$U(1{)}_A$ axial anomaly, ${\eta }^{\prime }$, and topological susceptibility in the holographic soft-wall model

Abstract

The singlet pseudoscalar sector of light mesons is investigated in the soft-wall model, a bottom-up approach to the AdS/QCD correspondence. The ${\eta }^{\prime }$ mass results from the mixing among the fields dual to the axial current, pseudoscalar current and the $G\tilde{G}$ operator. The topological susceptibility is computed for any quark mass, and the Witten-Veneziano relation is obtained in the large $N_c$ limit.

Comments: 19 pages, 4 figures, new references, modified notation. this version matches the published paper