Study of the process $$e^+e^- \rightarrow \eta \eta \gamma $$ in the energy range $$\sqrt{s} = \text{1.17--2.00 }$$ GeV with the SND detector

Abstract

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

Contribution of exclusive $(π^0π^0, π^0η, ηη)γ$ channels to the leading order HVP of the muon $g-2$

“…GeV region have been reported by the SND collaboration [38]. More recently, the first measuments of the ηηγ production cross section were reported in [39].…”