Probing AdS/QCD backgrounds with semi-classical strings

Abstract

New AdS/QCD backgrounds have been proposed to describe the spectrum of heavy vector mesons via the implementation of additional energy scales on the bulk geometry of the soft wall model. The extra energy scales are needed to include the decay constants of hadronic states when describing the radial excitations of the heavy meson. Here we analyze one model that introduces an ultraviolet cutoff on Anti de-Sitter space and a model that consider a dilaton profile modified by the addition of an extra term and no cutoff. For each one of these two models we consider the presence of a semi-classical string in the bulk that is dual to a static and infinitely heavy meson. We compute the expected value of the Wilson loop operator using the holographic dictionary and obtain the dual potential for the static $q\bar{q}$ pair. For the model with modified dilaton profile the on-shell string action presents a peculiar ultraviolet divergence, a compatible regularization is discussed and a new subtraction scheme is used. We consider the case of finite temperature and determine how the dissociation temperature of the heavy meson is affected by the additional energy scales.