Study of the process $$e^+e^- \rightarrow \eta \pi ^0\gamma $$e+e-→ηπ0γ in the energy range $$\sqrt{s} = {1.05-2.00}$$s=1.05-2.00 GeV with the SND detector

The process $$e^+e^-\rightarrow \eta \pi ^0\gamma $$ is studied in the center-of-mass energy range 1.05–2.00 GeV using data with an integrated luminosity of 94.5 $$\hbox {pb}^{-1}$$ collected by the SND detector at the VEPP-2000 $$e^{+}e^{-}$$ collider. The $$e^+e^-\rightarrow \eta \pi ^0\gamma $$ cross section is measured for the first time. It is shown that the dominant mechanism of this reaction is the transition through the $$\omega \eta $$ intermediate state. The measured cross section of the subprocess $$e^+e^-\rightarrow \omega \eta \rightarrow \eta \pi ^0\gamma $$ is consistent with previous measurements in the $$e^+e^-\rightarrow \pi ^+\pi ^-\pi ^0\eta $$ mode. It is found, with a significance of $$5.6\sigma $$ , that the process $$e^+e^-\rightarrow \eta \pi ^0\gamma $$ is not completely described by hadronic vector-pseudoscalar intermediate states. The cross section of this missing contribution, which can originate from radiation processes, e. g. $$e^+e^-\rightarrow a_{0}(1450)\gamma $$ , is measured. It is found to be 15–20 pb in the wide energy range from 1.3 to 1.9 GeV.