On the Evaluation of Gluon Condensate Effects in the Holographic Approach to QCD

TL;DR

This paper develops two methods to evaluate how gluonic condensates affect vector resonance properties in holographic QCD models, improving phenomenological consistency and understanding of the underlying physics.

Contribution

It introduces two equivalent perturbative techniques for calculating gluonic condensate effects on vector resonances in 5D holographic QCD models.

Findings

Gluonic condensate corrections improve model phenomenology

Methods accurately compute decay constants and couplings

Enhances understanding of sum rules in holographic QCD

Abstract

In holographic QCD the effects of gluonic condensate can be encoded in a suitable deformation of the 5D metric. We develop two different methods for the evaluation of first order perturbative corrections to masses and decay constants of vector resonances in 5D Hard-Wall models of QCD due to small deformations of the metric. They are extracted either from a novel compact form for the first order correction to the vector two-point function, or from perturbation theory for vector bound-state eigenfunctions: the equivalence of the two methods is shown. Our procedures are then applied to flat and to AdS 5D Hard-Wall models; we complement results of existing literature evaluating the corrections to vector decay constant and to two-pion-one-vector couplings: this is particularly relevant to satisfy the sum rules. We concentrate our attention on the effects for the Gasser-Leutwyler coefficients; we show that, as in the Chiral Quark model, the addition of the gluonic condensate improves the consistency, the understanding and the agreement with phenomenology of the holographic model.