Remarks on meson loop effects on quark models

TL;DR

This paper studies how meson loops influence quark state spectra, revealing that strong coupling can lead to decoupling rather than broadening, with some resonances showing collective behavior due to multiple pole contributions.

Contribution

It demonstrates that meson loop effects can cause quark states to decouple at strong coupling, challenging traditional expectations of broadening, and highlights the collective behavior of certain resonances.

Findings

Quark states do not become very broad with increased coupling.

Some resonances exhibit collective behavior with wide pole trajectories.

Results suggest these effects may be general beyond simplified models.

Abstract

We investigate the effect of meson loops on the spectrum of quark states. We demonstrate that in general quark states do not tend to get very broad if their coupling to the continuum increases, but instead they decouple from the latter in the large coupling limit. We ascribe this effect to the essentially nonperturbative unitarization procedure involved. In the meantime, some quark resonances behave very differently and demonstrate collectivity in the sense that their pole trajectories span a wide, as compared to the level spacing, region therefore acquiring contributions from multiple bare poles rather than from the closest neighbors. While the actual calculations are done within particular, very simplified models, it is argued that the findings might well be general.