A measurement of the reaction e+e- →e+e-η′ and the radiative width Γη′→γγ at petra ☆

Abstract The reaction e+e- → e+e-η' has been observed in the JADE experiment at PETRA, by detecting the final state π+π-γ, resulting from the decay η' → γϱ0. The cross section was measured at an average beam energy of 17.15 GeV to be σ(e+e- → e+e-η') = 2.2 ± 0.2 (stat.) ± 0.4(syst.) nb, yielding the radiative width Γη'γγ= 5.0 ± 0.5(stat.) ± 0.9 (syst.) keV.