Study of the process $e^+e^- \to \pi^+\pi^-\eta $ using initial state radiation

Understand

We study the process $e^+e^- \to \pi^+\pi^-\eta \gamma$, where the photon is radiated from the initial state.

• About 8000 fully reconstructed events of this process are selected from the BaBar data sample with an integrated luminosity of 469~fb$^{-1}$.
• Using the $\pi^+\pi^-\eta$ invariant mass spectrum we measure the $e^+e^- \to \pi^+\pi^-\eta$ cross section in the $e^+e^-$ center-of-mass energy range from 1.15 to 3.5 GeV.
• The cross section is well described by the Vector-Meson Dominance model with four $\rho$-like states.