https://vital.lib.tsu.ru/vital/access/manager/Index en-us 5 https://vital.lib.tsu.ru/vital/access/manager/Repository/koha:001007868 e(+)e(-)e(+)e(-) is observed for the first time via the J/psi -> gamma eta' decay process. The significance is found to be 5.7s with systematic uncertainties taken into consideration. Its branching fraction is determined to be B(eta' -> e(+)e(-)e(+)e(-)) = (4.5 +/- 1.0(stat) +/- 0.5(sys)) x 10(-6).]]> Fri 27 Oct 2023 13:41:46 KRAT ]]>