Calculation of the chiral Lagrangian coefficients with light vector mesons

TL;DR

This paper computes the low-energy coefficients of the chiral Lagrangian including light vector mesons directly from QCD, extending previous work on pseudo-scalar mesons and validating the approach with sum rules.

Contribution

It presents the first calculation of chiral Lagrangian coefficients for vector mesons from QCD, focusing on parameters a and g, using a cut-off regularization method.

Findings

Regularization with cut-off yields reasonable results for vector mesons.

The method aligns with Weinberg sum rules.

First QCD-based calculation of vector meson coefficients.

Abstract

We calculate the coefficients in the effective chiral Lagrangian from QCD, which includes pseudo-scalar mesons and vector mesons (with hidden symmetry), up to O(p4). This encompasses both the normal and anomalous parts. Our work builds on a previous study that derived the chiral Lagrangian from first principles of QCD, where the low-energy coefficients are defined in terms of specific Green's functions in QCD. This research extends our earlier efforts that focused on calculating the low-energy coefficients of the chiral Lagrangian for pure pseudo-scalar mesons. This marks the first calculation of chiral Lagrangian coefficients for vector mesons from QCD, particularly for the important parameters a and g, which are typically considered inputs in existing literature. Notably, the regularization method used previously is inadequate for this broader scope. We find that cut-off regularization yields reasonable results for both pseudo-scalar mesons and vector mesons, though it has certain limitations. Finally, we demonstrate that our method aligns with the Weinberg sum rules.