Quasifree Neutron Knockout Reaction Reveals a Small <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>s</mml:mi></mml:math>-Orbital Component in the Borromean Nucleus <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mmultiscripts><mml:mrow><mml:mi mathvariant="normal">B</mml:mi></mml:mrow><mml:mprescripts/><mml:none/><mml:mrow><mml:mn>17</mml:mn></mml:mrow></mml:mmultiscripts></mml:mrow></mml:math>
Z. Yang, Y. Kubota, A. Corsi, K. Yoshida, Xiang-Xiang Sun, J. G. Li, Masashi Kimura, N. Michel, Kazuyuki Ogata, Cenxi Yuan, Qiong Yuan, G. Authelet, H. Baba, C. Caesar, D. Calvet, A. Delbart, M. Dozono, Jie Feng, F. Flavigny, J.-M. Gheller, J. Gibelin, A. Giganon, A. Gillibert, K. Hasegawa, T. Isobe, Y. Kanaya, Satoshi Kawakami, D. Kim, Yasushi Kiyokawa, Masaaki 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. Saito, S. Sakaguchi, M. Sako, C. Santamaria, M. Sasano, Y. Satou, M. Shikata, Y. Shimizu, Y. Shindo, L. Stuhl, T. Sumikama, Y. Sun, M. Tabata, Y. Togano, J. Tsubota, F. R. Xu, Jumpei Yasuda, K. Yoneda, J. Zenihiro, Shan-Gui Zhou, W. Zuo, Т. Уесака
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.