Structure of near-threshold resonances with new interpretation scheme of complex compositeness

TL;DR

This paper introduces a new interpretation scheme for complex compositeness to better understand the internal structure of near-threshold resonances, revealing they are dominated by non-molecular components.

Contribution

The paper develops a novel interpretation scheme for complex compositeness that overcomes previous ambiguities in analyzing unstable resonances' internal structures.

Findings

Near-threshold resonances are dominated by non-molecular components.

The new scheme clarifies the internal structure of resonances above the threshold.

Resonances differ sharply from bound states in their internal composition.

Abstract

The nature of near-threshold resonances is quantitatively studied with a new interpretation scheme using the complex compositeness. A difficulty was known in the understanding of the internal structure of unstable resonances because their complex compositeness is not an interpretable measure. To overcome this problem, we develop a new interpretation scheme respecting the ambiguous aspects of the identification of the internal structure of resonances. We then apply the interpretation scheme to the near-threshold resonances slightly above the threshold, described by the effective range expansion. With the new interpretation scheme, we show that near-threshold resonances are dominated by the non-molecular component. Namely, even in the near-threshold region, the nature of resonances is sharply contrasted with bound states whose internal structure is usually molecular dominant.