Using a chiral anomaly to determine the number of colors

The Nc dependence of PPPγ vertices, where P is a pseudoscalar meson and Nc is the number of colors, is analyzed with allowance for the Nc dependence of the quark charges. It is shown that the reactions Kγ → Kπ and π±γ → π±η and the decay η → π+π-γ are the best processes for determining Nc. The cross section σ(π-γ → π-η) as measured by using the VES facility at IHEP agrees with the value of Nc = 3