Roles of tensor and pairing correlations on halo formation inLi11

Abstract

We studied the roles of the tensor and pairing correlations on the halo formation in $^{11}\mathrm{Li}$ with an extended $^{9}\mathrm{Li}+n+n$ model. We first solved the ground state of $^{9}\mathrm{Li}$ in the shell-model basis by taking 2p-2h states using the Gaussian functions with variational size parameters to take into account the tensor correlation fully. In $^{11}\mathrm{Li}$, the tensor and pairing correlations in $^{9}\mathrm{Li}$ are Pauli blocked by additional two neutrons, which work coherently to make the configurations containing the $0{p}_{1/2}$-state pushed up and close to those containing the $1{s}_{1/2}$-state. Hence, the pairing interaction works efficiently to mix the two configurations by equal amount and develop the halo structure in $^{11}\mathrm{Li}$. For $^{10}\mathrm{Li}$, the inversion phenomenon of $s$- and $p$-states is reproduced in the same framework. Our model furthermore explains the recently observed Coulomb breakup strength and charge radius for $^{11}\mathrm{Li}$.