The covalent bond in Particle Spectroscopy

TL;DR

This paper proposes a novel analogy between covalent bonds in molecular physics and the mixing of quark-antiquark and meson-meson states in meson and baryon resonances, explaining their physical behavior and threshold effects.

Contribution

It introduces a new conceptual framework using covalent bond analogy to understand resonance mixing and threshold phenomena in particle spectroscopy.

Findings

Mixing causes eigenstate energy shifts and width changes.

Cusps at thresholds significantly influence experimental data.

The analogy clarifies physical interpretation of resonance phenomena.

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.