Dispersion relations for $\eta'\to\eta\pi\pi$

Understand

We present a dispersive analysis of the decay amplitude for $\eta'\to\eta\pi\pi$ that is based on the fundamental principles of analyticity and unitarity.

• In this framework, final-state interactions are fully taken into account.
• Our dispersive representation relies only on input for the $\pi\pi$ and $\pi\eta$ scattering phase shifts.
• Isospin symmetry allows us to describe both the charged and neutral decay channel in terms of the same function.