Bound state properties from the Functional Renormalisation Group

TL;DR

This paper presents a method using the functional renormalisation group to compute bound state properties like mass and decay width, validated within a two-flavour quark-meson model and compared with first-principle QCD results.

Contribution

It introduces a dynamical hadronization technique for resonant channels within the FRG framework and applies it to a low-energy QCD model to extract bound state properties.

Findings

Quantitative comparison of correlation functions with QCD results

First estimates of pole masses and decay widths

Assessment of low-energy model validity range

Abstract

We discuss an approach for accessing bound state properties, like mass and decay width, of a theory within the functional renormalisation group approach. An important cornerstone is the dynamical hadronization technique for resonant interaction channels. The general framework is exemplified and put to work within the two-flavour quark-meson model. This model provides a low-energy description of the dynamics of two-flavour QCD with quark and hadronic degrees of freedom. We compare explicitly the respective results for correlation functions and observables with first principle QCD results in a quantitative manner. This allows us to estimate the validity range of low energy effective models. We also present first results for pole masses and decay widths. Next steps involving real-time formulations of the functional renormalisation group are discussed.