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

Abstract

The process e^+e^-rightarrow eta pi ^0gamma 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 ^0gamma 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 ^0gamma is consistent with previous measurements in the e^+e^-rightarrow pi ^+pi ^-pi ^0eta mode. It is found, with a significance of 5.6sigma , that the process e^+e^-rightarrow eta pi ^0gamma 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.