On the extraction of the quark mass ratio (md−mu)/ms from Γ(η′→π0π+π−)/Γ(η′→ηπ+π−)

The claim that the light quark mass ratio (md−mu)/ms can be extracted from the decay width ratio Γ(η′→π0π+π−)/Γ(η′→ηπ+π−) is critically investigated within a U(3) chiral unitary framework. The influence of the recent VES data on the η′→ηπ+π− decay is also discussed.