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

Abstract

Partial cross-sections of the [Formula: see text] and [Formula: see text] collisions in the quantum state [Formula: see text] near the [Formula: see text]-threshold, taken from an available [Formula: see text]-matrix analysis, 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 [Formula: see text]-matrix poles) at complex energies. The correct analytic structure makes it possible to calculate (analytically continue) 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. As a result of such an analytic continuation, it was found that the previously established [Formula: see text]-resonance (at [Formula: see text]) and its shadow pole (at [Formula: see text]) both are split in overlapping pairs. Apart from studying the properties of a specific nuclear state, it is also proved for a general multi-channel problem that the Coulomb forces change the topology of the Riemann surface as well as destroy the so-called mirror symmetry of the [Formula: see text]-matrix.