On the Couplings of the Rho Meson in AdS/QCD

TL;DR

This paper demonstrates that in AdS/QCD models, the couplings of the rho meson to various hadrons are nearly universal, primarily due to the rho's unique role as the lowest-lying state from a conserved current.

Contribution

It provides a theoretical argument for the quasi-universality of rho meson couplings in AdS/QCD models, extending understanding beyond rho-dominance assumptions.

Findings

Rho meson couplings are quasi-universal near m(rho)^2/f(rho)

Universality holds even when rho-dominance is broken

The argument applies specifically to the lowest-lying spin-two hadron

Abstract

We argue that in generic AdS/QCD models (confining gauge theories dual to string theory on a weakly-curved background), the couplings g_{rho HH} of any rho meson to any hadron H are quasi-universal, lying within a narrow band near m(rho)^2/f(rho). The argument relies upon the fact that the rho is the lowest-lying state created by a conserved current, and the detailed form of the integrals which determine the couplings in AdS/QCD. Quasi-universality holds even when rho-dominance is violated. The argument fails for all other hadrons, except the lowest-lying spin-two hadron created by the energy-momentum tensor. Explicit examples are discussed.