Abstract
A kinematically complete quasifree experiment in inverse kinematics was performed to study the structure of the Borromean nucleus , 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 . 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.
- Received 6 October 2020
- Revised 7 December 2020
- Accepted 27 January 2021
DOI:https://doi.org/10.1103/PhysRevLett.126.082501
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