Quasifree neutron knockout reaction reveals a small -Orbital component in the Borromean nucleus B

Yang, Z. H.*; Kubota, Yuki*; Corsi, A.*; Yoshida, Kazuki   ; Sun, X.-X.*; Li, J. G.*; Kimura, Masaaki*; Michel, N.*; Ogata, Kazuyuki*; Yuan, C. X.*; Yuan, Q.*; Authelet, G.*; Baba, Hidetada*; Caesar, C.*; Calvet, D.*; Delbart, A.*; Dozono, Masanori*; Feng, J.*; Flavigny, F.*; Gheller, J.-M.*; Gibelin, J.*; Giganon, A.*; Gillibert, A.*; Hasegawa, K.*; Isobe, Tadaaki*; Kanaya, Yoshihiro*; Kawakami, Shunsuke*; Kim, D.*; Kiyokawa, Y.*; Kobayashi, Motoki*; Kobayashi, N.*; Kobayashi, T.*; Kondo, Yosuke*; Korkulu, Z.*; Koyama, Shumpei*; Lapoux, V.*; Maeda, Yukie*; Marqus, F. M.*; Motobayashi, Toru*; Miyazaki, T.*; Nakamura, Takashi*; Nakatsuka, Noritsugu*; Nishio, Y.*; Obertelli, A.*; Okura, Ayaka*; Orr, N. A.*; Ota, Shinsuke*; Otsu, Hideaki*; Ozaki, Tomoyuki*; Panin, V.*; Paschalis, S.*; Pollacco, E. C.*; Reichert, S.*; Rouss, J.-Y.*; Saito, Atsumi*; Sakaguchi, Satoshi*; Sako, M.*; Santamaria, C.*; Sasano, Masaki*; Sato, H.*; Shikata, Mizuki*; Shimizu, Y.*; Shindo, Yusuke*; Stuhl, L.*; Sumikama, Toshiyuki*; Sun, Y. L.*; Tabata, M.*; Togano, Yasuhiro*; Tsubota, Junichi*; Xu, F. R.*; Yasuda, Jumpei*; Yoneda, Kenichiro*; Zenihiro, Juzo*; Zhou, S.-G.*; Zuo, W.*; Uesaka, Tomohiro*

A quasifree (,) experiment was performed to study the structure of the Borromean nucleus 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 and orbitals, and a surprisingly small percentage of 9(2)% was determined for . Our finding of such a small 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 B. The present work gives the smallest - or -orbital component among known nuclei exhibiting halo features and implies that the dominant occupation of or orbitals is not a prerequisite for the occurrence of a neutron halo.