Study of the process e+e-→ηηγ in the energy range s=1.17--2.00 GeV with the SND detector

Abstract

The process $e^{+}{e}^{-}\to \eta \eta \gamma$ is studied in the center-of-mass energy range 1.17–2.00 GeV using data with an integrated luminosity of 201 pb${}^{-1}$ collected by the SND detector at the VEPP-2000 $e^{+}{e}^{-}$ collider. The $e^{+}{e}^{-}\to \eta \eta \gamma$ cross section is measured for the first time. It is shown that the dominant mechanism of this reaction is the transition through the $\varphi \eta$ intermediate state. Our result on the $e^{+}{e}^{-}\to \eta \eta \gamma$ cross section is consistent with the $e^{+}{e}^{-}\to \varphi \eta$ measurement in the $\varphi \to K^{+}{K}^{-}$ mode. The search for radiative processes contributing to the $e^{+}{e}^{-}\to \eta \eta \gamma$ cross section is performed, and no significant signal is observed.