2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/187424We study the constraints that the operator product expansion imposes on large $N_c$ inspired QCD models for current-current correlators. We focus on the constraints obtained by going beyond the leading-order parton computation. We explicitly show that, assumed a given mass spectrum: linear Regge behavior in $n$ (the principal quantum number) plus corrections in $1/n$, we can obtain the logarithmic (and constant) behavior in $n$ of the decay constants within a systematic expansion in $1/n$. Our example shows that it is possible to have different large $n$ behavior for the vector and pseudo-vector mass spectrum and yet comply with all the constraints from the operator product expansion.14 pages, 6 figures; two references added, numerical analysis extended, main conclusions unchangedHigh Energy Physics - PhenomenologyHigh Energy Physics - TheoryNuclear Theorytext