Hadronic resonances enhanced by thresholds

TL;DR

This paper investigates how the proximity of multiple thresholds can enhance hadronic resonance binding, specifically in meson-baryon systems, affecting the pattern of states across different flavor sectors.

Contribution

It demonstrates that threshold effects can significantly alter the binding and spectrum of hadronic states, challenging naive extrapolations in heavy flavor sectors.

Findings

Threshold proximity enhances resonance binding.

Flavor sector changes affect resonance patterns.

Coupled-channel effects influence state formation.

Abstract

We present a neat example of a meson--baryon system where the vicinity of two different thresholds enhances the binding of a hadronic resonance, a pentaquark. As a consequence the pattern of states may change when moving among different flavor sectors, what poses a warning on naive extrapolations to heavy flavor sectors based on systematic expansions. For this purpose we simultaneously analyze the $N\bar D$ and $NB$ two-hadron systems looking for possible bound states or resonances. When a resonance is controlled by a coupled-channel effect, going to a different flavor sector may enhance or diminish the binding. This effect may, for example, generate significant differences between the charmonium and bottomonium spectra above open-flavor thresholds or pentaquark states in the open-charm and open-bottom sectors.