Resonance-state properties from a phase shift analysis with the $S$-matrix pole method and the effective-range method

TL;DR

This paper introduces a new method combining the $S$-matrix pole and effective-range approaches to analyze resonance states and calculate asymptotic normalization coefficients (ANCs) for specific nuclear resonances, aiding nuclear astrophysics research.

Contribution

The paper develops a novel analytical relationship between ANC and the Coulomb-nuclear scattering amplitude, and compares resonance parameters obtained via the $S$-matrix pole and effective-range methods.

Findings

Derived a new relationship between ANC and scattering amplitude.

Calculated resonance parameters for $^5$He, $^5$Li, and $^{16}$O.

Found ANC values relevant for astrophysical reaction rates.

Abstract

Asymptotic normalization coefficients (ANCs) are fundamental nuclear constants playing an important role in nuclear physics and astrophysics. We derive a new useful relationship between ANC of the Gamow radial wave function and the renormalized (due to the Coulomb interaction) Coulomb-nuclear partial scattering amplitude. We use an analytical approximation in the form of a series for the nonresonant part of the phase shift which can be analytically continued to the point of an isolated resonance pole in the complex plane of the momentum. Earlier, this method which we call the $S$-matrix pole method was used by us to find the resonance pole energy. We find the corresponding fitting parameters for the $^5\rm{He},\,^5\rm{Li}$, and $^{16}\rm{O}$ concrete resonance states. Additionally, based on the theory of the effective range, we calculate the parameters of the $p_{3/2}$ and $p_{1/2}$ resonance states of the nuclei $^5\rm{He}$ and $^5\rm{Li}$ and compare them with the results obtained by the $S$-matrix pole method. ANC values are found which can be used to calculate the reaction rate through the $^{16}\rm{O}$ resonances which lie slightly above the threshold for the $\alpha^{12}\rm{C}$ channel.