, Japan.
¹⁰ Center for Nuclear Study, University of Tokyo, Bunkyo-ku, Tokyo 113-0033, Japan.
¹¹ Department of Physics, Central Michigan University, Mount Pleasant, Michigan 48859, USA.
¹² Department of Physics, Tohoku University, Miyagi 980-8577, Japan.
¹³ National Center for Computational Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA.
¹⁴ Department of Physics and Atmospheric Science, Dalhousie University, Halifax, Nova Scotia B3H 4R2, Canada.
¹⁵ Nuclear Science Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA.
¹⁶ Department of Physics, Kyoto University, Kyoto 606-8502, Japan.
¹⁷ Department of Physics, University of Tokyo, Bunkyo-ku, Tokyo 113-0033, Japan.
¹⁸ Institut de Physique Nucleaire, IN2P3, CNRS, Université Paris-Sud, Université Paris-Saclay, 91406 Orsay Cedex, France.
¹⁹ Department of Physics, Tokyo Institute of Technology, 2-12-1 O-Okayama, Meguro, Tokyo 152-8551, Japan.
²⁰ RCNP, Osaka University, Mihogaoka, Ibaraki, Osaka 567 0047, Japan.
²¹ Department of Physics, University of York, Heslington, York YO10 5DD, United Kingdom.
²² Center for Nuclear Study, University of Tokyo, RIKEN Campus, Wako, Saitama 351-0198, Japan.
²³ Graduate School of Science and Technology, Niigata University, Niigata 950-2102, Japan.

PMID: 32567915
DOI: 10.1103/PhysRevLett.124.222504

Abstract

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.