Quasi-free neutron knockout reaction reveals a small s-orbital component in the Borromean nucleus 17B
发表刊物： Physical Review Letters
摘要： A kinematically complete quasi-free (p,pn) experiment in inverse kinematics was performed to study the structure of the Borromean nucleus 17B, which had long been considered to have neutron halo. By analyzing the momentum distributions and exclusive cross sections, we obtained the spectroscopic factors for 1s1/2 and 0d5/2 orbitals, and a surprisingly small percentage of 9(2)% was determined for 1s1/2. Our finding of such a small 1s1/2 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 17B. 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 neutron halo.