2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/51221It is shown that the evaluation of the expectation value (EV) of topological charge density over $θ$-vacuum is reduced to investigation of the Chern-Simons term EV. An equation for this quantity is established and solved. EV of the topological charge density at an arbitrary $θ$ occurs equal to zero and, as a consequence, topological susceptibility of both QCD and pure Yang-Mills vacua defined in a Wick sense is equal to zero, whereas when defined in a Dyson sense it differs from zero by the quantity proportional to the respective condensate of the chromomagnetic field. Thus, the usual Witten-Veneziano formula for the $η^{'}$ meson mass is modified.High Energy Physics - Theorytext