A helpful analogy between the covalent bond and Particle Spectroscopy

TL;DR

This paper draws an analogy between covalent bonds in molecular physics and the mixing of quark-antiquark and meson-meson states in meson and baryon resonances, providing a new visualization of their physical behavior.

Contribution

It introduces a novel analogy linking covalent bonds to meson and baryon resonance mixing, offering a new perspective on their structure and decay patterns.

Findings

Light mesons follow nearly linear Regge trajectories.

Cusps at decay thresholds significantly influence data patterns.

The pattern of light mesons aligns with q-qbar components rather than purely dynamically generated states.

Abstract

It is proposed that meson resonances are linear combinations of q-qbar and meson-meson (MM); baryon resonances are combinations of qqq and meson-baryon (MB). Mixing between these combinations arises via decays of confined states to meson-meson or meson-baryon. There is a precise analogy with the covalent bond in molecular physics; it helps to visualise what is happening physically. One eigenstate is lowered by the mixing; the other moves up and normally increases in width. Cusps arise at thresholds. At sharp thresholds due to S-wave 2-particle decays, these cusps play a conspicuous role in many sets of data. The overall pattern of light mesons is consistent with nearly linear Regge trajectories, hence q-qbar components. There is no obvious reason why this pattern should arise from dynamically generated states without q-qbar content.