Dineutron in the $2^+_1$ state of $^6$He

TL;DR

This study analyzes the dineutron configuration in the $2^+_1$ state of $^6$He using complex scaling to identify a shoulder peak in the cross section, indicating dineutron presence.

Contribution

It introduces a method to distinguish resonant contributions and identifies a signature peak associated with the dineutron in the $2^+_1$ state of $^6$He.

Findings

Shoulder peak appears in the cross section for the resonant state.

The $S=0$ component peaks near the shoulder, indicating dineutron configuration.

The shoulder peak suggests the existence of a dineutron in the $2^+_1$ state.

Abstract

We investigate the dineutron in the $2^+_1$ state of $^6$He via analysis of its decay mode by using the complex scaling method. In this letter, we propose the cross section for the resonant state to distinguish the resonant contributions from the nonresonant ones. As the results, it is found that the shoulder peak appears in the cross section for the resonant state as a function of $\varepsilon_{n\text{-}n}$. Furthermore, we show that the $S$ = 0 component of the cross section, where $S$ is the total spin of the valence two neutrons, has a peak around the shoulder peak, which comes from the dineutron configuration in the $2^+_1$ state. Thus we conclude that the shoulder peak is expected to indicate the existence of the dineutron in the $2^+_1$ state.