Annihilating States in Close-Coupling Method for Collisions between Hadronic and Ordinary Atoms

TL;DR

This paper extends the close-coupling method to include annihilating states in hadronic-atom collisions, accounting for non-hermitian effects and providing a numerical scheme for such complex interactions.

Contribution

It introduces a generalized close-coupling approach that incorporates annihilating states and non-unitary S-matrix calculations for hadronic atom collisions.

Findings

The method correctly models wave function damping in annihilating channels.

The non-hermitian Hamiltonian leads to a non-unitary S-matrix.

A numerical scheme for solving the generalized equations is proposed.

Abstract

Traditional close-coupling methods suppose an expansion of the total wave function in terms of inner stationary states of colliding subsystems. In the case of hadronic atoms, a similar expansion has to involve, \emph{inter alia}, low angular momentum states (ns, np) with large annihilation or nuclear absorbtion widths. The life times of these states are small as compared with the collision time and mean time between subsequent collisions, therefore the close-coupling approach has to be modified for the similar problems. In this paper we propose a generalization of the close-coupling method with annihilating states included in the basis. The correct asymptotic behaviour of the wave function in the annihilating channels suppose that the annihilating states can not be presented in the incoming channels whereas the corresponding components of the wave function of relative motion in outgoing channels have to damp out at large distances. The S-matrix of the transitions in the subspace of all other (non-annihilating) states is not unitary, because the hamiltonian of the problem is non-hermitian. The unitary defect gives the cross section of induced annihilation. The scheme of the numerical solving of the generalized close-coupling equations is proposed. It includes the calculations of two types of solution, from the origin to an intermediate sewing point R=a and from a large R to the point a.