QCD spectral sum rules and spontaneously broken chiral symmetry

TL;DR

This paper uses QCD spectral sum rules to analyze the scale of chiral symmetry breaking and its implications for vector meson properties, providing insights into resonance-continuum separation and in-medium mass scaling.

Contribution

It introduces the chiral symmetry breaking scale as a key parameter in QCD sum rules and derives accurate sum rules for spectral moments, clarifying in-medium vector meson mass behavior.

Findings

Chiral symmetry breaking scale is approximately 1.2 GeV.

Sum rules for spectral moments are accurately derived.

In-medium vector meson mass scaling is interpretable in the narrow width limit.

Abstract

The gap Delta = 4 pi f_pi ~ 1.2 GeV of spontaneous chiral symmetry breaking is introduced as a scale delineating resonance and continuum regions in the QCD spectral sum rules for vector mesons. Basic current algebra results are easily recovered, and accurate sum rules for the lower moments of the spectral distributions are derived. The in-medium scaling of vector meson masses finds a straightforward interpretation, at least in the narrow width limit.