  We study a vectorial gauge theory with gauge group SU(Nc) and a variable
number, Nf, of massless fermions in the fundamental representation of this
group. Using approximate solutions of Schwinger-Dyson and Bethe-Salpeter
equations, we calculate meson masses and investigate how these depend on Nf. We
focus on the range of Nf extending from near the boundary with a non-Abelian
Coulomb phase, where the theory exhibits a slowly running ("walking") gauge
coupling, toward smaller values where the theory has non-walking behavior. Our
results include determinations of the masses of the lowest-lying flavor-adjoint
mesons with J^{PC} = 0^{-+}, 1^{--}, 0^{++}, and 1^{++} (the generalized \pi,
\rho, a0, and a1). Related results are given for flavor-singlet mesons and for
the generalization of f_\pi. These results give insight into the change from
walking to non-walking behavior in a gauge theory, as a function of Nf .

High Energy Physics - Phenomenology