Abstract

We investigate the magnetic susceptibility of the QCD vacuum, based on the instanton vacuum. Starting from the instanton liquid model for the instanton vacuum, we derive the light-quark partition function Z[V,T,m] in the presence of the current quark mass m as well as the external Abelian vector and tensor fields. We calculate a two-point correlation function relevant for the magnetic susceptibility and derive it beyond the chiral limit. We obtain for the different flavors the following magnetic susceptibility: χ_{u,d}〈iψ_{u,d}†ψ_{u,d}〉∼40–45MeV, while χ_s〈iψ_s†ψ_s〉0≃6–10MeV.