Infinite volume, three-body scattering formalisms in the presence of bound states

TL;DR

This paper compares two relativistic three-body scattering formalisms, EFT-based and unitarity-based, for systems with bound states, providing numerical solutions and discussing their relevance to lattice QCD and multi-hadron phenomenology.

Contribution

It offers a detailed comparison and extension of EFT-based and unitarity-based three-body scattering formalisms, including numerical solutions and methods to handle open channels and singularities.

Findings

Numerical solutions for multi-hadron scattering amplitudes in different kinematic regions.

Extension of the unitarity-based framework to include all relevant open channels.

Discussion of nonphysical singularities and their elimination in the scattering formalism.

Abstract

Strong interactions produce a rich spectrum of resonances that decay into three or more hadrons. Understanding their phenomenology requires a theoretical framework to extract parameters fromexperimental data and Lattice QCD simulations of hadron scattering. Two classes of relativistic three-body approaches are currently being pursued: the EFT-based and unitarity-based one. We consider a model of relativistic three-body scattering with an S-wave bound state in the two-body sub-channel using both formalisms. We present and discuss numerical solutions for the multi-hadron scattering amplitudes in different kinematical regions, obtained from integral equationsof the EFT-based approach. The connection of our work to the ongoing program of computingthe three-body spectrum from the lattice is highlighted. Finally, we show how to generalizethe unitarity-based framework to include all relevant open channels, discuss the nonphysicalsingularities near the physical region, and show how to eliminate them in a simple case.