QCD spectral sum rules 2022

TL;DR

This paper reviews the latest developments in QCD spectral sum rules up to 2022, focusing on parameter determinations and phenomenological applications across various hadronic channels.

Contribution

It provides an updated overview of QCD sum rules, including recent progress in parameter extraction and insights into hybrid meson states.

Findings

Refined estimates of QCD input parameters with correlations considered

Confirmation of the hybrid nature of the $(1600)$ meson

Revised mass estimates for the $1^{-+}$ light hybrid state

Abstract

We present a compact review of the status of QCD spectral sum rules until 2022. We emphasize the recent progresses for determining the QCD input parameters ($\alpha_s$, running quark masses, quark and gluon condensates) where their correlations have been taken into account. Some selected phenomenological uses of the sum rules in different channels (light and heavy quarks, gluonia/glueballs, hybrids and four-quark states) are briefly reviewed and commented. The estimate of the $1^{-+}$ light hybrid mass is revised which confirms the hybrid nature of the $\pi_1(1600)$ but not the $\pi_1(2050)$.