Jost-matrix analysis of the resonance 5He*(3/2+) near the dt-threshold

TL;DR

This paper uses a semi-analytic Jost matrix approach to analyze resonance states near the dt-threshold in n-alpha and dt collisions, identifying multiple resonances and S-matrix poles with complex analytic structure.

Contribution

It introduces a proper analytic Jost matrix framework for multi-channel scattering, enabling precise resonance and pole identification near the dt-threshold.

Findings

Identified three 3/2+ resonances within 100 keV above the dt-threshold.

Located several shadow S-matrix poles on different Riemann sheets.

Demonstrated the importance of correct analytic structure in resonance analysis.

Abstract

Experimental data on the n-alpha and dt collisions in the quantum state J^pi=3/2+ near the dt-threshold are fitted using the semi-analytic multi-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. Within a distance of 100,keV above the dt-threshold, three 3/2+ resonances are found on the non-physical sheet of the Riemann surface. Several S-matrix (shadow) poles on the other sheets of this surface are located as well.