# Resonance states 0+ of the Boron isotope B8 from the Jost-matrix analysis of experimental data

## TL;DR

This paper analyzes experimental scattering data for Beryllium-8 to identify resonance states using a sophisticated Jost matrix approach, revealing two overlapping 0+ resonances at specific energies.

## Contribution

It introduces a semi-analytic two-channel Jost matrix method with proper analytic structure to accurately identify resonance states from experimental data.

## Key findings

- Identified two overlapping 0+ resonances at ~1.79 MeV and ~1.96 MeV.
- Developed a method to calculate the Jost matrix on complex Riemann sheets.
- Enhanced understanding of B8 resonance structure.

## Abstract

The available R-matrix parametrization of experimental data on the excitation functions for the elastic and inelastic p-Be7 scattering at the collision energies up to 3.4 MeV is used to generate the corresponding partial-wave cross sections in the states with J^pi=0+. Thus obtained data are considered as experimental partial cross sections and are fitted using the semi-analytic two-channel Jost matrix with proper analytic structure and some adjustable parameters. Then the spectral points are sought as zeros of the Jost matrix determinant (which correspond to the S-matrix poles) at complex energies. The correct analytic structure makes it possible to calculate the fitted Jost matrix on any sheet of the Riemann surface whose topology involves not only the square-root but also the logarithmic branching caused by the Coulomb interaction. In this way, two overlapping 0+ resonances at the excitation energies ~1.79 MeV and ~1.96 MeV have been found.