Resonances Do Not Equilibrate

TL;DR

This paper investigates the non-equilibrium behavior of hadron resonance yields, demonstrating that certain resonances are enhanced or suppressed due to dynamic formation reactions, challenging the assumption of chemical equilibrium.

Contribution

It introduces a dynamic model for resonance formation reactions, showing that resonance yields deviate from equilibrium predictions, with specific examples like $ ext{Sigma}(1385)$ and $ ext{Lambda}(1520)$.

Findings

$ ext{Sigma}(1385)$ is enhanced due to resonance formation.

$ ext{Lambda}(1520)$ is suppressed in non-equilibrium conditions.

Resonance yields generally do not reach chemical equilibrium.

Abstract

We discuss, in qualitative and quantitative fashion, the yields of hadron resonances. We show that these yields, in general, are not in chemical equilibrium. We evaluate the non-equilibrium abundances in a dynamic model implementing the $1+2\leftrightarrow 3$ resonance formation reactions. Due to the strength of these reactions, we show the $\Sigma(1385)$ enhancement, and the $\Lambda(1520)$ suppression explicitly.