On the couplings of vector mesons in AdS/QCD

Abstract

We address, in the AdS/CFT context, the issue of the universality of the couplings of the ρ meson to other hadrons. Exploring some models, we find that generically the ρ-dominance prediction f ρg ρHH = m ρ2 does not hold, and that g ρHH is not independent of the hadron H. However, we prove that, in any model within the AdS/QCD context, there are two limiting regimes where the g ρHH, along with the couplings of all excited vector mesons as well, become H-independent: (1) when H is created by an operator of large dimension, and (2) when H is a highly-excited hadron. We also find a sector of a particular model where universality for the ρ coupling is exact. Still, in none of these cases need it be true that f ρg ρ = m ρ2, although we find empirically that the relation does hold approximately (up to a factor of order two) within the models we have studied. © SISSA 2006.