# Solution of the eta-4He problem with quasi-particle formalism

## TL;DR

This paper solves the eta-4He scattering problem using a quasi-particle formalism to simplify complex five-body equations, providing numerical results for scattering length.

## Contribution

It introduces a quasi-particle approach to reduce five-body eta-4N equations to an effective two-body form, enabling practical calculations.

## Key findings

- Calculated eta-4He scattering length
- Demonstrated effectiveness of quasi-particle formalism
- Provided numerical benchmarks for eta-4N interactions

## Abstract

The Alt-Grassberger-Sandhas equations for the five-body eta-4N problem are solved for the case of the driving eta N and NN potentials limited to s-waves. The quasi-particle (Schmidt) method is employed to convert the equations into the effective two-body form. Numerical results are presented for the eta-4He scattering length.