Dispersive analysis of $\eta \to 3\pi$

Gilberto Colangelo, Stefan Lanz, Heinrich Leutwyler +1

The dispersive analysis of the decay $\eta \to 3\pi$ is reviewed and thoroughly updated with the aim of determining the quark mass ratio ~$Q^2=(m_s^2-m_{ud}^2)/(m_d^2-m_u^2)$. With the nu…