Can Ab Initio Theory Explain the Phenomenon of Parity Inversion in ${}^{11}$Be?

TL;DR

This study uses ab initio methods with chiral nuclear forces to explain the parity inversion in ${}^{11}$Be, emphasizing the importance of continuum effects and specific interactions for accurate predictions.

Contribution

It demonstrates that only certain chiral three-nucleon forces can reproduce the parity inversion and related phenomena in ${}^{11}$Be from first principles.

Findings

Reproduces the parity inversion with specific chiral interactions.

Predicts a dip in photodisintegration cross-section near the resonance.

Identifies low-lying resonances not yet measured experimentally.

Abstract

The weakly bound exotic ${}^{11}$Be nucleus, famous for its ground-state parity inversion and distinct n+ ${}^{10}$Be halo structure, is investigated from first principles using chiral two- and three-nucleon forces. An explicit treatment of continuum effects is found to be indispensable. We study the sensitivity of the ${}^{11}$Be spectrum to the details of the three-nucleon force and demonstrate that only certain chiral interactions are capable of reproducing the parity inversion. With such interactions, the extremely large E1 transition between the bound states is reproduced. We compare our photodisintegration calculations to conflicting experimental data and predict a distinct dip around the $3/2^-_1$ resonance energy. Finally, we predict low-lying $3/2^+$ and $9/2^+$ resonances that are not or not sufficiently measured in experiments.